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

Answer: (C)

clockwise in (a) and anticlockwise in (b)

Answer 2

According to Lenz’s law, the induced current will oppose the change in magnetic flux. In figure (a), as the wire turns into a circular loop, the area of the loop increases, increasing the magnetic flux into the plane. To oppose this increase, the induced current wil be clockwise. In figure (b), the wire is turning into a straight line, decreasing the area and the magnetic flux out of the plane, so the induced current will be anticlockwise to oppose this change.