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?
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current, loop B has no induced current, and loop C has counterclockwise current.
E)Loop A has counterclockwise current, loop B has no induced current, and loop C has clockwise current.

Question

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? 
A)No current is induced in any loop. 
B)The currents are counterclockwise in all three loops. 
C)The currents are clockwise in all three loops. 
D)Loop A has clockwise current, loop B has no induced current, and loop C has counterclockwise current. 
E)Loop A has counterclockwise current, loop B has no induced current, and loop C has clockwise current.

Quizplus · Accepted Answer

According to Faraday's law, a changing magnetic field induces an electric field, which in turn causes a current to flow in a closed loop. The direction of the induced current is determined by Lenz's law, which states that the current will flow in a direction that opposes the change in the magnetic field that caused it.

In this case, as the current in the wire decreases, the magnetic field around the wire decreases as well. Applying the right-hand rule, we can see that this change in the magnetic field will cause the magnetic flux through loop A to increase (clockwise), the flux through loop B to remain constant (no induced current), and the flux through loop C to decrease (counterclockwise). Therefore, the induced currents in loops A and C will be counterclockwise and clockwise, respectively, while no current is induced in loop B.

Therefore, the correct answer is choice E.

The Wire in the Figure Carries a Current I That