Physics Book - User contributions [en]

Hall Effect

2017-12-02T09:04:27Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

[[File:Screen Shot 2017-12-02 at 3.43.33 AM.png|200px|thumb|left|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.08 AM.png|200px|thumb|right|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.20 AM.png|200px|thumb|right|Hall Effect Sensor pinout]]
Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the pictures to the left and to the right, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the VIP Research: https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction. Another great way of using the hall effect in smartphones is to lock the screen when a case cover is flipped. The cover has a magnet that the smartphone senses, so it locks the screen automatically when the cover is on the screen. A test for this feature can be seen in the following video: https://www.youtube.com/watch?v=ITbT5vrvhX8 .

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

http://www.electronics-tutorials.ws/electromagnetism/hall-effect.html

https://www.quora.com/What-is-the-use-of-Hall-effect-sensors-in-smartphones

[[Category: Hall Effect]]

Hall Effect

2017-12-02T08:58:09Z

Seprudencio: /* References */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

[[File:Screen Shot 2017-12-02 at 3.43.33 AM.png|200px|thumb|left|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.08 AM.png|200px|thumb|right|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.20 AM.png|200px|thumb|right|Hall Effect Sensor pinout]]
Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the pictures to the left and to the right, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the VIP Research: https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

http://www.electronics-tutorials.ws/electromagnetism/hall-effect.html

https://www.quora.com/What-is-the-use-of-Hall-effect-sensors-in-smartphones

[[Category: Hall Effect]]

Hall Effect

2017-12-02T08:53:08Z

Seprudencio: /* References */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

[[File:Screen Shot 2017-12-02 at 3.43.33 AM.png|200px|thumb|left|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.08 AM.png|200px|thumb|right|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.20 AM.png|200px|thumb|right|Hall Effect Sensor pinout]]
Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the pictures to the left and to the right, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the VIP Research: https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

http://www.electronics-tutorials.ws/electromagnetism/hall-effect.html

[[Category: Hall Effect]]

Hall Effect

2017-12-02T08:52:12Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

[[File:Screen Shot 2017-12-02 at 3.43.33 AM.png|200px|thumb|left|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.08 AM.png|200px|thumb|right|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.20 AM.png|200px|thumb|right|Hall Effect Sensor pinout]]
Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the pictures to the left and to the right, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the VIP Research: https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T08:50:45Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

[[File:Screen Shot 2017-12-02 at 3.43.33 AM.png|200px|thumb|left|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.08 AM.png|200px|thumb|center|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.20 AM.png|200px|thumb|right|Hall Effect Sensor pinout]]
Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the picture, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the VIP Research: https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T08:50:09Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

[[File:Screen Shot 2017-12-02 at 3.43.33 AM.png|200px|thumb|left|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.08 AM.png|200px|thumb|left|Hall Effect Sensor with an magnet]]
[[File:Screen Shot 2017-12-02 at 3.43.20 AM.png|200px|thumb|left|Hall Effect Sensor pinout]]
Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the picture, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the VIP Research: https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

File:Screen Shot 2017-12-02 at 3.43.33 AM.png

2017-12-02T08:46:18Z

Seprudencio: Hall Effect Sensor

Hall Effect Sensor

File:Screen Shot 2017-12-02 at 3.43.20 AM.png

2017-12-02T08:45:35Z

Seprudencio: Hall Effect Sensor pins

Hall Effect Sensor pins

File:Screen Shot 2017-12-02 at 3.43.08 AM.png

2017-12-02T08:44:54Z

Seprudencio: Hall Effect Sensor

Hall Effect Sensor

Hall Effect

2017-12-02T08:42:47Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the picture, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the VIP Research: https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T08:42:19Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the picture, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the ====VIP Research:==== https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T08:41:09Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, one of the ways it is used is as a motion sensor, as described below.

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Another field that takes advantage of the Hall Effect is Electrical Engineering thanks to the Hall Effect Sensor. Electrical engineers can use the hall effect sensor to record movement. As seen in the picture, the sensor will increase its voltage the closer the magnet is to the sensor. In fact, a VIP group here at Georgia Tech, the VIP Hands-on Learning team, researched the possibility of using the sensor to measure the movement of a two-degree of freedom spring-mass system.
Links to the VIP Research: https://vip.gatech.edu/wiki/index.php/Vibrations https://vip.gatech.edu/wiki/index.php/Hall_Effect_Sensor

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes. Every smartphone today uses a hall effect sensor as well. This is how the digital compass of a cell phone works. The hall effect senses the change in magnetic field to approximate direction.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T08:21:48Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
====How is this topic connected to something that you are interested in?====

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the Hall Effect Sensor. It is a small sensor that will output a difference in voltage depending on the change in the magnetic field near the sensor. Thanks to this, t

====How is it connected to your major?====

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevance to my major. Moreover, a lot of engineering, in general, is about analyzing concepts before calculating values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info on the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

====Is there an interesting industrial application?====

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create a circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right-hand rule. Use this information to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T07:04:58Z

Seprudencio: /* Connectedness */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the [[Hall Effect Sensor|Hall Effect Sensor]].

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T07:00:12Z

Seprudencio: /* Connectedness */ I changed the format of a previous statement to a more professional wording.

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

The Hall Effect can be as enjoyable as a puzzle. One has to pull the threads with all of the information that is given and connect the dots. Several key physics laws have to be applied, and the results can be quite practical.
One practical application of the Hall Effect is the [[Hall Effect Sensor]].

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T06:28:09Z

Seprudencio: /* History */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T06:25:56Z

Seprudencio: /* References */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Herbert Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hall-edwin.pdf

[[Category: Hall Effect]]

Hall Effect

2017-12-02T06:22:51Z

Seprudencio: /* History */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by [[Edwin Herbert Hall]] while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Hall Effect

2017-12-02T06:09:34Z

Seprudencio: /* History */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by Edwin Herbert Hall while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery of the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Hall Effect

2017-12-02T06:08:10Z

Seprudencio: /* History */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg|thumb|right|Edwin Herbert Hall]]

The Hall Effect was discovered in 1879 by Edwin Herbert Hall while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow as usual. This is what led to Hall's discovery o the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right-hand rule whenever in doubt.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Hall Effect

2017-12-02T06:05:59Z

Seprudencio: /* Explore its application in a lab setting?? */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg]]

The Hall Effect was discovered in 1879 by Edwin Herbert Hall while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow like usual. This is what led to Hall's discovery o the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right hand rule whenever in doubt.
== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Hall Effect

2017-12-02T06:04:47Z

Seprudencio: /* Middling */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.
</div>
</div>

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting??===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg]]

The Hall Effect was discovered in 1879 by Edwin Herbert Hall while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow like usual. This is what led to Hall's discovery o the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right hand rule whenever in doubt.
== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Hall Effect

2017-12-02T06:03:53Z

Seprudencio: /* Simple */

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

<div class="toccolours mw-collapsible mw-collapsed">

'''''Click for Solution'''''
<div class="mw-collapsible-content">
In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.

