What device protects a circuit from excessive current?

A fuse is designed specifically to protect a circuit from excessive current. Its function is to break the circuit when the current exceeds a certain pre-determined level. This is achieved through a metal wire or a strip that melts and opens the circuit when the current flowing through it becomes too high. By doing so, a fuse prevents damage to components and circuits that could be caused by overheating or overcurrent conditions. This safety feature is critical in preventing electrical fires and equipment failures.

In contrast, batteries provide power to the circuit, resistors limit current flow but are not primarily for protection, and capacitors store and release electrical energy but do not provide overcurrent protection.