Inside a gasoline engine
A simplified four-stroke engine turns fuel energy into a turning shaft.

Picture in words: 1. Intake: A piston moves down while air and fuel enter the cylinder.
2. Compression: The piston moves up and squeezes the mixture.
3. Power: A spark starts combustion. Expanding hot gases push the piston down and turn a crankshaft.
4. Exhaust: The piston moves up and pushes exhaust gases out. The cycle repeats.

One more wonder: An electric motor does not use this fuel-burning cycle.
This is a learning diagram, not an engine-building activity. Real engines are hot and have moving parts.

Question: What pushes the piston during the power stroke?
Answer: Expanding hot gases

Sources:
US Department of Energy: engine basics — https://www.energy.gov/cmei/vehicles/articles/internal-combustion-engine-basics

Reviewed 28 September 2026. Simplified educational illustration, not to scale.
https://atherverse.com/kids/how-things-work/engines/