Answer
a. Counterclockwise.
b. $ 1.51\times10^{-4}W$.
Work Step by Step
a. The field is out of the page and the flux is decreasing. By Lenz’s Law, the field caused by the induced current is directed to oppose the change in flux.
The induced current makes a field that is directed out of the page, to help out the failing field. By the right hand rule, the induced current is counterclockwise.
b. Use Faraday’s law to find the emf’s magnitude.
$$|\epsilon|=|\frac{d\Phi}{dt}|=\pi r^2|\frac{dB}{dt}|$$
$$|\epsilon|=\pi (0.0480m)^2(0.680T/s)=4.922\times10^{-3}V$$
Divide emf by the resistance to find the current.
$$I=\frac{4.922\times10^{-3}V }{0.160\Omega}=0.03076A$$
Finally, calculate the rate of energy dissipation.
$$P=I^2R=(0.03076A)^2(0.160\Omega)=1.51\times10^{-4}W$$
