Difference Between Alternator and Generator

Main Difference – Alternator vs. Generator

Alternators and generators convert mechanical energy into electrical energy. The main difference between alternator and generator is that a generator is any device that converts mechanical energy into electrical energy (in the form of alternating current or direct current), whereas an alternator is a type of generator that produces alternating current.

What is a Generator

A generator is a device which converts mechanical energy into electrical energy. A generator can produce AC current or DC current. Typically in generators, there are coils of wires forming a rotor. The rotor sits inside a magnetic field formed by stationary magnets. Mechanical energy is used to rotate the rotor. Now, because the wires are constantly moving, the magnetic flux across the wires are changing. According to Faraday’s law, this induces a current in the wires. Per each half-cycle of the rotor, the direction of current induced on it changes. Therefore, this produces an alternating current in the wire. If the external circuit requires an alternating current, the generator could be directly connected to the external circuit. A DC current can be produced by attaching the rotor to a commutator. A commutator is made of a set of split rings, that connect the generator to the external circuit in such a way that the current sent into the external circuit is always a direct current.

Difference Between Alternator and Generator - A_DC_Generator

A DC generator: The coils of wire rotate in the static magnetic field created by the magnets. The commutator is shown in gold.

What is an Alternator

An alternator is a type of generator that converts mechanical into electrical energy in the form of an alternating current. Typically, in devices called alternators the wires are stationary and mechanical energy is used to rotate a magnet. The result is the same as earlier: there is a changing magnetic flux across a conductor, and so a current is produced. As before, the current produced is an alternating one. Alternators give out this current as it is, without converting it into DC current.

Difference Between Alternator and Generator - An_alternator

A simple alternator: here, the magnet forms the rotor, while the coil forms the stator (it does not move)

Difference Between Alternator and Generator

Alternators are technically a type of AC generators. However, the term “AC generator” is often reserved for devices where the magnets are stationary. If the magnets rotate, the device may be called an “alternator”. This is not a strict distinction: the usage of these terms may vary between different disciplines.

Type of Current Produced

Generators produce AC or DC current.

Alternators produce only DC current.


In generators, typically the coils form the rotating parts (rotor), while the magnets form the stationary parts (stator).

In alternators, typically the magnets form the rotor while the coils of wire form the stator.


Alternators use slip rings and so the brushes in alternators tend to last longer compared to those in generators.


Image Courtesy:

“Illustration of a simple electric motor” by Wapcaplet (Own work) [CC BY-SA 3.0], via Wikimedia Commons

“Diagram of an alternator, showing the rotating magnet (the Rotor) and the stationary wire winding (the Stator)…” by Egmason (User:J JMesserly modification of original svg by User:SiriusA) [CC BY 3.0], via Wikimedia Commons

About the Author: Nipun