What is "spark plug"

Spark plug \Spark plug\ In internal-combustion engines with electric ignition, a plug, screwed into the cylinder head, connected with the induction coil or magneto circuit on the outside, and used to produce a spark to ignite the fuel-air mixture in the engine.

n. The part of an internal combustion engine which forms a high-voltage electric spark which ignites the fuel-air mixture to begin the power stroke.

n. electrical device that fits into the cylinder head of an internal-combustion engine and ignites the gas by means of an electric spark [syn: sparking plug, plug]

A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine. A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. The central electrode, which may contain a resistor, is connected by a heavily insulated wire to the output terminal of an ignition coil or magneto. The spark plug's metal shell is screwed into the engine's cylinder head and thus electrically grounded. The central electrode protrudes through the porcelain insulator into the combustion chamber, forming one or more spark gaps between the inner end of the central electrode and usually one or more protuberances or structures attached to the inner end of the threaded shell and designated the side, earth, or ground electrode(s).

Spark plugs may also be used for other purposes; in Saab Direct Ignition when they are not firing, spark plugs are used to measure ionization in the cylinders – this ionic current measurement is used to replace the ordinary cam phase sensor, knock sensor and misfire measurement function. Spark plugs may also be used in other applications such as furnaces wherein a combustible fuel/air mixture must be ignited. In this case, they are sometimes referred to as flame igniters.

Spark plug may refer to:

• Spark plug, an electrical device in some internal combustion engines and ignites fuel by means of an electric spark
• Spark plug, a rod of uranium or plutonium in a hydrogen bomb used to heat the fusion fuel to the point of nuclear fusion
• Spark Plug, Barney Google's race horse from the Barney Google and Snuffy Smith comic strip
• Spark Plug (album), a 1971 album by jazz soul guitarist Melvin Sparks
• "Spark Plug", a song by Stereolab from their 1996 album Emperor Tomato Ketchup
• "Spark Plug", a song by Idiot Pilot from their 2005 album Strange We Should Meet Here

Sparkplug may also refer to:

• Sparkplug Witwicky, a Transformers G1 human character
• Sparkplug (Transformers), the Mini-Con partner of Optimus Prime
• Sparkplug, the car in the animation series The Houndcats
• Sparkplug lighthouse, a type of lighthouse named for its shape.

Spark Plug is the second album by soul jazz guitarist Melvin Sparks which was recorded for the Prestige label in 1971.