Question

Choose the wrong option regarding miniature circuit breaker (MCB)?

• A. MCB contains a metal that melts when the current passing through it exceeds a certain value and hence opens the circuit
• B. Quick restoration of an MCB is possible just by switching on the operation when a breakdown occurs due to the current overload
• C. MCB switches off the circuit automatically when the current passing through it exceeds a certain value
• D. None of the above

Answer 1

Answer: (A)

MCB contains a metal that melts when the current passing through it exceeds a certain value and hence opens the circuit

In MCB, whenever continuous current flows, the bimetallic strips are heated and deflect by bending. This deflection of bimetallic strips releases the mechanical latch. It causes to open the miniature circuit breakers contact and the MCB turns of thereby stopping the current to flow in the circuit. Hence $A$ is the wrong statement.