Definition
An electrical charge that remains stored in a capacitor or other component after the power source has been disconnected. Because a capacitor holds energy in its dielectric, it can retain a dangerous voltage for some time after a circuit is switched off, and must be deliberately discharged before the component is handled or tested.
Plain English
Leftover electricity still sitting inside a part — usually a capacitor — even after the power has been turned off. It can give you a shock or damage test equipment if you touch it before draining it.
Context Anchor
Seen in aircraft electrical maintenance, especially when working near parts that can store electrical energy even after power is removed.
Derivation
Residual comes from the Latin residuum, meaning 'that which is left behind.' It points directly to the idea that some charge stays behind after the main power is removed.
Why Pilots Care
Uncontrolled discharge of residual charge can damage sensitive avionics or cause injury during maintenance.
Grounding Statement
A part can still hold a small amount of electrical energy even when the aircraft switch is off.
Intuition Check
Residual charge does not mean the aircraft electrical system is still on. It means a part may still be holding leftover electrical energy after power has been removed.
Example Sentence 1
Before removing the radio, the technician shorted the capacitor terminals to bleed off any residual charge.
Example Sentence 2
Even with the battery master off, residual charge in the system can still deliver a shock if leads are shorted.