Question

Assertion (A): An MCB works on the magnetic effect of current.

Reason (R): During short-circuiting, when too much current flows through the circuit, the thin fuse wire in MCB gets heated, melts and breaks the circuit so as to prevent an electrical fire.

Options

• Both A and R are true and R is correct explanation of the assertion.

• Both A and R are true but R is not the correct explanation of the assertion.

• A is true but R is false.

• A is false but R is true.

Answer 1

A is true but R is false.

Explanation:

The assertion is true because a Miniature Circuit Breaker (MCB) utilises an electromagnet to automatically trip the switch when current exceeds safe limits. However, the reason is false because an MCB does not contain a fuse wire that melts; instead, it uses a magnetic mechanism or a bimetallic strip to break the circuit mechanically, allowing it to be easily reset without replacement.