If the positive field lead between a generator and the control panel breaks and shorts while the engine is running, what will a voltmeter show?

When the positive field lead between the generator and the control panel breaks and shorts while the engine is running, the voltmeter is likely to show residual voltage. This is because residual voltage refers to the small amount of voltage that remains in the electrical system even after a disconnection occurs.

In the case of a generator, it might still have some residual magnetism in the field windings. This residual magnetism can produce a small voltage across the terminals, which is what the voltmeter would detect. Thus, while the circuit is compromised due to the broken lead, the remaining magnetic field can still generate some voltage, leading to a reading of residual voltage rather than zero voltage or normal voltage.

Understanding this behavior is crucial for diagnosing electrical issues in aircraft, as it helps identify the condition of the electrical system and whether the generator is still capable of providing some output despite the break in the circuit.