ch20_review - A. Manalaysay PHY2054, Fall 2004 CHAPTER 20...

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A. Manalaysay – PHY2054, Fall 2004 CHAPTER 20 In this chapter we learn that a magnetic field that changes in time can produce an electric field. In particular, if we have a loop of wire, and the magnetic flux through the loop changes, a voltage is produced: --- Faraday’s Law : “N” is the number of turns in the loop, and “ is the magnetic flux: same definition as electric flux back in chapter 15, except you use B instead of E. Most of the time we are interested in the magnitude of the induced voltage, so we drop the negative sign. But it is important, because it reminds us what direction the induced current will flow. The negative sign is Lenz’s Law. Faraday’s Law tells us what the induced voltage is, Lenz’s Law tells us in what direction it will be. It says that the loop will do whatever it can to counteract the change in flux. Here’s my version of Lenz’s Law: Lenz’s Law in 3 easy steps: 1. Stick your [right] thumb in the direction of the applied magnetic field.
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This note was uploaded on 01/15/2012 for the course PHY 2054 taught by Professor Avery during the Spring '08 term at University of Florida.

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