Definition
A complete path through which electric current can flow, starting from a power source, passing through one or more electrical components, and returning to the source. A circuit must form a closed loop for current to flow; if the loop is broken at any point, the circuit is open and no current flows.
Plain English
A loop that lets electricity flow from a power source, through whatever it is powering, and back again. If the loop is unbroken, things work. If the loop is broken anywhere, nothing flows.
Context Anchor
Seen in aircraft electrical system descriptions, wiring diagrams, checklist items, and circuit breaker discussions.
Derivation
From the Latin 'circuitus,' meaning 'a going around.' The same root gives us 'circle.' It captures the key idea: electricity has to travel around a complete loop and return to where it started.
Why Pilots Care
Maintains orderly traffic flow and separation at busy or uncontrolled airports.
Analogy
Think of a circuit like a simple loop road. If the road is blocked, traffic cannot complete the loop; if an electrical circuit is broken, electricity cannot complete its path.
Grounding Statement
Picture a battery with a wire running out one terminal, through a light bulb, and back into the other terminal. That loop is a circuit. Cut the wire anywhere and the bulb goes dark.
Intuition Check
Do not read “circuit” here as a racetrack lap or a general route around an area. In aircraft electrical use, it means the path electricity follows to power equipment.
Example Sentence 1
When the landing light stopped working, the mechanic traced the circuit and found a broken wire behind the instrument panel.
Example Sentence 2
With two aircraft already on downwind, the student extended the leg to maintain safe spacing in the circuit.