Question

why does an overloaded electric circuit catch fire​

Answer 1

Overloaded electrical outlets, or circuits that supply power to several outlets, is a major cause of residential fires. ... The heat causes wear on the internal wiring system and can ignite a fire. All wiring systems have circuit breakers or fuses that disconnect power when circuits become overloaded.

Answer 2

an overloaded circuit catches fire when the wires or the appliance is not capable in carrying higher volts. this the reason why  an overloaded electric circuit catch fire​