Question

Assertion(A): When an iron piece is magnetised, its length slightly increases.

Reason(R): The closed molecular chains break down and all molecules align themselves in the direction of external magnetic field.

• A. A and R are true and R is the correct explanation of A.
• B. A and R are true but R is not the correct explanation of A.
• C. A is true but R is false.
• D. Both A and R are false.

Answer 1

The correct option is A

A and R are true and R is the correct explanation of A.

The explanation for assertion:

1. The magnetization of iron occurs due to the alignment of electrons present in it in one direction.
2. It is done by rubbing the north pole of a magnet from the center to the end of the iron.
3. When an iron piece is magnetized, its length slightly increases.

The explanation for the reason:

1. The reason behind the increase in length of the iron piece is that the closed molecular chains break down.
2. Then all molecules align themselves in the direction of the external magnetic field.

Both the assertion and the reason are true and the reason is the correct explanation of the assertion.

Hence, the correct option is (A).