</div>
</div>

===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

Answer: First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting??===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg]]

The Hall Effect was discovered in 1879 by Edwin Herbert Hall while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow like usual. This is what led to Hall's discovery o the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right hand rule whenever in doubt.
== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Main Page

2017-12-02T05:58:07Z

Seprudencio: /* Week 10 */

__NOTOC__
= '''Georgia Tech Student Wiki for Introductory Physics.''' =

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== Source Material ==
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* A physics resource written by experts for an expert audience [https://en.wikipedia.org/wiki/Portal:Physics Physics Portal]
* A wiki written for students by a physics expert [http://p3server.pa.msu.edu/coursewiki/doku.php?id=183_notes MSU Physics Wiki]
* A wiki book on modern physics [https://en.wikibooks.org/wiki/Modern_Physics Modern Physics Wiki]
* The MIT open courseware for intro physics [http://ocw.mit.edu/resources/res-8-002-a-wikitextbook-for-introductory-mechanics-fall-2009/index.htm MITOCW Wiki]
* An online concept map of intro physics [http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html HyperPhysics]
* Interactive physics simulations [https://phet.colorado.edu/en/simulations/category/physics PhET]
* OpenStax intro physics textbooks: [https://openstax.org/details/books/university-physics-volume-1 Vol1], [https://openstax.org/details/books/university-physics-volume-2 Vol2], [https://openstax.org/details/books/university-physics-volume-3 Vol3]
* The Open Source Physics project is a collection of online physics resources [http://www.opensourcephysics.org/ OSP]
* A resource guide compiled by the [http://www.aapt.org/ AAPT] for educators [http://www.compadre.org/ ComPADRE]
* The Feynman lectures on physics are free to read [http://www.feynmanlectures.caltech.edu/ Feynman]

== Resources ==
* Commonly used wiki commands [https://en.wikipedia.org/wiki/Help:Cheatsheet Wiki Cheatsheet]
* A guide to representing equations in math mode [https://en.wikipedia.org/wiki/Help:Displaying_a_formula Wiki Math Mode]
* A page to keep track of all the physics [[Constants]]
* A page for review of [[Vectors]] and vector operations
* A listing of [[Notable Scientist]] with links to their individual pages

<div style="float:left; width:30%; padding:1%;">
==Physics 1==
===Week 1===
<div class="toccolours mw-collapsible mw-collapsed">
====Help with VPython====
<div class="mw-collapsible-content">
*[[Python Syntax]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Vectors and Units====

<div class="mw-collapsible-content">
*[[Vectors]]
*[[SI Units]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====VPython====

<div class="mw-collapsible-content">
*[[VPython]]
*[[VPython basics]]
*[[VPython Common Errors and Troubleshooting]]
*[[VPython Functions]]
*[[VPython Lists]]
*[[VPython Loops]]
*[[VPython Multithreading]]
*[[VPython Animation]]
*[[VPython Objects]]
*[[VPython 3D Objects]]
*[[VPython Reference]]
*[[VPython MapReduceFilter]]
*[[VPython GUIs]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Vectors and Units====
<div class="mw-collapsible-content">
*[[Vectors]]
*[[SI Units]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Interactions====
<div class="mw-collapsible-content">
*[[Types of Interactions and How to Detect Them]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Velocity and Momentum====
<div class="mw-collapsible-content">
*[[Newton's First Law of Motion]]
*[[Velocity]]
*[[Mass]]
*[[Speed and Velocity]]
*[[Relative Velocity]]
*[[Derivation of Average Velocity]]
*[[2-Dimensional Motion]]
*[[3-Dimensional Position and Motion]]
</div>
</div>

===Week 2===
<div class="toccolours mw-collapsible mw-collapsed">
====Momentum and the Momentum Principle====
<div class="mw-collapsible-content">
*[[Momentum Principle]]
*[[Inertia]]
*[[Net Force]]
*[[Derivation of the Momentum Principle]]
*[[Impulse Momentum]]
*[[Acceleration]]
*[[Momentum with respect to external Forces]]
*[[Relativistic Momentum]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Iterative Prediction with a Constant Force====
<div class="mw-collapsible-content">
*[[Newton’s Second Law of Motion]]
*[[Iterative Prediction]]
*[[Kinematics]]
*[[Newton’s Laws and Linear Momentum]]
*[[Projectile Motion]]
</div>
</div>

===Week 3===
<div class="toccolours mw-collapsible mw-collapsed">

====Analytic Prediction with a Constant Force====
<div class="mw-collapsible-content">
*[[Analytical Prediction]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Iterative Prediction with a Varying Force====
<div class="mw-collapsible-content">
*[[Predicting Change in multiple dimensions]]
*[[Spring Force]]
*[[Hooke's Law]]
*[[Simple Harmonic Motion]]
*[[Iterative Prediction of Spring-Mass System]]
*[[Terminal Speed]]
*[[Determinism]]
</div>
</div>

===Week 4===
<div class="toccolours mw-collapsible mw-collapsed">
====Fundamental Interactions====
<div class="mw-collapsible-content">

==Main Idea==

*[[Gravitational Force]]
*[[Fluid Mechanics]]
*[[An Application of Gravitational Potential]]
*[[Electric Force]]
*[[Reciprocity]]
</div>
</div>

===Week 5===
<div class="toccolours mw-collapsible mw-collapsed">
====Conservation of Momentum====
<div class="mw-collapsible-content">
*[[Conservation of Momentum]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">

====Properties of Matter====
<div class="mw-collapsible-content">
*[[Kinds of Matter]]
*[[Ball and Spring Model of Matter]]
*[[Density]]
*[[Length and Stiffness of an Interatomic Bond]]
*[[Young's Modulus]]
*[[Speed of Sound in Solids]]
*[[Malleability]]
*[[Ductility]]
*[[Weight]]
*[[Hardness]]
*[[Boiling Point]]
*[[Melting Point]]
*[[Change of State]]
</div>
</div>

===Week 6===
<div class="toccolours mw-collapsible mw-collapsed">
====Identifying Forces====
<div class="mw-collapsible-content">
*[[Free Body Diagram]]
*[[Inclined Plane]]
*[[Compression or Normal Force]]
*[[Tension]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">

====Curving Motion====
<div class="mw-collapsible-content">
*[[Curving Motion]]
*[[Centripetal Force and Curving Motion]]
*[[Perpetual Freefall (Orbit)]]
</div>
</div>

===Week 7===
<div class="toccolours mw-collapsible mw-collapsed">
====Energy Principle====
<div class="mw-collapsible-content">
*[[The Energy Principle]]
*[[Conservation of Energy]]
*[[Kinetic Energy]]
*[[Work]]
*[[Power (Mechanical)]]
</div>
</div>

===Week 8===
<div class="toccolours mw-collapsible mw-collapsed">
====Work by Non-Constant Forces====
<div class="mw-collapsible-content">
*[[Work Done By A Nonconstant Force]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Potential Energy====
<div class="mw-collapsible-content">
*[[Potential Energy]]
*[[Potential Energy of Macroscopic Springs]]
*[[Spring Potential Energy]]
*[[Ball and Spring Model]]
*[[Gravitational Potential Energy]]
*[[Energy Graphs]]
*[[Escape Velocity]]
</div>
</div>

===Week 9===
<div class="toccolours mw-collapsible mw-collapsed">
====Multiparticle Systems====
<div class="mw-collapsible-content">
*[[Center of Mass]]
*[[Multi-particle analysis of Momentum]]
*[[Momentum with respect to external Forces]]
*[[Potential Energy of a Multiparticle System]]
*[[Work and Energy for an Extended System]]
*[[Internal Energy]]
**[[Potential Energy of a Pair of Neutral Atoms]]
</div>
</div>

