Which device is used to prevent electrical overload?

A fuse is a safety device specifically designed to prevent electrical overload by interrupting the electrical circuit when the current exceeds a predetermined level. It functions by melting a metal wire or strip within the fuse casing when excessive current flows through it. This disconnection of the circuit helps protect both the wiring and devices connected to it from damage due to overheating, which could lead to potential hazards such as electrical fires.

Other devices mentioned in the options have different functions. A socket is merely a point where electrical devices can connect to the power supply, and it does not provide any overload protection. A relay acts as a switch that opens or closes a circuit based on an input signal, but it does not prevent overload on its own. A capacitor stores electrical energy temporarily and is used in various applications such as filtering and power factor correction, but it does not serve to protect against overload conditions. Therefore, the fuse is the device that directly addresses the issue of electrical overload.