quiz_solutions07

Fundamentals of Physics, (Chapters 21- 44) (Volume 2)

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PY212 Solutions Quiz 7 (a) There is a current because of the emf and the resistance: R i / ε = (this is Ohm’s law). The emf is produced by a change in flux which is produced by a change in area (see also Eq. 30-8): V, 14 . 0 ) m/s 25 )( m 10 0 . 8 )( T 10 70 ( ) ( ) ( ) 1 ( 2 3 = × × = = = = = Φ = BLv dt dx BL dt Lx d B dt BA d dt d N such that mA. 8 . 2 ) 50 /( ) V 14 . 0 ( / = Ω = = R i (b) There are two ways to find the direction of the current (both using Lenz’s law): “Nature is working against us”; it produces a force opposite to our force. We are pulling the rod to the right, so the induced force (which is caused by the induced current) is to the left. The right-hand rule tells us that the current must be going up (because B is into the page and the induced force is to the left). “Nature tries to fix the magnetic flux.” In this case the flux is becoming smaller, so Nature induces a magnetic field B ind to try to fix the flux. We are making the flux smaller, so Nature tries to make it larger; in other words
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This document was uploaded on 07/10/2009.

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