Question

A small hole is made at the centre of the magnet then its magnetic moment

• A. decreases
• B. increases
• C. remains same
• D. depends on the nature of the magnetic material

Answer 1

Answer: (A)

decreases

Answer 2

The magnetic field lines in the hole will be from North pole to South pole where as the magnetic field lines in the magnet will be from South pole to North pole. $\therefore$ The net magnetic field lines inside the magnet get decreased which results in the decrease of the net pole strength which results in the decrease in magnitude of the magnetic moment.