Question

A wire of irregular shape in figure (a) and a circular loop of wire in figure (b) are placed in different uniform magnetic fields as shown in the figures below. In figure (a), the magnetic field is perpendicular into the plane. In figure (b), the magnetic field is perpendicular out of the plane.

The wire in figure (a) is turning into a circular loop and that in figure (b) into a narrow straight wire. The direction of induced current will be _____.
Fill in the blank with the correct answer from the options given below

• A. clockwise in both (a) and (b)
• B. anticlockwise in both (a) and (b)
• C. clockwise in (a) and anticlockwise in (b)
• D. anticlockwise in (a) and clockwise in (b)

Answer 1

The Correct Option is C

Lenz's law dictates the direction of induced current; it opposes the change in magnetic flux. We examine each scenario:

1. Figure (a): An irregular wire deforms into a circular loop. The magnetic field is directed perpendicularly into the plane. As the wire forms a loop, the enclosed area grows, increasing magnetic flux (since the field is constant and perpendicular). To oppose this flux increase, the induced current generates a magnetic field directed out of the plane. Applying the right-hand rule, a magnetic field out of the plane signifies a clockwise current.
2. Figure (b): A circular loop transforms into a narrow straight wire. The magnetic field is directed perpendicularly out of the plane. The reduction in enclosed area as the loop straightens decreases the magnetic flux. To oppose this flux decrease, the induced current must create a magnetic field directed into the plane. The right-hand rule indicates that a magnetic field into the plane corresponds to an anticlockwise current.

Consequently, the induced current direction is clockwise in (a) and anticlockwise in (b).