What type of device serves to protect electrical circuits from overload?

A fuse is a fundamental safety device designed to protect electrical circuits from overloads and short circuits. It operates on the principle of melting a wire or strip of metal within its casing when a current exceeding its rated capacity flows through it. This melting action interrupts the flow of electricity, effectively preventing damage that could be caused by excessive current, such as overheating or fire hazards.

The other choices, while all related to electrical systems, serve different purposes. A transformer is used to change the voltage level in a circuit, a generator converts mechanical energy into electrical energy, and a capacitor stores electrical energy for later use or smooths out fluctuations in voltage. None of these devices provide the overcurrent protection that a fuse is specifically designed for, which is why the fuse is the correct answer.