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spark plug
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spark plug automobile electrical system internal-combustion engine: four-stroke cycle gasoline engine V-type engine Wankel rotary engine
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spark plug
spark plug

spark plug

electronic device
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Also known as: sparking plug
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Also called:
Sparking Plug
Key People:
Robert Bosch

spark plug, device that fits into the cylinder head of an internal-combustion engine and carries two electrodes separated by an air gap, across which current from a high-tension ignition system discharges, to form a spark for igniting the air–fuel mixture. The electrodes must be able to resist high temperatures, and the insulator separating them must withstand high temperatures and also an electric stress up to several thousand volts. Spark-gap length affects the energy of the spark, and the shape of the insulator affects the temperature of operation. When too cool, operation leads to carbonization and short-circuiting of the gap; when too hot, there may be preignition.

This article was most recently revised and updated by Amy Tikkanen.