Definition
A drawing that shows the components of an electrical or electronic circuit and the way they are connected to one another, using standardized symbols for items such as resistors, switches, batteries, and wires.
Plain English
A picture of an electrical circuit that uses simple symbols to show every part and how they are wired together.
Context Anchor
Seen in aircraft maintenance manuals, wiring information, and troubleshooting references for electrical equipment.
Derivation
Circuit comes from the Latin circuitus, meaning 'a going around.' An electrical circuit is a complete loop that current travels around. A diagram is simply a drawing that explains how something is arranged. So a circuit diagram is a drawing that shows the loop.
Why Pilots Care
Accurate circuit diagrams allow quick identification of electrical faults that could affect lights, radios, instruments, or engine starting systems.
Intuition Check
Do not read a circuit diagram as a picture of where the wires are physically located in the airplane. It mainly shows what is connected to what and how electricity is meant to move through the system.
Example Sentence 1
The technician pulled out the circuit diagram to trace why the landing light was not working.
Example Sentence 2
Before installing the new transponder, the mechanic reviewed the circuit diagram in the maintenance manual to locate the correct power source.