Spark Plug

A spark plug is a device that delivers an electric current from an engine's ignition system into its combustion chamber, producing a spark that ignites the compressed fuel and air mixture while sealing the chamber against the pressure of combustion; it consists of a metal threaded shell screwed into the cylinder head, a central electrode insulated from the shell by ceramic, and one or more gaps across which the spark jumps. Étienne Lenoir is generally credited with inventing the spark plug for use in his 1860 gas engine, the first internal combustion piston engine, and Gottlob Honold, working for Robert Bosch, invented the first commercially viable high-voltage spark plug in 1902.