Definition
An electronic component whose electrical resistance changes with the amount of light falling on it. In darkness its resistance is high, blocking current flow; in bright light its resistance drops, allowing current to flow more freely. Used in circuits that need to sense light levels.
Plain English
A small part in an electrical circuit that lets more electricity pass through it when light shines on it, and less when it's dark. It works like a light-controlled switch.
Context Anchor
Seen in aircraft electrical and instrument-lighting discussions, especially in circuits that respond automatically to cockpit or outside light.
Derivation
From 'photo' (Greek 'phos', meaning light) and 'resistor' (a component that resists the flow of electricity). Together: a resistor controlled by light.
Why Pilots Care
Photoresistors are part of how cockpit lighting and exterior light systems automatically respond to changing conditions. When an automatic dimming circuit fails or behaves oddly, a faulty photoresistor is often the cause.
Intuition Check
A photoresistor does not take pictures. Here, photo means light: it is a resistor controlled by light falling on it.
Example Sentence 1
The instrument panel's automatic dimming circuit uses a photoresistor to sense cabin light levels and adjust display brightness accordingly.
Example Sentence 2
During preflight checks the mechanic verified that the photoresistor responded to a flashlight before reinstalling the instrument panel.