Direction of Magnetic Field - Revision history

Dlong42 at 01:14, 6 December 2015

2015-12-06T01:14:07Z

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 Recall that the equation for magnetic field due to a moving charged particle is <math> \vec{B}  =\frac{\mu_0}{4\pi} \frac{(q\vec{v} \times \hat{r})}{|\vec{r}|^2}  </math>, otherwise known as the good-ole Biot-Savart law. The most important thing to note about this in regards to direction of magnetic field is that this is a '''cross product''' between the charge of the moving particle times its velocity, <math> q\vec{v} </math> and the unit distance vector from the particle to the observation location, <math> \hat{r} </math>. This Biot-Savart law is the basis for every orientation of magnetic field you will encounter in this class (wires, magnetic dipoles, etc), and its cross product is what makes finding the direction of magnetic field much trickier than finding the direction of electric field.
-Physics professors and problem makers will put wires in various shapes and orientations to try and confuse you, but as long as you stick to what you know, and
+===A Computational Model===
 ==Important Scenarios==
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 At point B, both the magnetic field of the top wire and the bottom wire point out of the page and combine, causing the net magnetic field at point B to point out of the page. At point A, the top wire's magnetic field points into the page, and the bottom wire's magnetic field points out of the page. However, magnetic field decreases as distance increases, so the net field at point A points into the page, the direction of the closest wire's field. Point C has the same explanation as point A, with the bottom wire's field greater than the top wire's.
 ===A Coil of Wire===

Dlong42 at 00:46, 6 December 2015

2015-12-06T00:46:42Z

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	==References==		==References==

	~~This section contains the the references you used while writing this page~~		===Photo Creds===

	Page initiated by --[[User:Dlong42\|Dlong42]] ([[User talk:Dlong42\|talk]]) 23 October 2015		https://commons.wikimedia.org/wiki/File:Right_hand_rule_cross_product.svg

			http://viz.aset.psu.edu/gho/sem_notes/3d_fundamentals/html/3d_coordinates.html

			https://en.wikipedia.org/wiki/Jean-Baptiste_Biot

			==Author==
			Page initiated by Devon Long--[[User:Dlong42\|Dlong42]] ([[User talk:Dlong42\|talk]]) 23 October 2015

	[[Category:Fields]]		[[Category:Fields]]

Dlong42 at 00:41, 6 December 2015

2015-12-06T00:41:41Z

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	==Connectedness==		==Connectedness==
	#How is this topic connected to something that you are interested in?		*How is this topic connected to something that you are interested in?
	#How is it connected to your major?		**I personally find problems like these kind of fun, that require you to visualize and use things that you know to figure something else out. Also, I've always been interested in the things that go on in our universe that we can't see, so observing the ways that magnetic fields behave is super interesting.
	#Is there an interesting industrial application?		*How is it connected to your major?
			**As a mechanical engineer, lots of the same principles used for magnetic fields come up in engineering classes as well. The right hand rule can be used for lots of different physical properties based on cross products, such as moments and torque.
			*Is there an interesting industrial application?
			**Magnetic field are used in so many products and processes, it would take an extensive amount of time to put together a list. Relevant ones to our lives are our computers we do homework on and our smart phones that we use every day!

	==History==		==History==
			[[File:Jean baptiste biot.jpg\|thumb\|Jean-Baptiste Biot]]
			The 19th century was pretty much the golden age of major discoveries on the basics of magnetic fields. The Biot-Savart Law, which this wiki page is technically based on, was derived after a series of experiments by French scientists Jean-Baptiste Biot and Félix Savart in the year 1820.

	~~Put this idea in historical context. Give the reader the Who, What, When, Where, and Why.~~		== See also ==

			[[Magnetic Field]]

			[[Right-Hand Rule]]

	~~== See also ==~~		[[Magnetic Field of a Long Straight Wire]]

			[[Magnetic Field of a Loop]]

			[[Magnetic Field of a Solenoid]]

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

	===External links===		===External links===

	~~Internet resources~~ on ~~this topic~~		====Resource for right hand rule====
			http://physicsed.buffalostate.edu/SeatExpts/resource/rhr/rhr.htm

			====Encyclopaedia Britannica Entry on Biot-Savart Law====
			http://www.britannica.com/science/Biot-Savart-law

	==References==		==References==

Dlong42 at 00:16, 6 December 2015

2015-12-06T00:16:58Z

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	Notice that similar to an electric dipole, the magnitude of the magnetic field is larger at the ends of the bar magnet than at the sides.		Notice that similar to an electric dipole, the magnitude of the magnetic field is larger at the ends of the bar magnet than at the sides.

			===Coils As Magnetic Dipoles===

			As it turns out, when viewed from a far enough distance, a current-carrying coil shows features of a magnetic dipole. The only difference between the coil and the bar magnet is that the coil doesn't have a predetermined north or south pole. The direction of current determines that instead, meaning you must use the right hand rule to discover which way the field orients.

			Here's a final visual to show you what it looks like. Note that current in this coil is flowing counter-clockwise if you look down towards the top of the coil.

