Feedback: Difference between revisions

Latest revision as of 19:49, 5 December 2015

Written by Krishna Peri

Feedback is an integral part of circuits. Feedback occurs when the output of a system is routed back as a secondary input to the system. This way the overall output of the system depends on the previous outputs of the system. Feedback is creating a cause and effect chain where the output is both a cause and effect.

The effect of Feedback

Feedback is important in order to route the output of the loop back into the input, so that the overall output is affected by the previous outputs. In RC circuits, feedback allows current equalization and causes current to follow the wire. Feedback is a concept that you should know about circuits, however there are NO calculations that occur in regards to feedback. Feedback is not a major component of the circuits we use in Intro Physics, because it requires more complex circuits in order to be implemented. However, the concept is something you should be familiar with.

The basic model representing feedback is:

Feedback and Current Equalization

Feedback in simple circuits equalizes the incoming and outgoing current that is flowing through a wire. if more incoming current you get a buildup of electrons. This buildup of electrons will cause the incoming current to slow down and outgoing current to speed up. If the outgoing current is faster than incoming current, there will be a buildup of positive charge. This will cause the incoming current to speed up (in order to equalize the positive charge) and slow down the outgoing current. This process will occur until the outgoing and incoming current ( i= nAv) are exactly equal to each other.

Feedback causes current to follow the wire

As stated previously Feedback allows current throughout a wire to equalize, this concept is what allows it to follow along a wire. Think of a wire with a a turn in it, the electrons do not which way to move so they buildup on the bend of the wire. When the buildup occurs the incoming current slows down which in turn causes the outgoing current (through bend into rest of wire) to speed up. This feedback process continually occurs which is why the current will continually follow the direction of the wire.

Connectedness

Feedback is important for Electrical Engineering and Computer Engineering majors, because it is an integral part of many circuit systems. If you want to learn more about how feedback is used in complex circuity take a look at some of the links in further reading.

History

Feedback is a concept that has existed for practically ever, however it didn't have a name until the 1860s in the US. Previously people knew it was a concept due to self regulating mechanisms. The term feedback was coined by Nobel Laureate Karl Ferdinand Braun in the year 1909.

References

The Feedback wikipedia page - https://en.wikipedia.org/wiki/Feedback

our physics book - Matter and Interactions volume II.

