Question

An MCB which cuts off the electricity supply in case of short-circuiting or overloading works in the:

(a) chemical effect of current
(b) heating effect of current
(c) magnetic effect of current
(d) electroplating effect of current

Answer 1

(c) magnetic effect of current

MCB contains an electromagnet. When current increases heavily, the electromagnet becomes strong enough to separate the pair of contacts and break the circuit.