What type of device is commonly used to protect against overcurrent?

A fuse is a device specifically designed to protect electrical circuits from overcurrent conditions. It works by breaking the circuit when the current exceeds a predetermined level. When too much current flows through the fuse, its metal wire or filament melts, interrupting the circuit and preventing damage to the wiring and connected devices. This protective measure is crucial in preventing fires and equipment failure due to excessive current.

Other devices listed, such as a voltage regulator, transformer, and relay, serve different functions. A voltage regulator maintains a constant voltage level, a transformer changes voltage levels between circuits, and a relay acts as a switch controlled by an electrical signal. While these devices are essential in various electrical applications, they do not specifically provide overcurrent protection as a fuse does.