Question

Choose the wrong option regarding miniature circuit breaker (MCB)?
A) MCB contains a metal which 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 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

Hint: A miniature circuit breaker is an electromagnetic device. It provides a complete enclosure in a molded insulating material. MCB’s main function is to switch off and on the circuit. The switch is opened automatically when the current passes through it if it exceeds the value. Using these statements determine which statement is wrong among the given options.

Complete step by step solution:
MCB is used to operate automatically a switch that is used to protect the circuits from low voltage. A miniature circuit breaker is an electromagnetic device. It provides a complete enclosure in a molded insulating material.
MCB’s main function is to switch off and on the circuit. The switch is opened automatically when the current passes through it if it exceeds the value. MCB automatically switches off the circuit during both overload and fault conditions. It is mainly reliable in the detection of such conditions. It is sensitive to the change in current.
Since the switch in MCB is off during tripping the faulty part of the circuit can easily be identified. MCB can detect a fault better when compared to the fuse. MCB has a quick restoration by flipping a switch. MCB can be remotely controlled.
When there is a continuous current flow the MCB has a bimetallic latch. These bimetallic strips are heated and deflected by heating. Then the bimetallic strips release a metallic latch. It will make the latch to open the miniature circuit breaker contact and the MCB stops the current flowing through the circuit.

Then we can say that option $\left( A \right)$ is the wrong statement.

Note: MCB is preferred more than the fuses nowadays. Fuse has no quick restoration and it is difficult to detect the fault in the circuit when the circuit is tripped. MCB is used to operate automatically a switch that is used to protect the circuits from low voltage. A miniature circuit breaker is an electromagnetic device. It provides a complete enclosure in a molded insulating material.