===Week 10===
<div class="toccolours mw-collapsible mw-collapsed">
====Choice of System====
<div class="mw-collapsible-content">
*[[System & Surroundings]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Thermal Energy, Dissipation and Transfer of Energy====
<div class="mw-collapsible-content">
*[[Thermal Energy]]
*[[Specific Heat]]
*[[Heat Capacity]]
*[[Calorific Value(Heat of combustion)]]
*[[Specific Heat Capacity]]
*[[First Law of Thermodynamics]]
*[[Second Law of Thermodynamics and Entropy]]
*[[Temperature]]
*[[Predicting Change]]
*[[Energy Transfer due to a Temperature Difference]]
*[[Transformation of Energy]]
*[[The Maxwell-Boltzmann Distribution]]
*[[Air Resistance]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">

====Rotational and Vibrational Energy====
<div class="mw-collapsible-content">
*[[Translational, Rotational and Vibrational Energy]]
</div>
</div>

===Week 11===
<div class="toccolours mw-collapsible mw-collapsed">
====Different Models of a System====
<div class="mw-collapsible-content">
*[[Point Particle Systems]]
*[[Real Systems]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Models of Friction====
<div class="mw-collapsible-content">
*[[Friction]]
*[[Static Friction]]
</div>
</div>

===Week 12===
<div class="toccolours mw-collapsible mw-collapsed">
====Collisions====
<div class="mw-collapsible-content">
*[[Newton's Third Law of Motion]]
*[[Collisions]]
*[[Elastic Collisions]]
*[[Inelastic Collisions]]
*[[Maximally Inelastic Collision]]
*[[Head-on Collision of Equal Masses]]
*[[Head-on Collision of Unequal Masses]]
*[[Scattering: Collisions in 2D and 3D]]
*[[Rutherford Experiment and Atomic Collisions]]
*[[Coefficient of Restitution]]
</div>
</div>

===Week 13===
<div class="toccolours mw-collapsible mw-collapsed">
====Rotations====
<div class="mw-collapsible-content">
*[[Rotation]]
*[[Angular Velocity]]
*[[Eulerian Angles]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Angular Momentum====
<div class="mw-collapsible-content">
*[[Total Angular Momentum]]
*[[Translational Angular Momentum]]
*[[Rotational Angular Momentum]]
*[[The Angular Momentum Principle]]
*[[Angular Momentum Compared to Linear Momentum]]
*[[Angular Impulse]]
*[[Predicting the Position of a Rotating System]]
*[[Angular Momentum of Multiparticle Systems]]
*[[The Moments of Inertia]]
*[[Moment of Inertia for a cylinder]]
*[[Right Hand Rule]]
</div>
</div>

===Week 14===
<div class="toccolours mw-collapsible mw-collapsed">
====Analyzing Motion with and without Torque====
<div class="mw-collapsible-content">
*[[Torque]]
*[[Torque 2]]
*[[Systems with Zero Torque]]
*[[Systems with Nonzero Torque]]
*[[Torque vs Work]]
*[[Gyroscopes]]
</div>
</div>

===Week 15===
<div class="toccolours mw-collapsible mw-collapsed">
====Introduction to Quantum Concepts====
<div class="mw-collapsible-content">
*[[Bohr Model]]
*[[Energy graphs and the Bohr model]]
*[[Quantized energy levels]]
*[[Quantized energy levels part II]]
*[[Entropy]]
</div>
</div>
</div>

<div style="float:left; width:30%; padding:1%;">

==Physics 2==
===Week 1===
<div class="toccolours mw-collapsible mw-collapsed">
====3D Vectors====
<div class="mw-collapsible-content">
*[[Vectors]]
*[[Right-Hand Rule]]
*[[Right Hand Rule]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Electric field====
<div class="mw-collapsible-content">
*[[Electric Field]]
*[[Electric Field and Electric Potential]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Electric force====
<div class="mw-collapsible-content">
*[[Electric Force]]
*[[Lorentz Force]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Electric field of a point particle====
<div class="mw-collapsible-content">
*[[Point Charge]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Superposition====
<div class="mw-collapsible-content">
*[[Superposition Principle]]
*[[Superposition principle]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Dipoles====
<div class="mw-collapsible-content">
*[[Electric Dipole]]
*[[Magnetic Dipole]]
</div>
</div>

===Week 2===
<div class="toccolours mw-collapsible mw-collapsed">
====Interactions of charged objects====
<div class="mw-collapsible-content">
*[[Electric Field]]
*[[Electric Potential]]
*[[Electric Force]]
*[[Lorentz Force]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Tape experiments====
<div class="mw-collapsible-content">
*[[Polarization]]
*[[Electric Polarization]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Polarization====
<div class="mw-collapsible-content">
*[[Polarization]]
*[[Electric Polarization]]
*[[Polarization of an Atom]]
</div>
</div>

===Week 3===
<div class="toccolours mw-collapsible mw-collapsed">
====Insulators====
<div class="mw-collapsible-content">
*[[Insulators]]
*[[Potential Difference in an Insulator]]
*[[Charged Conductor and Charged Insulator]]
*[[Charged conductor and charged insulator]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Conductors====
<div class="mw-collapsible-content">
*[[Conductivity]]
*[[Charge Transfer]]
*[[Resistivity]]
*[[Polarization of a conductor]]
*[[Charged Conductor and Charged Insulator]]
*[[Charged conductor and charged insulator]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Charging and discharging====
<div class="mw-collapsible-content">
*[[Charge Transfer]]
*[[Electrostatic Discharge]]
*[[Charged Conductor and Charged Insulator]]
*[[Charged conductor and charged insulator]]
</div>
</div>

===Week 4===
<div class="toccolours mw-collapsible mw-collapsed">
====Field of a charged rod====
<div class="mw-collapsible-content">
*[[Charged Rod]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Field of a charged ring/disk/capacitor====
<div class="mw-collapsible-content">
*[[Charged Ring]]
*[[Charged Disk]]
*[[Charged Capacitor]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Field of a charged sphere====
<div class="mw-collapsible-content">
*[[Charged Spherical Shell]]
*[[Field of a Charged Ball]]
</div>
</div>

===Week 5===
<div class="toccolours mw-collapsible mw-collapsed">
====Potential energy====
<div class="mw-collapsible-content">
*[[Potential Energy - Claimed by Janki Patel]]
Morgan Kehoe Spring 2017
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Electric potential====
<div class="mw-collapsible-content">
*[[Electric Potential]]
*[[Path Independence of Electric Potential]]
*[[Potential Difference Path Independence, claimed by Aditya Mohile]]
*[[Potential Difference in a Uniform Field]]
*[[Potential Difference of Point Charge in a Non-Uniform Field]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Sign of a potential difference====
<div class="mw-collapsible-content">
*[[Sign of a Potential Difference]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Potential at a single location====
<div class="mw-collapsible-content">
*[[Electric Potential]]
*[[Potential Difference at One Location]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Path independence and round trip potential====
<div class="mw-collapsible-content">
*[[Path Independence of Electric Potential]]
*[[Potential Difference Path Independence, claimed by Aditya Mohile]]
</div>
</div>

===Week 6===
<div class="toccolours mw-collapsible mw-collapsed">
====Electric field and potential in an insulator====
<div class="mw-collapsible-content">
*[[Potential Difference in an Insulator]]
*[[Electric Field in an Insulator]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Moving charges in a magnetic field====
<div class="mw-collapsible-content">
*[[Magnetic Field]]
*[[Magnetic Force]]
*[[Lorentz Force]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Biot-Savart Law====
<div class="mw-collapsible-content">
*[[Biot-Savart Law]]
*[[Biot-Savart Law for Currents]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
====Moving charges, electron current, and conventional current====
<div class="mw-collapsible-content">
*[[Moving Point Charge]]
*[[Current]]
</div>
</div>

