Which device serves to protect against overcurrent in electrical circuits?

The device that serves to protect against overcurrent in electrical circuits is a circuit breaker. A circuit breaker is designed to automatically interrupt the flow of electricity when it detects a current that exceeds a pre-set level. This protects wiring and connected devices from damage caused by excessive current that could lead to overheating, fires, or other hazards.

When an overcurrent situation arises, the circuit breaker responds by opening the circuit, thus stopping the flow of electricity and preventing potential damage. This functionality allows for easy resetting after the fault is cleared, making circuit breakers a preferred choice in many electrical systems.

Fuses also protect against overcurrent but operate differently. A fuse consists of a metal wire or strip that melts when excess current flows, thus breaking the circuit permanently until the fuse is replaced. Transformers, on the other hand, are used to change voltage levels and do not provide protection against overcurrent. Relays are primarily control devices that use a low-power signal to operate or switch on/off circuits but do not inherently protect against overcurrent on their own.