Definition
A fixed-value capacitor in which the dielectric (the insulating layer between the two conductive plates) is made of paper, often impregnated with wax or oil to improve its insulating properties. The plates are typically thin metal foil, and the paper-and-foil sandwich is rolled into a compact cylinder and sealed inside a tubular case.
Plain English
A small electrical part that stores a charge, built by rolling up two strips of metal foil separated by a strip of paper. The paper keeps the two foils from touching while still letting them work together to hold electricity.
Context Anchor
Seen in aircraft electrical maintenance, especially when inspecting or repairing older radios, ignition noise filters, and legacy electrical equipment.
Derivation
The term simply names the dielectric material. Calling it a 'paper' capacitor distinguishes it from capacitors that use mica, ceramic, plastic film, or electrolyte as the insulating layer.
Why Pilots Care
Paper capacitors appear in legacy aircraft electrical components; knowing their construction helps identify failure modes during maintenance of vintage equipment.
Analogy
Think of two sheets of foil with a thin dry sheet between them. The foil can hold opposite electrical charges, while the sheet keeps them from touching. A paper capacitor uses that same basic idea, but with treated paper and metal layers made for electrical use.
Intuition Check
Do not picture ordinary notebook paper being used loosely inside the airplane. In a paper capacitor, the paper is treated and sealed so it can act as an electrical insulator.
Example Sentence 1
The technician traced the radio's hum to a leaky paper capacitor in the power supply and replaced it.
Example Sentence 2
Early model aircraft often used paper capacitors in the magneto booster circuit.