===Week 7===
<div class="toccolours mw-collapsible mw-collapsed">
====Magnetic field of a wire====
<div class="mw-collapsible-content">
*[[Magnetic Field of a Long Straight Wire]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Magnetic field of a current-carrying loop====
<div class="mw-collapsible-content">
*[[Magnetic Field of a Loop]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Magnetic field of a Charged Disk====
<div class="mw-collapsible-content">
*[[Magnetic Field of a Disk]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Magnetic dipoles====
<div class="mw-collapsible-content">
*[[Magnetic Dipole Moment]]
*[[Bar Magnet]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Atomic structure of magnets====
<div class="mw-collapsible-content">
*[[Atomic Structure of Magnets]]
</div>
</div>

===Week 8===
<div class="toccolours mw-collapsible mw-collapsed">
====Steady state current====
<div class="mw-collapsible-content">
*[[Steady State]]
*[[Non Steady State]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Node rule====
<div class="mw-collapsible-content">
*[[Node Rule]]

====The Main Idea====
*'''Mathematical Model'''

**In this image, you can see what our equations are based on: [[File:noderule.jpg]]
**The node rules can be written as I_total = I_1 + I_2 and I_total = I_3 + I_4. It is also true that I_1 + I_2 = I_3 + I_4.
**However, each of these currents are different because each point has a different resistance. The current is different for each because it is equal to V/R, and in a parallel circuit, the voltage drop across each point is equal.
**An easy way to know when to use node rule is by seeing if there are three connections or more. That is when node rule is most helpful.

*'''Computational Model'''

**In an electric circuit in series, electrons flow from the negative end of a power source, creating a constant current. This current remains consistent at each point in the circuit in series. Sometimes, a circuit is not simply one constant path and may include parts that are in parallel, where the current must travel down two paths such as this:
**[[File:noderule.jpg]]
**In this case, when the current enters a portion of the circuit where the items are in parallel, the total amount of current in must equal the total amount of current out. Therefore, the currents in each branch of the parallel portion must sum up to the amount of current at any other point in series in the circuit.
**People also call this the "Junction Rule"
**Another important point is that this comes from the Kirchoff's Circuit Laws

====Examples====

*'''Simple'''
**Here is an example of a simple circuit problem: [[File:SimpleNodeRule.jpg]]

*'''Medium'''
**Here is an example of a medium circuit problem: [[File:MediumNodeRule.jpg]]

*'''Difficult'''
**Here is an example of a difficult circuit problem: [[File:DifficultNodeRule.jpg]]

====Connectedness====

*'''To other topics:'''
**Many times when you use Node Rule you will also use the Loop Rule. The Loop Rule states that the sum of voltage will equal zero. So using this concept and the Node Rule, you are usually able to figure out missing variables in circuit problems.

*'''To majors:'''
**Node rule is important in all and any major. More specifically, electrical engineering because of the constant need to look, analyze, and understand circuits. However, in general, any major that involves some sort of circuitry will need this. It is the basis to making an effective circuit.

*'''To industrial application:'''
**If you go into robots, engineering, or really anything that involves wires and batteries. You will need to know this.

====History====

*Basic History
**Gustav Kirchoff was the man who discovered this rule while studying electrical currents. He was also the first person to confirm an electrical impulse moves at the speed of light.

====External Resources and Information====

*Sources like Khan Academy and simple YouTube searches can be very helpful in learning more about this topic.

</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Electric fields and energy in circuits====
<div class="mw-collapsible-content">
*[[Series circuit]]
*[[Node Rule]]
*[[Loop Rule]]
*[[Electric Potential Difference]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Macroscopic analysis of circuits====
<div class="mw-collapsible-content">
*[[Series Circuits]]
*[[Parallel Circuits]]
*[[Parallel Circuits vs. Series Circuits*]]
*[[Loop Rule]]
*[[Node Rule]]
*[[Fundamentals of Resistance]]
*[[Problem Solving]]
</div>
</div>

===Week 9===
<div class="toccolours mw-collapsible mw-collapsed">
====Electric field and potential in circuits with capacitors====
<div class="mw-collapsible-content">
*[[Charging and Discharging a Capacitor]]
*[[RC Circuit]]
*[[R Circuit]]
*[[AC and DC]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Magnetic forces on charges and currents====
<div class="mw-collapsible-content">
*[[Magnetic Force]]
*[[Lorentz Force]]
*[[Motors and Generators]]
*[[Applying Magnetic Force to Currents]]
*[[Magnetic Force in a Moving Reference Frame]]
*[[Right-Hand Rule]]
*[[Analysis of Railgun vs Coil gun technologies]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Electric and magnetic forces====
<div class="mw-collapsible-content">
*[[Electric Force]]
*[[Magnetic Force]]
*[[Lorentz Force]]
*[[VPython Modelling of Electric and Magnetic Forces]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Velocity selector====
<div class="mw-collapsible-content">
*[[Lorentz Force]]
*[[Combining Electric and Magnetic Forces]]
</div>
</div>

===Week 10===
<div class="toccolours mw-collapsible mw-collapsed">

====Hall Effect====
<div class="mw-collapsible-content">
*[[Hall Effect]]
*[[Right-Hand Rule]]
*[[Motional Emf]]
*[[Magnetic Force]]
*[[Magnetic Torque]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Motional EMF====
<div class="mw-collapsible-content">
*[[Motional Emf]]
*[[Motional Emf using Faraday's Law]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Magnetic force====
<div class="mw-collapsible-content">
*[[Magnetic Force]]
*[[Lorentz Force]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Magnetic torque====
<div class="mw-collapsible-content">
*[[Magnetic Torque]]
*[[Right-Hand Rule]]
</div>
</div>

===Week 12===

<div class="toccolours mw-collapsible mw-collapsed">
====Gauss's Law====
<div class="mw-collapsible-content">
*[[Gauss's Flux Theorem]]
*[[Gauss's Law]]
*[[Magnetic Flux]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Ampere's Law====
<div class="mw-collapsible-content">
*[[Ampere's Law]]
*[[Ampere-Maxwell Law]]
*[[Magnetic Field of Coaxial Cable Using Ampere's Law]]
*[[Magnetic Field of a Long Thick Wire Using Ampere's Law]]
*[[Magnetic Field of a Toroid Using Ampere's Law]]
*[[Magnetic Field of a Solenoid Using Ampere's Law]]
*[[The Differential Form of Ampere's Law]]
</div>
</div>

===Week 13===
<div class="toccolours mw-collapsible mw-collapsed">
====Semiconductors====
<div class="mw-collapsible-content">
*[[Semiconductor Devices]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Faraday's Law====
<div class="mw-collapsible-content">
*[[Faraday's Law]]
*[[Motional Emf using Faraday's Law]]
*[[Lenz's Law]]

</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Maxwell's equations====
<div class="mw-collapsible-content">
*[[Gauss's Law]]
*[[Magnetic Flux]]
*[[Ampere's Law]]
*[[Faraday's Law]]
*[[Maxwell's Electromagnetic Theory]]
</div>
</div>

===Week 14===
<div class="toccolours mw-collapsible mw-collapsed">
====Circuits revisited====
<div class="mw-collapsible-content">

</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

====Inductors====
<div class="mw-collapsible-content">
*[[Inductors]]
*[[Current in an LC Circuit]]
*[[Current in an RL Circuit]]
</div>
</div>

