Definition
A capacitor placed in a power supply or electronic circuit to smooth out voltage variations by storing electrical charge during peaks and releasing it during dips, reducing ripple and unwanted fluctuations in the output.
Plain English
A small electrical part that evens out a bumpy voltage so the circuit gets a steady supply instead of one that rises and falls.
Context Anchor
Seen in aircraft electrical system, radio, alternator, generator, ignition, and power-supply discussions.
Derivation
‘Filter’ comes from the everyday idea of straining something to remove what you don’t want. ‘Capacitor’ comes from Latin capax, meaning ‘able to hold.’ Together: a part that holds charge in order to strain out the unwanted ups and downs in voltage.
Why Pilots Care
Electrical noise from generators or alternators can produce radio static and erratic instrument readings; the filter capacitor removes that noise before it reaches critical equipment.
Analogy
Think of a small water tank between a hand pump and a tap. The pump pushes water in pulses, but the tank keeps the tap flowing smoothly. The capacitor does the same thing for electricity.
Intuition Check
A filter capacitor does not filter air, oil, or fuel. It filters electrical disturbances by smoothing unwanted voltage changes.
Example Sentence 1
The technician replaced a failed filter capacitor in the radio’s power supply, and the static in the headset disappeared.
Example Sentence 2
During the electrical system check, the technician tested the filter capacitor for leakage that could allow noise into the avionics bus.