Which lead completes the circuit from the power source through the aircraft structure?

Which lead completes the circuit from the power source through the aircraft structure?

• A. Negative lead
• B. The positive lead
• C. Ground lead
• D. Return path through the control panel

Answer: (B)

The key idea is that electricity must be supplied from the power source and then return to it to form a closed loop. The positive lead is the conductor that provides the energy to the circuit, delivering current into the loads (and through the aircraft structure if it’s used as part of the return path). The current then returns to the power source via the appropriate return path, completing the circuit. In this context, the positive lead is the element that starts and effectively completes the energy delivery cycle, which is why it’s the best choice. The other options describe paths for returning current or grounding, not the initiating supply that energizes the circuit.

The key idea is that electricity must be supplied from the power source and then return to it to form a closed loop. The positive lead is the conductor that provides the energy to the circuit, delivering current into the loads (and through the aircraft structure if it’s used as part of the return path). The current then returns to the power source via the appropriate return path, completing the circuit. In this context, the positive lead is the element that starts and effectively completes the energy delivery cycle, which is why it’s the best choice. The other options describe paths for returning current or grounding, not the initiating supply that energizes the circuit.