===Week 15===
<div class="toccolours mw-collapsible mw-collapsed">
==== Electromagnetic Radiation ====
<div class="mw-collapsible-content">
*[[Electromagnetic Radiation]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Sparks in the air====
<div class="mw-collapsible-content">
*[[Sparks in Air]]
*[[Spark Plugs]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">
====Superconductors====
<div class="mw-collapsible-content">
*[[Superconducters]]
*[[Superconductors]]
*[[Meissner effect]]
</div>
</div>
</div>

<div style="float:left; width:30%; padding:1%;">

==Physics 3==

===Week 1===
<div class="toccolours mw-collapsible mw-collapsed">
====Classical Physics====
<div class="mw-collapsible-content">
</div>
</div>

===Week 2===
<div class="toccolours mw-collapsible mw-collapsed">
====Special Relativity====
<div class="mw-collapsible-content">
*[[Frame of Reference]]
*[[Einstein's Theory of Special Relativity]]
*[[Time Dilation]]
*[[Einstein's Theory of General Relativity]]
*[[Albert A. Micheleson & Edward W. Morley]]
*[[Magnetic Force in a Moving Reference Frame]]
</div>
</div>

===Week 3===
<div class="toccolours mw-collapsible mw-collapsed">
====Photons====
<div class="mw-collapsible-content">
*[[Spontaneous Photon Emission]]
*[[Light Scattering: Why is the Sky Blue]]
*[[Lasers]]
*[[Electronic Energy Levels and Photons]]
*[[Quantum Properties of Light]]
</div>
</div>

===Week 4===
<div class="toccolours mw-collapsible mw-collapsed">
====Matter Waves====
<div class="mw-collapsible-content">
*[[Wave-Particle Duality]]
</div>
</div>

===Week 5===
<div class="toccolours mw-collapsible mw-collapsed">
====Wave Mechanics====
<div class="mw-collapsible-content">
*[[Standing Waves]]
*[[Wavelength]]
*[[Wavelength and Frequency]]
*[[Mechanical Waves]]
*[[Transverse and Longitudinal Waves]]
</div>
</div>

===Week 6===
<div class="toccolours mw-collapsible mw-collapsed">
====Rutherford-Bohr Model====
<div class="mw-collapsible-content">
*[[Rutherford Experiment and Atomic Collisions]]
*[[Bohr Model]]
*[[Quantized energy levels]]
*[[Energy graphs and the Bohr model]]
</div>
</div>

===Week 7===
<div class="toccolours mw-collapsible mw-collapsed">
====The Hydrogen Atom====
<div class="mw-collapsible-content">
*[[Quantum Theory]]
*[[Atomic Theory]]
</div>
</div>

===Week 8===
<div class="toccolours mw-collapsible mw-collapsed">
====Many-Electron Atoms====
<div class="mw-collapsible-content">
*[[Quantum Theory]]
*[[Atomic Theory]]
*[[Pauli exclusion principle]]
</div>
</div>

===Week 9===
<div class="toccolours mw-collapsible mw-collapsed">
====Molecules====
<div class="mw-collapsible-content">
</div>
</div>

===Week 10===
<div class="toccolours mw-collapsible mw-collapsed">
====Statistical Physics====
<div class="mw-collapsible-content">
</div>
</div>

===Week 11===
<div class="toccolours mw-collapsible mw-collapsed">
====Condensed Matter Physics====
<div class="mw-collapsible-content">
</div>
</div>

===Week 12===
<div class="toccolours mw-collapsible mw-collapsed">
====The Nucleus====
<div class="mw-collapsible-content">
*[[Nucleus]]
</div>
</div>

===Week 13===
<div class="toccolours mw-collapsible mw-collapsed">
====Nuclear Physics====
<div class="mw-collapsible-content">
*[[Nuclear Fission]]
*[[Nuclear Energy from Fission and Fusion]]
</div>
</div>

===Week 14===
<div class="toccolours mw-collapsible mw-collapsed">
====Particle Physics====
<div class="mw-collapsible-content">
*[[Elementary Particles and Particle Physics Theory]]
*[[String Theory]]
</div>
</div>
</div>

Main Page

2017-12-02T05:57:47Z

Seprudencio: /* Hall Effect */

Hall Effect

2017-12-02T05:52:57Z

Seprudencio:

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

Answer: In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.
===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

Answer: First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting??===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg]]

The Hall Effect was discovered in 1879 by Edwin Herbert Hall while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow like usual. This is what led to Hall's discovery o the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right hand rule whenever in doubt.
== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Hall Effect

2017-12-02T05:40:09Z

Seprudencio: Undo revision 31026 by Seprudencio (talk)

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

Answer: In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.
===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

Answer: First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting??===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg]]

The Hall Effect was discovered in 1879 by Edwin Herbert Hall while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow like usual. This is what led to Hall's discovery o the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right hand rule whenever in doubt.
== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Hall Effect

2017-12-02T05:37:38Z

Seprudencio:

Claimed by Katherine Freesemann

edited by Tim Reardon

edited by Megan Walden

edited by Morgan Mango (Spring 2017)

edited by Sergio Prudencio (Fall 2017)

The hall effect is the difference across an electrical conductor. transversal to a electrical current. This is information covered in Chapter 20 of your textbook (Modern Students) and chapter 23 (Classical).

The Hall Effect uses the idea of Fnet being equal and Fnet being the Lorentz Force in these "Hall Effect" questions. This Fnet of zero is achieved due to the polarization properties of metal. Using what we know about how to calculate the Lorentz Force, we can determine things such as the sign of a mobile charge carrier. The Hall Voltage (which is not discussed in this Wiki Page) is a continuation of this idea of the Hall Effect and can be used to determine things such as the density of a mobile charge and can provide more information about the perpendicular electric field. This page is mainly about observations that can be made using Hall Effect without even having to calculate numbers. It is fundamental to understand this page before moving on to calculations with the Hall Effect.

==The Main Idea==

When a mobile charge flows through a wire or metal block and are also influenced by a magnetic force, the mobile charges begin to build up on one side or the other of the block. Because metals have the unique ability to have very mobile charges (unlike insulators) the block polarizes and has negative charges on one side and positive on the other so that the block is able to remain neutral. This grouping of positive charges in one part of the block and negative charges in another part of the block creates an electric field and thus an electric force perpendicular to the flow of the mobile charges through the wire. The magnetic and electric forces cancel each other out and after some time, the charges flow right through the block and do not group on one side or the other of the block. This perpendicular electric field also creates a potential difference known as the "Hall Voltage."

===Part 1: Normal circuit (No Magnetic Field Yet)===
(For simplicity, the mobile charges have already been determined to be negatively charged electrons. This will not always be the case and it should not be assumed that the mobile charges are electrons)

Mobile electrons flow through a wire due to a parallel electric field inside the wire. This electric field is caused by an energy source such as a battery or power supply. The parallel electric field flows from an area of high potential (i.e. the positive end of the battery) to an area of low potential (i.e. the negative end of the battery). This is the same direction as the conventional current. Since electrons are negatively charged, they flow in the opposite direction of the parallel electric field. This can be summarized by the equation:

[[File:Electric_force.png]]

=== Part 2: Initial Transient State (Magnetic Field Present) ===

Mobile electrons are subjected to a magnetic field as they flow through the wire. Since electrons are negatively charged, they experience a magnetic force in the downward direction due to the magnetic field. This can be summarized by the equation:

[[File:Mag_force.png]]

See aside for extra help on determining this direction.

