How does a fuse differ from a circuit breaker in aircraft wiring?

How does a fuse differ from a circuit breaker in aircraft wiring?

• A. A fuse is a one-time protective device that opens the circuit when overloaded
• B. A circuit breaker is a reloadable protective device that trips on overload or short and can be reset
• C. Fuses can be reset after tripping
• D. Circuit breakers open only on short circuits and cannot be reset

Answer: (A)

Fuses and circuit breakers are both protective devices, but they operate differently. A fuse has a thin metal element that carries the circuit current; when the current exceeds its rated value, the element heats up and melts, opening the circuit. Once a fuse has blown, it cannot be reset or reused—you must replace it. That makes fuses a one-time protective device. A circuit breaker, on the other hand, is a reclosable switch. It senses overload or a short and trips open, but it can be reset after the fault is cleared, restoring power to the circuit. This reusability is why breakers are common in aircraft wiring for many circuits, while fuses are used where a one-time interrupt is acceptable. So the key difference is one-time use versus resettable. The other statements claim resets for fuses or that breakers cannot be reset, which don’t reflect how these devices actually function.

Fuses and circuit breakers are both protective devices, but they operate differently. A fuse has a thin metal element that carries the circuit current; when the current exceeds its rated value, the element heats up and melts, opening the circuit. Once a fuse has blown, it cannot be reset or reused—you must replace it. That makes fuses a one-time protective device.

A circuit breaker, on the other hand, is a reclosable switch. It senses overload or a short and trips open, but it can be reset after the fault is cleared, restoring power to the circuit. This reusability is why breakers are common in aircraft wiring for many circuits, while fuses are used where a one-time interrupt is acceptable.

So the key difference is one-time use versus resettable. The other statements claim resets for fuses or that breakers cannot be reset, which don’t reflect how these devices actually function.