Which is one of the four strokes in an internal combustion engine?

• A. Power stroke
• B. Exhaust stroke
• C. Intake stroke
• D. Compression stroke

Answer: (A)

In a four-stroke engine, the cycle is divided into four distinct actions: intake, compression, power, and exhaust. The power stroke is the moment when the combustion of the air–fuel mixture creates high pressure that pushes the piston downward. This downward push is what provides the actual work, turning the piston’s motion into rotational motion of the crankshaft. After the mixture is compressed, ignition occurs (in a gasoline engine), and the resulting explosion drives the piston down during the power stroke. The other strokes play supporting roles: intake brings in the air-fuel charge, compression increases its pressure, and exhaust removes the burnt gases. So naming the power stroke identifies one of the four essential stages of the engine’s operating cycle.