Electric motors and machines

An electric motor is a machine that converts electrical energy into mechanical motion, almost always rotation. Its operation rests on the interaction between magnetic fields and electric currents: a current-carrying conductor placed in a magnetic field experiences a force, and by arranging conductors on a rotor inside a stationary magnetic structure, that force is turned into continuous torque. The same physical principles run in reverse in a generator, which produces electricity when its shaft is driven mechanically, so motors and generators are closely related machines.

Motors are broadly divided by the type of supply they use. DC motors run on direct current and have long been valued for the ease with which their speed can be controlled. Traditional brushed DC motors use a commutator and brushes to switch current in the rotor windings, while brushless DC motors replace this mechanical switching with electronic control, improving reliability and efficiency. AC motors run on alternating current; induction motors in particular are rugged and widely used in industry because they need no electrical connection to the rotor.

Beyond these basic families lie machines tailored to specific tasks. Servo motors, available in both brushed DC and brushless AC forms, are designed for precise control of position, speed and torque in robotics and automation. Linear motors produce straight-line motion directly rather than rotation. Choosing a motor involves balancing torque, speed range, efficiency, controllability and cost against the demands of the application.

Frequently asked questions

How does an electric motor produce motion?

A current flowing through conductors in a magnetic field experiences a force. Arranging these conductors on a rotor inside a magnetic field converts that force into continuous rotational torque.

What is the difference between a brushed and brushless DC motor?

A brushed motor uses physical brushes and a commutator to switch current in the windings, whereas a brushless motor uses electronic switching, which improves reliability and reduces wear.

Why are induction motors so common in industry?

Induction motors are simple, robust and inexpensive, and they require no electrical contact to the rotor, which makes them low-maintenance and well suited to continuous duty.