Which type of engine operates on a back-and-forth motion of its internal parts?

The reciprocating engine operates on a back-and-forth motion of its internal parts, specifically the pistons. In this type of engine, fuel and air are drawn into a cylinder, where the piston moves down to create a vacuum, drawing in the mixture. The mixture is then compressed by the piston moving back up, ignited by a spark plug, and the rapid expansion of gases pushes the piston back down. This continuous cycle of movement is fundamental to how reciprocating engines generate power, such as in many cars and small aircraft.

In contrast, other types of engines mentioned do not utilize this back-and-forth motion. For instance, rotary engines use a different mechanism where the motion is more circular and does not involve reciprocating components. Jet engines rely on a continuous flow of air and combustion, producing thrust through the expulsion of exhaust gases rather than reciprocating motion. Electric engines convert electrical energy into mechanical energy through rotary motion, not the back-and-forth movement characteristic of reciprocating engines.