The wire in the figure carries a current I that is decreasing with time at a constant rate.The wire and the three loops are all in the same plane.What is true about the currents induced in each of the three loops shown?

Question

Quizplus · Accepted Answer

According to Lenz's Law, the direction of the induced current in a loop opposes the change that produced it. In this case, the current in the wire is decreasing, so the induced current in each loop will flow in a direction such that it creates a magnetic field that opposes the decrease in the magnetic field caused by the decreasing current in the wire.

For loop A, the induced current will create a magnetic field pointing into the plane of the paper, opposing the decreasing magnetic field caused by the wire. The direction of this induced field can be achieved by the current flowing counterclockwise in loop A.

For loop B, there is no change in the magnetic field through it as the wire current decreases. Therefore, no current will be induced in this loop.

For loop C, the induced current will create a magnetic field pointing out of the plane of the paper, opposing the decreasing magnetic field caused by the wire. The direction of this induced field can be achieved by the current flowing clockwise in loop C.

Thus, the current induced in loop A is counterclockwise, in loop B there is no current induced, and in loop C the current induced is clockwise. Therefore, the best choice is E.

The Wire in the Figure Carries a Current I That