What is a single device that converts a source of energy into mechanical motion called?

A single device that converts a source of energy into mechanical motion is referred to as a prime mover. This term is commonly used to describe equipment like steam turbines, internal combustion engines, and water turbines, which take in energy (in the form of steam, fuel, or kinetic energy from water, respectively) and convert it into mechanical energy.

Prime movers are essential in various applications, as they facilitate the conversion of energy types for useful mechanical work, such as driving generators or other machinery. Understanding the role of a prime mover is crucial for power engineering, where the conversion of energy into motion is a fundamental process in the operation of systems like generators and pumps.

In contrast, while motors also convert electrical energy into mechanical motion, they are typically electrical devices specifically designed for that purpose. A generator is focused on converting mechanical motion into electrical energy, thus operating in the reverse of the function described. A piston is an internal component of engines and other devices but does not perform the overall conversion from energy to mechanical motion by itself.