Question

A conducting rod of length is moved at constant velocity `v_(0)` on two parallel, conducting, smooth, fixed rails, that are placed in a uniform constant magnetic field B perpendicular to the plane for the rails as shown in Fig. A resistance R is connected between the two ends of the rails.
Then which of the following is/are correct:

A. the power delivered by force will be constant with time
B. the power delivered by force will be increasing first and will decrease
C. the rate of power delivered by the external force will be increasing continuously
D. the rate ow power delivered by external force will be decreasing continuously before becoming zero.

Answer 1

Correct Answer - D
Force acting on the rod because of the induced current due to change in magnetic flux will try to oppose the motion of rod.Hence the acceleration of the rod will decrease with time `(dP)/(dt)=F(dv)/(dt)=Fxxa`.Thus rate of power delivered by external force will be decreasing continuously.