A circular loop of wire with radius 0.0430 m and resistance 0.156 Ohms is in a r

Question

A circular loop of wire with radius 0.0430 m and resistance 0.156 Ohms is in a region of spatially uniform magnetic field, as shown in the following figure . The magnetic field is directed out of the plane of the figure. The magnetic field has an initial value of 8.03 T and is decreasing at a rate of -0.634 T/s.http://session.masteringphysics.com/problemAsset/1331233/7/2920.jpg

Part A: Is the induced current in the loop clockwise or counterclockwise?

Part B: What is the rate at which electrical energy is being dissipated by the resistance of the loop?

Explanation / Answer

r = 0.0430 m, R = 0.156 , B0 = 8.03 T, dB/dt = -0.634 T/s

Part A: Is ?

dB/dt < 0, by Lenz law, the direction of the magnetic field due to induced current is same as B, or out of page.

By right-hand rule, the induced current in the loop is counterclockwise.

Part B: What is the rate at which electrical energy U is being dissipated by the resistance of the loop?

induced emf = -(r2)*dB/dt

induced current I = /R

the rate = I2R = (r2)2(dB/dt)2/R = 8.69*10-5 W

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