2049_ch30B - Direction of Induced Current Bar magnet moves...

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PHY2049: Chapter 30 16 Bar magnet moves through coil ¾ Current induced in coil Reverse pole ¾ Induced current changes sign Coil moves past fixed bar magnet ¾ Current induced in coil as in (A) Bar magnet stationary inside coil ¾ No current induced in coil Direction of Induced Current S N v S N v N S S N A B C D v
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PHY2049: Chapter 30 17 ConcepTest: Lenz’s Law Î If a North pole moves towards the loop from above the page, in what direction is the induced current? ± (a) clockwise ± (b) counter-clockwise ± (c) no induced current Must counter flux change in downward direction with upward B field
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PHY2049: Chapter 30 18 ConcepTest: Induced Currents Î A wire loop is being pulled through a uniform magnetic field. What is the direction of the induced current? ± (a) clockwise ± (b) counter-clockwise ± (c) no induced current x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x No change in flux, no induced current
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PHY2049: Chapter 30 19 ConcepTest: Induced Currents In each of the 3 cases above, what is the direction of the induced current? (Magnetic field is into the page and has no boundaries) (a) clockwise (b) counter-clockwise (c) no induced current x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x 1 2 3 Counter None None (max flux, so not changing)
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PHY2049: Chapter 30 20 ConcepTest: Lenz’s Law Î If a coil is shrinking in a B field pointing into the page, in what direction is the induced current? ± (a) clockwise ± (b) counter-clockwise ± (c) no induced current Downward flux is decreasing, so need to create downward B field
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PHY2049: Chapter 30 21 Induced currents Î A circular loop in the plane of the paper lies in a 3.0 T magnetic field pointing into the paper. The loop’s diameter changes from 100 cm to 60 cm in 0.5 s ± What is the magnitude of the average induced emf?
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This note was uploaded on 04/12/2008 for the course PHY 2049 taught by Professor Any during the Fall '08 term at University of Florida.

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2049_ch30B - Direction of Induced Current Bar magnet moves...

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