What device in an electrical system melts to prevent overheating?

A fuse is a safety device that plays a crucial role in preventing electrical overload and potential fires within an electrical system. It contains a metal wire or strip that melts when the current flowing through it exceeds a certain threshold, effectively interrupting the electrical circuit. This melting action prevents overheating by stopping the flow of electricity, thereby protecting the wiring and connected devices from damage caused by excessive current.

Fuses are designed to respond quickly to short circuits or overloads, providing a simple yet effective means of circuit protection. Once a fuse has melted due to an overload, it must be replaced to restore the electrical circuit, ensuring continued safety in the system.

In contrast, other devices mentioned serve different functions. A circuit breaker automatically interrupts the flow of current when it detects an overload, allowing for reset and reuse. A transformer adjusts voltage levels in electrical systems without providing protection from current overload. A relay acts as a switch to control larger power loads but does not prevent overheating on its own. Understanding the specific roles of each device helps clarify why a fuse is the correct answer in this context.