Definition
A temperature-sensing element made of two different metals bonded together along their length. Because the two metals expand and contract at different rates as temperature changes, the strip bends predictably with heating or cooling. This bending motion is used to operate switches, gauges, or thermostats.
Plain English
Two thin layers of different metals stuck together. When heated or cooled, one side grows or shrinks more than the other, so the strip curls. That curling movement can flip a switch or move a needle on a gauge.
Context Anchor
Seen in aircraft powerplant temperature indicators, heat-operated switches, and warning devices that respond to rising or falling temperature.
Derivation
From Latin bi- (two) and Greek metallon (metal). The name simply describes the construction: two metals joined as one strip. Knowing this reminds you that the whole device works because the two metals behave differently when heated.
Why Pilots Care
Many cockpit temperature indications and warning systems rely on bimetallic elements. If a temperature gauge or warning light behaves oddly, the sensing element itself may be the cause rather than the actual engine condition.
Grounding Statement
When the strip gets hotter, one metal layer grows slightly more than the other, so the joined strip bends instead of staying straight.
Intuition Check
A bimetallic strip is not just any strip of metal, and it is not two loose pieces. The two different metals must be bonded together so their unequal reaction to heat makes the strip bend.
Example Sentence 1
The cylinder head temperature gauge uses a bimetallic strip that bends as the engine heats up, moving the indicator needle.
Example Sentence 2
Heat from the engine caused the bimetallic strip to bend and close the circuit that turns on the over-temperature warning light.