29_Lec-16

# 29_Lec-16 - Physics 241 Lecture 16 Y E Kim Chapter 28...

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Physics 241 Lecture 16 Y. E. Kim October 21, 2010 Chapter 28, Sections 1 ² 3 October 22, 2010 University Physics, Chapter 23 1

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Electromagnetic Induction ± )DUDGD\·V ([SHULPHQWV ± )DUDGD\·V /DZ ± /HQ]·V /DZ October 22, 2010 2
October 22, 2010 University Physics, Chapter 29 3 )DUDGD\·V ([SHULPHQWV ±²³ ± When we move the north pole of the magnet toward the wire loop, we induce a positive current in the loop ± When we move the south pole of the magnet toward the loop, we induce a negative current in the loop

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October 22, 2010 University Physics, Chapter 29 4 )DUDGD\·V ([SHULPHQWV ±²³ ± 1RZ OHW·V SRLQW WKH QRUWK SROH WRZDUG WKH ORRS EXW move away from the loop ± We get a negative current ± We turn the magnet around so that the south pole points toward the loop and move away from the loop ± We get a positive current
October 22, 2010 University Physics, Chapter 29 5 )DUDGD\·V ([SHULPHQWV ±²³ ± We can create similar effects by placing a second loop near the first loop ± If a constant current is flowing through loop 1, no current will be induced in loop 2 ± If we increase the current inloop 1, we observe that a current is induced inloop 2 in the opposite direction

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October 22, 2010 University Physics, Chapter 29 6 )DUDGD\·V ([SHULPHQWV ±²³ ± Now if we have the current flowing in loop 1 in the same direction as before, and decrease the current as indicated below, we induce a current in loop 2, in the same direction as the current in loop 1
October 22, 2010 University Physics, Chapter 29 7 )DUDGD\·V /DZ RI ,QGXFWLRQ ± From these observations we see that a changing magnetic field induces a current in a loop ± We can visualize the change in magnetic field as a change in the number of magnetic field lines passing through the loop ± )DUDGD\·V /DZ RI ,QGXFWLRQ states that: ± An emf is induced in a loop when the number of magnetic field lines passing through the loop changes with time ± The rate of change of magnetic field lines determines the induced emf

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Physics 241 ² 29 ² QUIZ 1 ² October 21, 2010 The four figures show a bar magnet and a low voltage light bulb connected to the ends of a conducting loop. The plane of the loop is perpendicular to the dotted line. In case 1 , the loop is stationary, and the magnet is moving away from the loop. In case 2 , the magnet is stationary, and the loop is moving toward the magnet. In case 3, both the magnet and loop are stationary, but the area of the loop is increasing. In case 4,
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## This note was uploaded on 09/09/2011 for the course PHYS 241 taught by Professor Wei during the Fall '08 term at Purdue.

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29_Lec-16 - Physics 241 Lecture 16 Y E Kim Chapter 28...

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