Definition
An electrical circuit that has a break in its conductive path, preventing current from flowing. The break may be intentional, such as an open switch, or unintentional, such as a broken wire, blown fuse, or loose connection.
Plain English
A circuit that is not complete, so electricity has no path to flow through. Whatever the circuit was supposed to power will not work.
Context Anchor
Seen in aircraft electrical system discussions, maintenance write-ups, and troubleshooting when a light, radio, pump, or other electrical item does not work.
Derivation
From the everyday sense of 'open' meaning 'not closed' — the loop is open, so the path is broken. A 'closed circuit' is the opposite: a complete loop where current can flow.
Why Pilots Care
An open circuit can disable essential systems such as radios, navigation lights, or instruments, creating an immediate safety or airworthiness issue.
Analogy
It is like a drawbridge raised on a road. The road exists on both sides, but traffic cannot cross because the path is not complete.
Intuition Check
Open does not mean “available for electricity to use” here. In an electrical circuit, open means the path is broken, so current cannot flow.
Example Sentence 1
The landing light failed to illuminate because a broken wire created an open circuit between the switch and the bulb.
Example Sentence 2
After replacing the fuse the mechanic traced the remaining fault to an open circuit behind the instrument panel.