===Part 3: Steady State (Magnetic Field Still Present)===

Over time more and more charges are going to build up. As they build up, they will begin to create a charged area on one surface of the conductor. This charged surface will start to oppose the magnetic force that is holding the electrons. Essentially the electrons are being held against the side of the conductor by the magnetic force. As more and more electrons collect together against the surface of the conductor, they start to oppose the magnetic force that’s holding them. This opposing force is called the transverse electric force and is responsible for the existence of the perpendicular electric field. When enough electrons have collected, their combined transverse electric force will be equal in magnitude to the magnetic force that is holding them. At this point, there is no net vertical force pushing more electrons against the surface of the conductor and these electrons will flow normally again. This is called the steady state. As long as the magnetic field remains the same magnitude and in the same direction and the same number of electrons remain pushed against the conductor’s surface, the steady state will be maintained.

[[File:F_perp.png]]

==== Aside: Right Hand Rule====

ASIDE: The Right Hand Rule is necessary to use in determining the direction that the magnetic force will point. This is also a great trick to determine the answer to other cross products used in the physics course. First, take your right hand and point your thumb in the direction that the mobile charges are flowing. In this case, this would be the direction that the electrons are flowing. Now with your thumb in that direction, point your index finger in the direction of the magnetic field (in this case, the magnetic field would point in into the page as is shown). Now the most important part; point the rest of your fingers so they are coming straight out of your palm. These fingers are pointing in the direction of the magnetic force FOR A POSITIVE CHARGE. Since we have electrons, the magnetic force will point in the exact opposite way. THIS LAST PART IS EXTREMELY IMPORTANT TO REMEMBER. If it makes it easier, you can do the same technique that was used for the right hand with your left hand anytime you have a negative charge.

===A Mathematical Model===

What are the mathematical equations that allow us to model this topic. <math>\vec{F}_{magnetic}= \vec{F}_{electricperpendicular}</math> where '''F_magnetic''' is the force on the mobile charge by the magnetic field and '''F_electricperpendicular''' is the force the mobile charge experiences that is caused by the polarization of the metal.

===A Diagram of How the Hall Effect Works===

In this diagram, I assumed that the mobile charge carrier was positive.

[[File: Diagram1.JPG]]

[[File: Diagram2.jpg]]

==Examples==

The following are 3 examples that help to reinforce the concepts of the Hall Effect. Just like this page, they are all conceptual, so make sure to understand these examples before doing calculation using the Hall effect.

===Simple===

Question: A metal slab is connected to a battery by two wires. Conventional current flows clockwise and the mobile charge in the block is positive. The block also experiences a magnetic field out of the page. The slab is also connected to a voltmeter.The positive end of the voltmeter is connected to the bottom of the block and the negative end of the voltmeter is connected to the top of the block. See attached photo for a diagram.

[[File:HallEffectDiagram.JPG]]

Answer: In order to determine this, we must determine what direction the magnetic force is. In this case, since magnetic force is qv X B, the magnetic force points up. This means that the mobile charges (positive) will be pushed towards the top of the block and the negative charge will be at the bottom of the block, so that the block will remain neutrally charged. Remember: a voltmeter will have a positive reading if the positive end is connected to the part with the larger potential. In this case, the larger potential is at the top because that is where the positive charge is, but the negative end of the voltmeter is connected there. The voltmeter will have a negative reading.
===Middling===

Question: A battery and metal block are connected by 2 wires. Conventional current flows counterclockwise. A voltmeter is attached to the block with its positive lead at the top of the block and its negative lead at the bottom of the block. The voltmeter has a positive reading. What sign does the mobile charge have? (See attached diagram)

[[File:image2.jpg]]

Answer: First of all, due to the Voltmeter having a positive reading, we know that the electric field perpendicular (or the electric field that the Voltmeter is telling us about) points from where the positive lead of the voltmeter is connected to the negative lead (in this example, from top to bottom). We also know that Fmagnetic + Felectric_perpendicular equals zero, so F_b and F_e must have opposite signs. F_b is calculated using I*dl X B. The right hand rule tells us that F_b points in the positive y direction. This tells us that F_e perpendicular must point in the negative y direction. F_e is simply (E*q). As determined earlier, E already points in - y direction so we can conclude that the mobile charges are positive.

===Difficult===

Question: A battery and metal block are connected by two wires. There is also a magnetic field coming out of the page. You are told that the Efield perpendicular is point in the positive y direction. There is also a voltmeter with the positive lead on the top of the block and the negative lead is on the bottom of the block. You are asked to find: the sign of the potential difference that the voltmeter will measure, the polarization of the block, and the sign of the mobile charge. (See attached diagram)

[[File:PhotoC.jpg]]

===Important Tricks===

Hall effect can only be tested so many ways. There are a few tricks to keep in mind.

[[File:HALL1.png]]

for example look at the photo above. There a Voltmeter connected to a sheet of metal. SInce the voltmeter reads a negative voltage, you can automatically assume that the side connected to the negative terminal of the voltmeter is connected to the positive side of the metal due to hall effect. This is because that a voltmeter is reading a charge in the opposite direction.

[[File:HALL2.png]]

You can try this in lab as well. Use a voltmeter and measure the voltage across a battery, if you switch between the positive and negative sides, then you also which between a positive and negative values. If the value is negative, then you are going in the opposite direction of the current.

CASE 2:

You have a conductive metal passing a wire with a voltage the blue X's are a magnetic field going into the page.
[[File:HALL4.png]]
Current of the Box is moving from the right to the left though the middle of the box, and as you can see from the voltameter, the siders are negative and positive polarized as listed in the picture. The negative voltage is due to the defection of electrons to the sensors in the voltameters.

Equilibrium is met in a problem with electric force is equal to a magnetic force, in this example, the electric field is from the polarized conductor.

So if Eh is the electric field from the hall effect,
then the following is true of the system above in Equilibrium.
Fe=Fb
q*Eh=q*v*B
so
Eh=v*B

Where v is the velocity of the block entering the square wire
Vh=(Voltage read on voltmeter)

Also note that if d is the width of the conductor, then the hall voltage Vh measured by the voltmeter is:

Vh=Eh*d=v*B*d

In this case, because F_b is (I*dl) X B, we can say that F_b points in the negative y direction. Since F_b must equal -F_e, F_e must point in the + y direction. E perpendicular does, so this means that our mobile charge is positive (See the previous problem for more explanation of finding the mobile charge). The polarization is determined by analyzing which way the magnetic force (before the Electric force cancels it out) pushes the mobile charge. In this case, the magnetic force pushes the positive mobile charge to the bottom, so negative mobile charges are at the bottom of the block to maintain neutrality. If the positive lead is connected to the place of higher potential (the positive polarization of the block), then the volt meter would read positive. In this case, the positive lead is connected to the place of lower potential, so the voltmeter would be negative.

==Connectedness==
How is this topic connected to something that you are interested in?

I really enjoy puzzles and I feel as though the Hall Effect is pretty much a large puzzle. You are given a little bit of information and also have several key physics laws and from that you can figure out a lot about a piece of metal.

How is it connected to your major?

Hall effect is all about seeing the relationship between magnetic and electric forces while also remembering how metals polarize. This means that it has a lot of mechanical and machine applications. It can sense when a magnetic field or electric field changes, so it can control many machines, apply pressures, and report many values. All of these skills are very important for Mechanical Engineering, so this topic has a lot of relevence to my major. Also, a lot engineering in general is about analyzing concepts before calculating a lot of values. The idea of the Hall Effect gives a lot of important data without the use of any numbers (of course it gives more info with the calculation of numbers). This reasoning process required for the Hall Effect is a very helpful skill for engineers to have.

