Electric motor

An electric motor is a machine that converts electrical energy into mechanical motion, the reverse of what a generator or dynamo does. In many designs the two devices differ only in their application and minor construction details, which is why the traction motors on locomotives can also act as generators when the locomotive uses dynamic braking. Most motors work by electromagnetism, using the force on a current-carrying conductor in a magnetic field, though electrostatic and piezoelectric motors also exist. A rotary motor has a rotor and a stator, and the main families are direct current motors, universal motors that run on either supply, alternating current induction and synchronous motors, stepper motors, brushless motors and linear motors. Michael Faraday built an early rotary demonstration in 1821, Thomas Davenport drove a toy train with one in 1834, Zenobe Gramme produced the first industrially useful machine in 1873, and Nikola Tesla and Galileo Ferraris developed the rotating magnetic field principle for alternating current motors in the 1880s. For transport the electric motor matters as the traction unit of railways, trams and electric vehicles.