試題詳解

8. A solid rod with length L, resistance R and mass M initially rotates with angular velocity ω in a uniform magnetic field B. The two ends of the rod are connected by a conducting wire without resistance. According to Lenz's Law, the induced current will oppose the change of magnetic flux. In this case, the induced current will produce a torque to slow down the rotation speed. What is the torque? Take the pivot point as the origin.
(A)
(B)
(C)
(D)
(E)0