Is there an interesting industrial application?

Hall Effects are used in industry to aid in the control of Hydraulic systems such as moving cranes and backhoes. It is also used to help sense a car wheel's motion to aid in the use of anti-skid/anti-lock brakes.

===Explore its application in a lab setting??===

Hall effect is also taken into consideration when hall probes are used as magnetometers.

A Hall probe is used to measure the difference of magnetic flux perpendicular to its sensor. this information is then fed to a magnetometers to help read the difference in magnetic fields.

This is a link to buys a hall effect sensor. if you would ever want to buy one!
http://www.ebay.com/sch/i.html?_nkw=hall+effect+sensor

and here is where you can buy a magnetometer
http://www.ebay.com/itm/EM2-EARTH-MAGNETOMETER-MAP-MAGNETIC-FIELDS-SURVEY-TOOL-/251324557405?hash=item3a841c685d:m:m8gnViuidubx7vMbMejiNNA

To use this idea in a lab, simply create circuit through a conductive material, like a piece of foil, and calculate the direction of the magnetic field using right hand rule. Use this information to
to then properly add the hall probes to the foil so they are perpendicular to the magnetic field, and then BOOM! You will have information to read to a magnetometer.

==History==
[[File:HALL3.jpg]]

The Hall Effect was discovered in 1879 by Edwin Herbert Hall while he was attending Johns Hopkins University for his Doctoral Degree. He exposed a gold leaf (metal slab) to a magnetic field perpendicular to its surface and had current flow through the slab. He observed a potential (delta V) perpendicular to the current and also the magnetic field. This means that potential is observed not only in the direction of current flow like usual. This is what led to Hall's discovery o the Hall Effect.

===CONCLUSION: IF YOU WANT TO REMEMBER ANYTHING, THIS IS IT===
1. When a current carrying metal/conductor is placed in a magnetic field, a voltage is formed perpendicular to both current and magnetic field

2. The Hall effect is made when the charges create almost a polarized metal, as a result the conductor experience charge carriers

3. Right hand rule whenever in doubt.
== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

[[Combining Electric and Magnetic Forces]]

[[Biot-Savart Law for Currents]]

[[Lorentz Force]]
===Further reading===

Books, Articles or other print media on this topic

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

http://www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf

===External links===

Internet resources on this topic

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/hall.html

https://www.youtube.com/watch?v=_ATDraCQtpQ

==References==

This section contains the the references you used while writing this page

https://en.wikipedia.org/wiki/Hall_effect

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/press.html

https://en.wikipedia.org/wiki/Edwin_Hall

Matter and Interactions: Volume 2 by Ruth Chabay and Bruce Sherwood (4th Edition)

[[Category:Which Category did you place this in?]]

Hall Effect

2017-12-02T05:36:32Z

Seprudencio: /* Explore its application in a lab setting?? */

Elastic Collisions

2017-12-01T22:57:10Z

Seprudencio: /* History */

==The Main Idea==

So what exactly is an elastic collision? You may be thinking of bubble gum or rubber bands, but "elastic" actually refers to the change in internal energy in the collision. An elastic collision does not have any change in the internal energy of the bodies involved.

First, we need to define a collision. A collision is an event/process in which two objects interact strongly for a short amount of time and in which there was very little interaction before they interacted and after the interaction. An elastic collision is a collision between two or more objects in which there is no loss in kinetic energy before and after the collision. If we assume that the colliding objects are part of the system and that there is no force from the surroundings, the final kinetic energy is still in the same form as it was initially. This is because the surrounding forces are considered to have a negligible impact compared to the forces that occur between the colliding objects. To keep it simple, this means that kinetic energy in = kinetic energy out. Usually, you can determine if a collision is elastic or not by seeing if the objects bounce off one another, which is not the case in inelastic collisions. To find the difference between the two types of collisions, keep in mind that momentum is transferred in both collisions, which means that the best way of differentiating would be to look at the transfer of kinetic energy. If the difference of internal and kinetic energy is equal to zero, then the collision is elastic. Apart from looking to see if the objects bounce off another or not, we can also judge by looking to see if the objects get deformed, are hotter, have more vibration/rotation or are in an excited state after collision. If any of the above happens, the collision is '''not''' elastic.

[[File:Elastischer_stoß2.gif|350px|thumb|right]]

Additionally, elastic collisions are a wonderful representation of the conservation of momentum which states that the momentum of an isolated system is constant. For an isolated system undergoing an elastic collision momentum in = momentum out.

Pool is a great real-world example of elastic collisions. The game provides a great way to observe close to ideal elastic collision conditions in everyday life.

[[File: boing.gif|350px|thumb|right]]

It's important to note that with macroscopic systems there are no perfectly elastic collisions because there's always some dissipation (for example thermal energy emitted), but most are nearly elastic. The only time there are perfect collisions is on a microscopic level when atomic systems with quantized energy collide, but that's only if there is enough energy available to raise the systems to an excited quantum state—but quantum energy is really a whole other topic. Let's focus on elastic collisions!

Here's a video walkthrough of a basic elastic collision: https://www.youtube.com/watch?v=V4vzNk4qppw

===A Mathematical Model===

Now lets take what we know about elastic collisions and talk about it in mathematical terms. There are three main mathematical concepts surrounding elastic collisions:

1. <math> K_f = K_i </math>

2. <math> \Delta E_{int} = 0 </math>

<math> \Delta E_{sys} + \Delta E_{surr} = 0 \\</math>
<math> \Delta E_{surr} = 0 </math> , so <math> \Delta E_{sys} = 0 </math>
<math> E_{final} = E_{initial} \\</math>

3. <math> \vec{p}_f = \vec{p}_i </math>

<math> \Delta \vec{p}_{sys} + \Delta \vec{p}_{surr} = 0 \\</math>
<math> \Delta \vec{p}_{surr} = 0 </math> , so <math> \Delta \vec{p}_{sys} = 0 </math>
<math> \vec{p}_{final} = \vec{p}_{initial} \\</math>

===Example Problem===

[[File:Example1good.jpg|300px|thumb|right]]

Cart 1, moving in the positive x direction, collides with cart 2 moving in the negative x direction. Both carts have identical masses and the collisions is (nearly) elastic, as it would be if the carts interacted magnetically or repelled each other through soft springs. What are the final momenta of the two carts?

1. After choosing a correct system, surroundings, and initial and final states, we can apply the momentum principle mentioned above to get a relationship
between the initial and final momentums of the two carts. Usually, when we want to consider the system, we will consider the two colliding objects as the system and the rest as the surroundings. The initial state would be before the collision, and the final state would be after.

Momentum Principle: <math> \vec{p}_{final} = \vec{p}_{initial} + \vec{F}_{net}\Delta t </math>

And it turns into: <math> \vec{p}_{1f} + \vec{p}_{2f} = \vec{p}_{1i} + \vec{p}_{1f} </math> since during the collision, the <math> F_{net} </math> is negligible.

2. Next, by applying the energy principle we can gain knowledge about the final and initial kinetic energies. By acknowledging the fact that the change in internal energy is 0 and the fact the reaction happens so quickly that not work or heat transfer is done by the surroundings, the equation can be simplified to include just initial and final kinetic energies.

