Wikipedia:POTD column/November 4, 2006

Animation showing the four-stroke cycle of an internal combustion engine, the most commonly used for automotive and industrial purposes today. The cycle is characterized by four strokes, or straight movements alternately, back and forth, of a piston inside a cylinder: (1) the intake stroke, (2) the compression stroke, (3) the power stroke, and (4) the exhaust stroke.

Animation credit: UtzOnBike
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