Definition
Capacitance is the property of an electrical circuit, or component, to store an electric charge when a voltage is applied across it. It is measured in farads (F), where one farad equals one coulomb of charge stored per volt applied. In aircraft electrical systems, capacitance is provided by capacitors — components built from two conductive plates separated by an insulating material called a dielectric.
Plain English
Capacitance is how much electrical charge a part can hold for a given voltage. The bigger the capacitance, the more charge it can store before it is full.
Context Anchor
Seen in aircraft electrical-system study, wiring diagrams, capacitor checks, ignition-system discussions, and avionics maintenance.
Derivation
From the Latin capacitas, meaning 'ability to hold or contain.' The same root gives us 'capacity.' In electrical terms, it is the circuit's capacity to hold electric charge — so the everyday meaning of 'how much it can hold' carries straight over.
Why Pilots Care
Capacitors smooth out electrical noise, store energy for ignition systems, and protect sensitive avionics. Understanding capacitance helps a technician troubleshoot radios, instruments, and ignition components when they behave erratically.
Analogy
Think of capacitance like the size of a small bucket sitting under a tap. A bigger bucket (more capacitance) holds more water (charge) for the same water pressure (voltage).
Intuition Check
Capacitance does not mean battery power or total electrical energy available. It means the ability to store electric charge in an electrical field.
Example Sentence 1
The technician replaced a failed capacitor in the radio's power supply because its capacitance had dropped below the specified value.
Example Sentence 2
A drop in capacitance can cause the ignition system to perform poorly during engine start.