Question

Assertion (A): When a permanent bar magnet is placed in a solenoid connected to a.c. source, it gets demagnetised.

Reason (R): The alternating current rapidly changes the magnetic polarity which in turn disturbs magnetic molecular straight chains, to form closed chains and hence demagnetise the magnet.

Options

• Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

• Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).

• Assertion (A) is false, but Reason (R) is true.

• Assertion (A) is true, but Reason (R) is false.

Answer 1

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Explanation:

The alternating current produces a rapidly changing magnetic field in the solenoid, so the bar magnet is magnetised in opposite directions again and again and gets demagnetised. This changing polarity disturbs the aligned molecular magnets of the magnet and makes them form closed chains. Hence, Reason correctly explains Assertion.