How works a dial thermometer? It has a long probe and a circular dial.?
Answer:
It uses a bimetallic strip twisted into a circle. Two mismatched metals (one with high coefficient of thermal expansion and the other with a low one) are stuck together. When it gets hotter the big expansion coefficient part gets longer but is held back by the low coefficient one. That makes the whole combined strip twist around more. Since the thermometer pointer is attached to the end of that strip it is turned to point to a different number on the temperature scale.
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