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

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

Miniature Circuit Breakers (MCBs) is an automatically operated electrical switch which contains an electromagnet. When current increases heavily, the electromagnet becomes strong enough to separate the pair of contacts and break the circuit.

It is used to protect low voltage electrical circuits from damage caused by excess current from an overload and short circuit.