Feedback

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.