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Unformatted text preview: t is the rate (in Joules/s = Watts) at which magnetic energy stored
in the inductor, L, is decreasing? 12 V L 2 mH 60 Ω 20 Ω
A)
B)
C)
D)
E)
1. calculate current in
inductor immediately
before the switch is
opened. 29 W
0W
48 W
7W
15 W This is the current that must
go through the two resistors
when the switch is opened.
Use it to calculate power. Version 1 Page 9 The rate that energy in
the inductor decreases is
equal to the power
dissipated in the two
resistors because that is
where the energy is
going. 16. Current I is charging a circular parallel plate capacitor with plate radius of R. The
circulation of the magnetic field, B dl , around a coaxial circular path between the
plates with r = R/3 has some definite value. Consider two surfaces bounded by this
circular path; the round flat surface (shaded); and the open soupcan (dashed). What can
we conclude from the AmpereMaxwell Law?
The total current of all kinds flowing in to the cylinder must be
exactly equal to the total current of all kinds flowing out. (this is a
paraphrase of the Kirchhoff junction rule). I The cylinder only covers 1/9 of the area of the capacitor plate. This
means only 1/9 of the displacement current of the capacitor goes
through the shaded side. To make up the difference 8/9 of current
must go out the sides in the form of conduction current (remember,
the charge has to spread out across the entire plate...). A) The "current" (conduction + displ...
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This document was uploaded on 03/11/2014 for the course PHYSICS 240 at University of Michigan.
 Fall '08
 DaveWinn
 Physics

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