Which statement about alternator excitation is true?

• A. Excitation is provided by an AC circuit
• B. Excitation is provided by a battery only
• C. DC circuit
• D. No external excitation is required

Answer: (C)

The field that creates the magnetic flux in an alternator must be supplied with direct current. That excitation current is provided through a DC circuit, typically from the aircraft’s battery via a voltage regulator (and, in some systems, through a dedicated exciter that rectifies to DC). This DC field current is what produces a steady magnetic field for the stator to generate electricity. It’s not an AC excitation, and it’s not something that would work if there were no external excitation at all. While the battery can help initially, normal operation relies on a DC source feeding the field winding to control and maintain the output.