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-claimed by Kperi6
+Written by Krishna Peri
-Template
-Contents [hide]
-Thermodynamics
-.1 Zeroth Law
-.1.1 A Mathematical Model
-.1.2 A Computational Model
-.2 First Law
-.2.1 A Mathematical Model
-Second Law
-.1 Mathematical Models
-.2 Examples
-Connectedness
-History
-See also
-.1 Further reading
-.2 External links
-References
-Thermodynamics[edit]
-This topics focuses on energy work of a system but it can only deal with a large scale response to heat in a system. Thermodynamics is the study of the work, heat and energy of a system. The smaller scale gas interactions can explained using the kinetic theory of gases. There are three fundamental laws that go along with the topic of thermodynamics. They are the zeroth law, the first law, and the second law. These laws help us understand predict the the operation of the physical system. In order to understand the laws, you must first understand thermal equilibrium. Thermal equilibrium is reached when a object that is at a higher temperature is in contact with an object that is at a lower temperature and the first object transfers heat to the latter object until they approach the same temperature and maintain that temperature constantly. It is also important to note that any thermodynamic system in thermal equilibrium possesses internal energy.
-Zeroth Law[edit]
+Feedback is an integral part of  circuits.  Feedback occurs when the output of a system is routed back as a secondary input to the system. This way the overall output of the system depends on the previous outputs of the system. Feedback is creating a cause and effect chain where the output is both a cause and effect.
-The zeroth law states that if two systems are at thermal equilibrium at the same time as a third system, then all of the systems are at equilibrium with each other. If systems A and C are in thermal equilibrium with B, then system A and C are also in thermal equilibrium with each other. There are underlying ideas of heat that are also important. The most prominent one is that all heat is of the same kind. As long as the systems are at thermal equilibrium, every unit of internal energy that passes from one system to the other is balanced by the same amount of energy passing back. This also applies when the two systems or objects have different atomic masses or material.
-A Mathematical Model[edit]
+==The effect of Feedback==
-If A = B and A = C, then B = C A = B = C
-A Computational Model[edit]
+Feedback is important in order to route the output of the loop back into the input, so that the overall output is affected by the previous outputs. In RC circuits, feedback allows current equalization and causes current to follow the wire.  Feedback is a concept that you should know about circuits, however there are '''NO calculations that occur in regards to feedback.'''
-How do we visualize or predict using this topic. Consider embedding some vpython code here Teach hands-on with GlowScript
+Feedback is not a major component of the circuits we use in Intro Physics, because it requires more complex circuits in order to be implemented. However, the concept is something you should be familiar with.
-First Law[edit]
+The basic model representing feedback is:
-The first law of thermodynamics defines the internal energy (E) as equal to the difference between heat transfer (Q) into a system and work (W) done by the system. Heat removed from a system would be given a negative sign and heat applied to the system would be given a positive sign. Internal energy can be converted into other types of energy because it acts like potential energy. Heat and work, however, cannot be stored or conserved independently because they depend on the process. This allows for many different possible states of a system to exist. There can be a process known as the adiabatic process in which there is no heat transfer. This occurs when a system is full insulated from the outside environment. The implementation of this law also brings about another useful state variable, enthalpy.
+[[File:General_Feedback_Loop.svg|275px|thumb|center|''The Output is routed back as a second input'']]
-A Mathematical Model[edit]
+===Feedback and Current Equalization===
-E2 - E1 = Q - W
-Second Law[edit]
+Feedback in simple circuits equalizes the incoming and outgoing current that is flowing through a wire.  if more incoming current you get a buildup of electrons. This buildup of electrons will cause the incoming current to slow down and outgoing current to speed up.
-The second law states that there is another useful variable of heat, entropy (S). Entropy can be described as the disorder or chaos of a system, but in physics, we will just refer to it as another variable like enthalpy or temperature. For any given physical process, the combined entropy of a system and the environment remains a constant if the process can be reversed. The second law also states that if the physical process is irreversible, the combined entropy of the system and the environment must increase. Therefore, the final entropy must be greater than the initial entropy.
+If the outgoing current is faster than incoming current, there will be a buildup of positive charge. This will cause the incoming current to speed up (in order to equalize the positive charge) and slow down the outgoing current.
+This process will occur until the outgoing and incoming current ( i= nAv) are exactly equal to each other.
-Mathematical Models[edit]
+===Feedback causes current to follow the wire===
-delta S = delta Q/T Sf = Si (reversible process) Sf > Si (irreversible process)
-Examples[edit]
+As stated previously Feedback allows current throughout a wire to equalize, this concept is what allows it to follow along a wire.
-Reversible process: Ideally forcing a flow through a constricted pipe, where there are no boundary layers. As the flow moves through the constriction, the pressure, volume and temperature change, but they return to their normal values once they hit the downstream. This return to the variables' original values allows there to be no change in entropy. It is often known as an isentropic process.
+Think of a wire with a a turn in it, the electrons do not which way to move so they buildup on the bend of the wire. When the buildup occurs the incoming current slows down which in turn causes the outgoing current (through bend into rest of wire) to speed up. This feedback process continually occurs which is why the current will continually follow the direction of the wire.
-Irreversible process: When a hot object and cold object are put in contact with each other, eventually the heat from the hot object will transfer to the cold object and the two will reach the same temperature and stay constant at that temperature, reaching equilibrium. However, once those objects are separated, they will remain at that equilibrium temperature until something else acts upon it. The objects do not go back to their original temperatures so there is a change in entropy.
+==Connectedness==
+Feedback is important for Electrical Engineering and Computer Engineering majors, because it is an integral part of many circuit systems.  If you want to learn more about how feedback is used in complex circuity take a look at some of the links in further reading.
-Connectedness[edit]
+==History==
-How is this topic connected to something that you are interested in?
-How is it connected to your major?
-Is there an interesting industrial application?
-History[edit]
-Thermodynamics was brought up as a science in the 18th and 19th centuries. However, it was first brought up by Galilei, who introduced the concept of temperature and invented the first thermometer. G. Black first introduced the word 'thermodynamics'. Later, G. Wilke introduced another unit of measurement known as the calorie that measures heat. The idea of thermodynamics was brought up by Nicolas Leonard Sadi Carnot. He is often known as "the father of thermodynamics". It all began with the development of the steam engine during the Industrial Revolution. He devised an ideal cycle of operation. During his observations and experimentations, he had the incorrect notion that heat is conserved, however he was able to lay down theorems that led to the development of thermodynamics. In the 20th century, the science of thermodynamics became a conventional term and a basic division of physics. Thermodynamics dealt with the study of general properties of physical systems under equilibrium and the conditions necessary to obtain equilibrium.
-See also[edit]
+Feedback is a concept that has existed for practically ever, however it didn't have a name until the 1860s in the US. Previously people knew it was a concept due to self regulating mechanisms. The term feedback was coined by Nobel Laureate Karl Ferdinand Braun in the year 1909.
-Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?
-Further reading[edit]
-Books, Articles or other print media on this topic
-External links[edit]
+==Further reading==
-Internet resources on this topic
+Feedback, Nonlinear, and Distributed Circuits by Wai- Kai Chen
-References[edit]
+Designing Audio Power Amplifiers by Bob Cordell
-https://www.grc.nasa.gov/www/k-12/airplane/thermo0.html http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thereq.html https://www.grc.nasa.gov/www/k-12/airplane/thermo2.html http://www.phys.nthu.edu.tw/~thschang/notes/GP21.pdf http://www.eoearth.org/view/article/153532/
-Category: Which Category did you place this in?
+Circuit Analysis and Feedback Amplifier Theory by Wai - Kai Chen
+==References==
+The Feedback wikipedia page - https://en.wikipedia.org/wiki/Feedback
+our physics book - Matter and Interactions volume II.