What is a fusible link and its purpose in aircraft electrical systems?

• A. A sacrificial conductor that melts under excessive current to protect wiring and components.
• B. A fuse that automatically resets after overheating.
• C. A switch that manually opens the circuit.
• D. A sensor for temperature.

Answer: (A)

The concept being tested is protection of aircraft wiring with a sacrificial conductor that interrupts the circuit when overload occurs. A fusible link is a short piece of conductor designed with a low-melting-point material in its insulation. When excessive current flows, the heat melts the link and the circuit opens, shielding wiring and components from damage. It’s not resettable; once it opens, it must be replaced. This is different from a device that resets on its own, a manual switch, or a temperature sensor, which serve other roles in the system.