Question

An MCB works on the principle of ___ effect of electric current.

Answer 1

MCBs are used in houses to protect the household wiring from excessive flow of electric current through it. If the current becomes too large, the miniature circuit breaker automatically switches off the switch, cutting off the electric supply.
The MCB can be reset when the fault has been corrected. MCB contains an electromagnet which becomes strong enough to separate a pair of contacts and thus breaks the circuit when the current exceeds the rated value. So, MCBs work on the magnetic effect of electric current.