Which safety device protects against overloads in electrical circuits?

A fuse serves as a critical safety device in electrical circuits by protecting against overloads. When current flows through a circuit and exceeds the fuse's rated capacity, the metal wire inside the fuse melts, thereby cutting off the electrical supply to prevent damage to the circuit or potential fire hazards. This self-resetting mechanism ensures that once the fuse blows, the circuit is interrupted until the fuse is replaced, effectively safeguarding the entire system from excess current that could damage components or create dangerous conditions.

In contrast, other devices mentioned, like relays, switches, and contactors, have different functions. A relay is primarily used to control a larger circuit with a smaller current, often providing an automatic control mechanism rather than directly protecting against overloads. A switch simply opens or closes a circuit but does not provide overload protection. Similarly, a contactor is used to control high current loads but also does not inherently protect against overload situations; it may work in conjunction with overload relays for that purpose. Therefore, the fuse stands out as a dedicated and reliable safety feature designed specifically for the protection against overloads in electrical circuits.