Question

A rectangular coil of metallic wire is rotated in a magnetic field. The direction of the induced current changes once in each:

• A. two revolutions.
• B. one revolution.
• C. half revolution.
• D. one-fourth revolution.

Answer 1

The correct option is C half revolution.

Consider coil of metallic wire rotating in a magnetic field initially parallel to the magnetic field. The magnetic field lines increases in the first half cycle and hence the direction of current is in positive cycle. After half the cycle, the magnetic field lines through the coil is maximum. Beyond this point, the magnetic field lines through the coil starts to reduce and the direction of current is reversed. This is a continuous process and hence, the direction of induced current changes after every half revolution of the coil.