What is a circuit breaker in aircraft electrical systems?

• A. A device that controls engine fuel flow
• B. A current-limiting device (a fuse) that can be reset. A system used in electrical circuits to prevent the system from overloading
• C. A device that opens the cabin door
• D. A device that measures cabin temperature

Answer: (B)

In aircraft electrical systems, the main idea is protection of circuits from damage due to overload or faults. A circuit breaker acts as a protective switch that automatically interrupts the electric current when it detects excessive current or a fault on a circuit. Unlike a fuse, which is single-use, a circuit breaker can be reset after the fault is addressed, allowing power to be restored to the circuit once the underlying issue is resolved. This resettable protection helps prevent wiring insulation from overheating and protects equipment, while giving crew a way to bring nonessential systems back online after troubleshooting. It’s not used to control engine fuel, open cabin doors, or measure cabin temperature, which is why those other functions don’t fit.