Fall 2012 Midterm 3 Solutions

# We have to work backwards through the three

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Unformatted text preview: hrough the three transformers. 13. An electric field E E0 cos(2 ft ) is applied along the axis of a cylindrical semiconductor of cross-sectional area A=20 cm2 and resistivitym At what frequency, f, are the amplitudes of the conduction and displacement currents equal? (1 Hz = 1 cycle/s) A) 5.0 x 109 Hz B) 4.0 x 103 Hz C) 2.0 x 1011 Hz D) 8.0 x 105 Hz E) 9.0 x 108 Hz Set the amplitudes equal to each other and solve for f. Version 1 Page 8 14. Two concentric circular loops of wire lie in a plane. The inner loop radius, r = 0.1 m, is much smaller than the outer loop radius of R = 2 m. What is the approximate mutual inductance of this configuration of two loops? r A) B) C) D) E) R Strategy: estimate the flux through the smaller loop by assuming that the magnetic field at the center of the larger ring is uniform over the area of the smaller one. Use this flux in the definition of inductance to calculate inductance. 5.2 x 10-8 H 8.4 x 10-7 H cannot determine without knowing the current in the outer loop 9.9 x 10-9 H cannot determine without knowing the rate change of current in the outer loop Note: the mutual inductance is the part of the flux calculation that does NOT depend on current. You do not need to know the current to calculate it. We gave half credit to the two incorrect NUMERIC answers (A and B on this version). 15. The switch in the circuit below has been closed for a long time. Immediately after opening the switch wha...
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## This document was uploaded on 03/11/2014 for the course PHYSICS 240 at University of Michigan.

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