A cylindrical bar magnet is rotated about its axis (Figure). A wire is connect from the axis and is made to touch the cylindrical surface through a contact. Then

Options

A. a direct current flows in the ammeter A
B. no current flows through the ammeter A
C. an alternating sinusoidal current flows through the ammeter A with a time period `T = (2 pi)/(omega)`
D. a time varying non-sinusoidal current flows through the ammeter A

Answer

B

Explanation

When the cylindrical bar magnet is rotated about its axis, there is no change in the magnetic flux linked with the circuit. Hence the induced e.m.f. = 0.
`:.` no current flows through the ammeter A. [Option (b)].