A protective device inserted in series with a circuit that melts if too much current passes through is called what?

• A. Resistor
• B. Capacitor
• C. Circuit Breaker
• D. Fuse

Answer: (D)

A fuse is a protective device placed in series with a circuit that opens when the current becomes too high by melting a thin fusible link. The idea is simple: the link is designed to carry the normal current, but when overcurrent heats it enough, the metal melts and the circuit is permanently opened, preventing damage to wires and components or fire hazards. This sacrificial element provides fast, simple overcurrent protection and is, by design, a single-use device that must be replaced after it “blows.”

Resistors are meant to limit or drop voltage and current within a circuit, not to open the circuit when demand is excessive. Capacitors store and release electrical energy, not protect against overcurrent by melting. Circuit breakers offer protection too, but they operate by sensing fault current and mechanically or magnetically trip to interrupt the circuit; they can be reset after tripping and do not rely on melting a link.