Question

A permanent magnet can be demagnetised using current. This is done by

• A. Placing the magnet in a solenoid carrying direct current such that the solenoid points East-West
• B. Placing the magnet in a solenoid carrying alternating current such that the solenoid points East-West
• C. Placing the magnet in a solenoid carrying direct current such that the solenoid points North-South
• D. Placing the magnet in a solenoid carrying alternating current such that the solenoid points North-South

Answer 1

The correct option is B

Placing the magnet in a solenoid carrying alternating current such that the solenoid points East-West

To demagnetise a permanent magnet place it inside a solenoid, pointing East-West, through which an alternating current is flowing. While the current is still flowing, the small atomic magnets present in the permanent magnet get disoriented and hence the permanent magnet gets demagnetised.