Electricity resulting from the application of mechanical pressure on certain crystals like quartz and tourmaline is called piezoelectricity.
When these crystals are subjected to mechanical strain, a voltage across their opposite faces.
Conversely when a voltage is applied to such crystals, they vibrate.
Piezoelectric materials are used for converting mechanical strain into an electrical signal in such devices as microphones and phonograph pick-ups. The converse effect in which a mechanical output is derived from an electrical signal output is used in such devices as headphones and quartz watches.
The phenomenon of piezoelectricity was discovered in the 1880s.
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