How Spark Plugs Works?

A spark plug is a electrical device used in an internal combustion engine that is, an engine that derives its power via exploding gases inside a combustion chamber to ignite the air-fuel mixture.It contains an artificial bolt of lightning within the combustion chamber (cylinder head) of the engine. The electrical power means voltage is transmitted to spark plug in  order to create a spark and to “light the fire” within the controlled chaos of the combustion chamber.
Here, the voltage at the spark plug can be anywhere from 20,000 to more than 100,000 volts.Spark plugs have an insulated center electrode which is connected by a heavily insulated wire to an ignition coil or magneto circuit on the outside, forming, with a grounded terminal on the base of the plug, a spark gap inside the cylinder.

 In modern engines for Standard spark plugs contain  a copper centre electrode core which is surrounded by a nickel alloy, which are clearly visible at the tip of the plug. Where as in case of inside the plug, the centre electrode is encased in porcelain, which helps transfer heat from the engine to the cooling system. Premium spark plugs make use of precious metals, like platinum or iridium, in place of the nickel alloy. These metals have higher melting points -- and higher prices to match.

Cars typically have four-stroke gasoline engines, which means there are four strokes, or movements, to the moving parts inside the engine per rotation. Inside each cylinder is a piston, which moves up and down within the cylinder to compress the gas for combustion, and pushes the exhaust gases out after combustion.

The piston is operated by an arm that attaches to the crankshaft, a shaft that extends through the bottom of the engine. The piston goes up and down twice during each rotation, hence the four strokes -- up, down, up, down.

The spark plug is positioned at the top of the cylinder, where the air-fuel ratio is compressed. The tip of the plug sits inside the engine, recessed into the side of the cylinder wall. The other end remains outside the engine and is attached to a wire that is also attached to the distributor.

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