What is the safety device that melts when the current exceeds a specified value?

What is the safety device that melts when the current exceeds a specified value?

• A. Circuit breaker
• B. Fuse
• C. Thermal fuse
• D. Overload switch

Answer: (B)

A fuse is designed for overcurrent protection by letting a conductor link carry current up to its rating, then melt and open the circuit when the current becomes too high. The heat generated by excess current causes the fusible material to reach its melting point, breaking the connection and stopping the flow of electricity. It’s a one-time protection device: once it blows, it must be replaced. This contrasts with a circuit breaker, which trips a mechanism (thermally or magnetically) to interrupt current and can be reset, rather than melting. A thermal fuse opens when a specific temperature is reached, which can be caused by high current but is a temperature-threshold device rather than a fixed current rating. An overload switch serves as a protective switch that trips on overload conditions as well, but it’s not defined by a melting fusible link.

A fuse is designed for overcurrent protection by letting a conductor link carry current up to its rating, then melt and open the circuit when the current becomes too high. The heat generated by excess current causes the fusible material to reach its melting point, breaking the connection and stopping the flow of electricity. It’s a one-time protection device: once it blows, it must be replaced.

This contrasts with a circuit breaker, which trips a mechanism (thermally or magnetically) to interrupt current and can be reset, rather than melting. A thermal fuse opens when a specific temperature is reached, which can be caused by high current but is a temperature-threshold device rather than a fixed current rating. An overload switch serves as a protective switch that trips on overload conditions as well, but it’s not defined by a melting fusible link.