How do machines change energy into motion?

Machines change energy into motion by acting as intermediaries that transform various forms of energy—such as chemical, thermal, or electrical—into mechanical energy. This process is fundamental to the operation of prime movers, which extract energy from natural sources like fuel or moving fluids to produce useful output, typically in the form of rotating shafts.1

The specific mechanism of this transformation depends on the type of machine:

• Internal-Combustion Engines: These devices convert the heat released during combustion into mechanical work. Hot, expanding gases exert force against moving surfaces, such as a piston or turbine blade, creating motion.2
• Electric Motors: These convert electrical energy into mechanical energy by utilizing electromagnetic phenomena. By passing current through conductors within a magnetic field, the motor generates torque, resulting in rotary motion.3
• Mechanical Linkages: Once energy is converted into motion, a machine’s mechanism uses interconnected parts—such as connecting rods and crankshafts—to modify that motion, for example, by changing rectilinear motion into rotary motion.4

Ultimately, all machines perform a motion-modifying function, as they must move to accomplish physical tasks.41