Definition
An electrical circuit in which the current periodically reverses direction, flowing first one way and then the other in a repeating cycle. AC circuits are characterized by properties such as frequency (cycles per second), voltage, and impedance, and they may include resistive, inductive, and capacitive components that affect how the current behaves.
Plain English
A circuit in which the electricity flows back and forth instead of in just one direction. The flow keeps switching direction many times each second.
Context Anchor
Seen in aircraft electrical-system descriptions, wiring diagrams, and maintenance troubleshooting.
Derivation
Circuit' comes from the Latin 'circuitus,' meaning 'a going around.' That fits well here: the electricity travels around a complete loop. 'Alternating' simply means switching back and forth, which describes how the current moves in this kind of circuit.
Why Pilots Care
Many aircraft systems rely on AC power for efficient distribution; understanding these circuits helps identify and fix electrical problems that could affect instruments or radios.
Intuition Check
Do not read circuit as a racetrack or training pattern here. In this context, a circuit is an electrical path that allows current to flow.
Example Sentence 1
The technician checked the AC circuit feeding the cabin lighting after the crew reported intermittent flickering.
Example Sentence 2
During preflight, the mechanic verified that the AC circuit breakers were set correctly before powering up the avionics.