The Energy Principle: <math> \Delta E_{sys} = W + Q </math>

We then get rid of the work, heat transfer and internal energies:

<math> K_{1f} + \Delta E_{1int} + K_{2f} + \Delta E_{2int} = K_{1i} + K_{2i} + W + Q \\ </math>
<math> \Delta E_{1int} = \Delta E_{2int} = W = Q = 0 \\ </math>
<math> K_{1f} + K_{2f} = K_{1i} + K_{2i} </math>

The reason the internal energies are directly crossed out is because we can put them to one side since <math> E_{final} = E_{initial} </math> and therefore <math> E_{final} -
E_{initial} = 0 </math>.

3. Once we have simplified the momentum and energy principles, one can use the relationship between kinetic energy and momentum mentioned above to get a relationship involving both energy and momentum. Once this is obtained, the equation can be shifted around to get both the final momentums.

Kinetic Energy Definition: <math> K = \frac{p^2}{2m} </math>

Finished Result: <math> \frac{p^2_{1f}}{2m} + \frac{p^2_{2f}}{2m} = \frac{p^2_{1i}}{2m} + \frac{p^2_{2i}}{2m} </math>

===Computational Models===

The trinket model linked demonstrates an elastic collision between two spheres.

[https://trinket.io/glowscript/f3bc1dd31f Elastic Collision Glowscript Model]

The video below demonstrates a basic car crash elastic collision using MATLAB. Take note of the changes in displacement and the time.

[https://www.youtube.com/watch?v=AfCfCS6O2VM Elastic Collision MATLAB model]

==Examples==

===Reminders===

Be sure to show all steps in your solution and include diagrams whenever possible. For a lot of the complicated problems, starting with a diagram and writing down the given information and plugging that into either the momentum or energy principle can help you move forward in the problem. It would be better to also write the main principles at the side to remind yourself of how you found it. If you still get stuck, try finding similar examples to that problem and look at the solutions to get on the right track.

===Simple===

Let’s start with a simple example like the ones you don't see on the test.

Jay and Sarah are best friends. Since they’re best friends they both weigh <math> 55 kg </math>. Jay hadn’t seen Sarah in a long time so when she saw her she ran to her with a velocity of <math><4,0,0> m/s</math>. Instead of a hug, they were both too excited and collided and bounced back off of each other, and Sarah flew back with a velocity of <math><7,0,0> m/s</math>. What was Jay’s final velocity?

[[File:Problem1.0.png|300px|Problem 1]]

In a lot of simple elastic collision problems, the momentum principle is all you need to solve them. Most problems will the initial velocities, masses, and one final velocity and you will be asked to solve for a either a final velocity or final momentum. By setting up an equation like the one in this problem, one can easily handle this type of problem.

===Middling===

When far apart, the momentum of a proton is <math><5.2 * 10^{−21}, 0, 0> kg · m/s</math> as it approaches another proton that is initially at rest. The two protons repel each other electrically, but they are not close enough to touch. When they are far apart again later, one of the protons now has a velocity of <math><1.75, .82, 0> m/s</math>. At that instant, what is the momentum of the other proton? HINT: The mass of a proton is <math>1.7 *10^{-21} kg</math>.

[[File:Problem2.0.png|300px]]

A lot of people freak out when they see problems involving atomic particles and electrical forces, but the concept is the same no matter the scale. For this problem we are given masses, velocities, and momentum, but the equation <math>p = mv</math> allows us to easily handle these different values. Once again drawing a diagram helps to understand what is actually happening in the problem, making it easier to put the values in the correct places and solve.

===Difficult===

Okay, let's get a little bit trickier here...

There is a <math>400 kg</math> train traveling at <math>55 m/s</math> that collides, elastically of course, with a random <math>2 kg</math> trashcan that's stationary on the tracks. Afterwards, what are the speeds of both the train and the trashcan after the collision?

[[File:Problem3.0.png|400px]]

This was a difficult problem because of the assumptions we had to make in order to solve it. Because the collision was elastic we were able to disregard the change in internal energy in the energy principle, and since it happened so quickly the work done by the track and heat transfer between the surroundings was negligible. It is tough to tell what assumptions you can make and which ones you can't in problems like these, which is what can make them difficult. On most exams or quizzes the collision problems will be inelastic simply because they are harder, but it is important to understand the fundementals of elastic collisions and how to solve problems involving them.

==Connectedness==

So how are collisions connected to the real world? Collisions are all around us!

One main example is cars. Lots of car companies will purposely test and wreck cars to test collisions! Data is then sent to places like the Insurance Institute for Highway Safety where we can learn about car agility and more.

[[File:IIHS_Hyundai_Tucson_crash_test.jpg|500px]]

Another example of collisions in real life is billiards. This is one of the most accurate real life examples of elastic collisions. One ball hits another ball at rest, and if done right the first ball stops and transfers nearly all its kinetic energy into kinetic energy in the second ball. We consider this a head on collision of equal masses.

[[File:Billiards_and_snookers.jpg|500px]]

A third example is hitting a baseball. Hitting a ball off the end or to close the hands of a bat will cause some vibrational energy from the collision, but if the ball catches the sweet spot the collision is very elastic, and you don't feel any vibration when you strike the ball.

[[File:Marcus_Thames_Tigers_2007.jpg|500px]]

Elastic collisions also happen between particles. The Rutherford Scattering experiment mentioned below is a good example.

==History==

Collisions are certainly not a new concept in the world. Ever since the beginning or time things have been colliding and reacting in different ways. It was experiments done by scientists like Newton or Rutherford that started to characterize collisions into categories and apply fundamental principles of physics to the reactions. What we observed above was the Newtonian way.

The history of collisions originates from the Rutherford Scattering experiment. It consisted of shooting alpha particles through a thin gold foil. As Rutherford studied the scattering of alpha particles through metal foils, he first noticed a collision with a single massive positive particle. Although the alpha particles did not hit the nucleus of the gold atoms, they did interact with each other and therefore can be considered as a collision. Since the interaction did not excite the gold atoms, fortunately enough, it was an elastic collision. This lead to the conclusion that the positive charge of the mass was concentrated in the center, the atomic nucleus! The plum pudding model (where the positive and negative charges were stuck within the atom like plums in a pudding), that had been around was disproved. When further research was done, they measured the angle of the 'scattering' or the particles shot through a tin gold foil. Had the collisions been inelastic, the particles would not have been able to bounce back.

[[File:gold-foil-experiment.jpg]]

Here is a youtube clip detailing the experiment: [https://www.youtube.com/watch?v=5pZj0u_XMbc Rutherford Scattering Experiment]

== See also ==

http://physicsbook.gatech.edu/Collisions for a general understanding of all collisions.

http://physicsbook.gatech.edu/inelastic_collisions to contrast them from elastic collisions.

===Further reading===

http://www.britannica.com/science/elastic-collision

===External links===

[http://www.physicsclassroom.com/mmedia/momentum/trece.cfm Elastic Collision Example]

[http://hyperphysics.phy-astr.gsu.edu/hbase/elacol2.html Different Types of Elastic Collisions]

[https://www.boundless.com/physics/textbooks/boundless-physics-textbook/linear-momentum-and-collisions-7/collisions-70/elastic-collisions-in-one-dimension-298-6220/ A Lesson on Collisions]

==References==

Main Idea:

''Matter and Interactions, 4th Edition''

http://www.sparknotes.com/testprep/books/sat2/physics/chapter9section4.rhtml

http://blogs.bu.edu/ggarber/archive/bua-physics/collisions-and-conservation-of-momentum/

History:

''Matter and Interactions, 4th Edition''

https://en.wikipedia.org/wiki/Elastic_collision

https://www.youtube.com/watch?v=5pZj0u_XMbc

Connectedness:

http://www.iihs.org/

Additionally used references from ''see also''.