Definition
A capacitor whose capacitance can be deliberately changed, usually by rotating one set of metal plates so they overlap more or less with a fixed set of plates separated by air or another insulator. Adjusting the overlap changes how much electrical charge the device can store, which in turn changes the frequency the circuit responds to.
Plain English
An electrical part that stores a small amount of energy, built so a knob or shaft can change how much it stores. It is most often used to tune a radio to different frequencies.
Context Anchor
Seen in aircraft electrical and avionics discussions, especially when describing how older radio or tuning circuits work.
Derivation
From Latin 'capacitas,' meaning 'capacity' or 'ability to hold.' A capacitor holds an electrical charge; 'variable' simply means the amount it holds can be changed.
Why Pilots Care
Allows precise tuning of aircraft communication and navigation radios so the correct frequencies can be selected reliably.
Analogy
It is like an adjustable container: instead of changing how much water it can hold, a variable capacitor changes how much electric charge it can hold.
Intuition Check
Variable does not mean the part changes randomly. It means the amount of electric charge it can hold is adjustable by design.
Example Sentence 1
Turning the tuning knob on the older nav radio rotated a variable capacitor inside, changing the frequency it picked up.
Example Sentence 2
During radio troubleshooting the mechanic checked the variable capacitor for smooth adjustment across its full range.