Question

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

• A. an alternating sinusoidal current flows through the ammeter A with a time period $T=\frac{2\pi }{\omega }$
• B. a direct current flows in the ammeter A
• C. a time varying non-sinusoidal current flows through
  the ammeter A
• D. no current flows through the ammeter A

Answer 1

The correct option is D

no current flows through the ammeter A

When a bar magnet rotates about its axis no change in magnetic field occur, so no change occurs in flux and thus no current flows through the ammeter A.

Final Answer: Option (B)