Motor

A motor is a device that converts a form of energy into mechanical motion. The input energy can be fuel, electricity, or steam. The most common output is rotation, which transmits power through a rotating shaft or wheel.

Motors are fundamental to vehicles, factories, and electrical systems. Performance is assessed by power output, torque, rotational speed, and efficiency—the ratio of useful energy output to energy input. Some energy is always lost as heat and friction.

Main types

Internal combustion motors burn fuel inside cylinders, including petrol and diesel engines. External combustion motors, such as steam engines, burn fuel outside the working chamber. Electric motors use magnetic fields to convert electricity into rotation. Gas turbines power most aircraft.

How an internal combustion engine works

A typical internal combustion engine operates in cycles. Air and fuel are drawn into a cylinder, then compressed, ignited, and burned. The expanding gases push a piston outward, and the exhaust is expelled. The linear motion of the piston is converted into rotational motion by the crankshaft.

Brief history

Steam engines powered factories and trains in the 18th and 19th centuries. Internal combustion engines emerged in the late 19th century and enabled the automobile. In the 20th century, gas turbines revolutionized aviation. Recently, electric motors and batteries have re-entered the automotive sector.