Definition
A type of rechargeable electrochemical cell that uses cadmium as one of its electrode materials, most commonly in nickel-cadmium (NiCad) aircraft batteries. Each cell produces a nominal voltage of about 1.2 volts, and multiple cells are connected in series to form the battery used to start engines and power electrical systems.
Plain English
It is one of the small individual battery units inside an aircraft's nickel-cadmium battery. Several of these cells are wired together to make up the full battery.
Context Anchor
Seen in aircraft electrical and instrument-system discussions, especially where equipment uses light sensing or automatic control based on light level.
Derivation
Cadmium is a soft metallic element discovered in 1817, named from the Latin cadmia (a zinc ore in which it was first found). A 'cell' in electrical terms comes from the Latin cella, meaning a small chamber or compartment — fitting, because each cell is a self-contained chamber that produces electricity through a chemical reaction.
Why Pilots Care
It provides a known, unchanging voltage reference that lets technicians confirm instruments and regulators are reading correctly before flight.
Analogy
Think of it like an automatic night-light sensor. The part does not see the way a person sees; it simply changes its electrical behavior when the light level changes.
Intuition Check
Do not assume cell means a battery here. In this term, a cell is a small light-sensitive part in an electrical circuit.
Example Sentence 1
The aircraft's NiCad battery is made up of twenty cadmium cells connected in series to produce 24 volts.
Example Sentence 2
Using the cadmium cell as a reference, the shop calibrated the sensitive altimeter to ensure accurate altitude readings.