			[[File:Coildipole.jpg\|300px]]

	==Connectedness==		==Connectedness==

Dlong42 at 00:06, 6 December 2015

2015-12-06T00:06:37Z

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	Here's a comparison to help you visualize this phenomenon:		Here's a comparison to help you visualize this phenomenon:

	[[File:DipoleComparison.jpg]]		[[File:DipoleComparison.jpg\|300px]]

			Now that you're familiar with the pattern, try an example.

			====Example====

			In what direction is the magnetic field at points A, B, C, and D?

			[[File:Barmagprob.jpg\|300px]]

			Your answer should be based on the dipole pattern you are familiar with:

			[[File:Barmagsol.jpg\|300px]]

			Notice that similar to an electric dipole, the magnitude of the magnetic field is larger at the ends of the bar magnet than at the sides.

	==Connectedness==		==Connectedness==

Dlong42 at 23:56, 5 December 2015

2015-12-05T23:56:51Z

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	====Bar Magnet====		====Bar Magnet====

	One of the simplest magnetic dipoles is a bar magnet. A bar magnet is composed of a small "bar" with a north side and a south side. A bar magnet works exactly the same way an electric dipole does in regards to the direction of field created by it. The important concept to remember is that the north ~~end~~ of the bar magnet corresponds to the positive end of the electric dipole, and the south ~~end~~ of the bar magnet corresponds to the negative end of the electric dipole.		One of the simplest magnetic dipoles is a bar magnet. A bar magnet is composed of a small "bar" with a north side and a south side. A bar magnet works exactly the same way an electric dipole does in regards to the direction of field created by it. The important concept to remember is that the north "pole" of the bar magnet corresponds to the positive end of the electric dipole, and the south "pole" of the bar magnet corresponds to the negative end of the electric dipole.

			Here's a comparison to help you visualize this phenomenon:

			[[File:DipoleComparison.jpg]]

Dlong42 at 23:48, 5 December 2015

2015-12-05T23:48:08Z

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	Remember electric dipoles? Of course you do. Put a positive and negative charge together and you get a really fancy pattern of electric field, where the field comes out of the positive side of the dipole, curls around, and goes back into the negative side. Luckily for you, magnetic dipoles are super easy, because they use the '''exact same pattern'''.		Remember electric dipoles? Of course you do. Put a positive and negative charge together and you get a really fancy pattern of electric field, where the field comes out of the positive side of the dipole, curls around, and goes back into the negative side. Luckily for you, magnetic dipoles are super easy, because they use the '''exact same pattern'''.

			====Bar Magnet====

			One of the simplest magnetic dipoles is a bar magnet. A bar magnet is composed of a small "bar" with a north side and a south side. A bar magnet works exactly the same way an electric dipole does in regards to the direction of field created by it. The important concept to remember is that the north end of the bar magnet corresponds to the positive end of the electric dipole, and the south end of the bar magnet corresponds to the negative end of the electric dipole.

Dlong42 at 22:36, 5 December 2015

2015-12-05T22:36:57Z

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	[[File:Coilsol.jpg\|300px]]		[[File:Coilsol.jpg\|300px]]

			Use both right hand rules yourself and discover how both of them lead you to the same answer. Coils will come up more frequently as this class goes on, so make sure you remember how to find the direction of the magnetic field created by them.

			===Magnetic Dipoles===

			Remember electric dipoles? Of course you do. Put a positive and negative charge together and you get a really fancy pattern of electric field, where the field comes out of the positive side of the dipole, curls around, and goes back into the negative side. Luckily for you, magnetic dipoles are super easy, because they use the '''exact same pattern'''.



	==Connectedness==		==Connectedness==

Dlong42 at 22:31, 5 December 2015

2015-12-05T22:31:00Z

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 ===A Coil of Wire===
 There is one special case for a current carrying wire you need to know: a circular coil of wire. [[File:Coilofwire.jpg|thumb|A coil with many turns.]]
 ==Connectedness==

Dlong42 at 22:14, 5 December 2015

2015-12-05T22:14:52Z

← Older revision		Revision as of 18:14, 5 December 2015
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	At point B, both the magnetic field of the top wire and the bottom wire point out of the page and combine, causing the net magnetic field at point B to point out of the page. At point A, the top wire's magnetic field points into the page, and the bottom wire's magnetic field points out of the page. However, magnetic field decreases as distance increases, so the net field at point A points into the page, the direction of the closest wire's field. Point C has the same explanation as point A, with the bottom wire's field greater than the top wire's.		At point B, both the magnetic field of the top wire and the bottom wire point out of the page and combine, causing the net magnetic field at point B to point out of the page. At point A, the top wire's magnetic field points into the page, and the bottom wire's magnetic field points out of the page. However, magnetic field decreases as distance increases, so the net field at point A points into the page, the direction of the closest wire's field. Point C has the same explanation as point A, with the bottom wire's field greater than the top wire's.

			===A Coil of Wire===
			There is one special case for a current carrying wire you need to know: a circular coil of wire. [[File:Coilofwire.jpg\|thumb\|A coil with many turns.]]

	==Connectedness==		==Connectedness==