Definition
A capacitor connected across a component or power supply line to provide a low-impedance path to ground for unwanted alternating current (AC) signals or electrical noise, while allowing the direct current (DC) to pass through the circuit normally.
Plain English
A small electrical part placed across a circuit that lets steady direct current through but routes electrical noise and unwanted ripples away to ground, keeping the circuit clean and stable.
Context Anchor
Seen in aircraft electrical systems, avionics, radio-noise troubleshooting, and maintenance discussions of circuit protection and filtering.
Derivation
From 'bypass' (to go around) and 'capacitor' (a device that stores electrical charge). The name describes its job: it gives unwanted AC signals a path to go around the main component instead of through it.
Why Pilots Care
Reduces static and noise in radios and sensitive instruments, helping maintain clear communications and reliable readings.
Analogy
It is like a drain beside a road after heavy rain. The normal traffic keeps moving on the road, while the extra water is given an easier path away from it.
Intuition Check
A bypass capacitor is not a backup battery and it does not bypass the whole electrical system. It only gives certain unwanted electrical changes an easier path around a part of a circuit.
Example Sentence 1
The avionics technician replaced a failed bypass capacitor that was allowing alternator noise to leak into the audio panel.
Example Sentence 2
A failed bypass capacitor allowed engine electrical noise to reach the navigation radios.