Alternators and generators are two devices which generate electricity. An alternator can be called a type of generator. Although both these devices serve the same function, they are quite different in every other aspect.

An alternator is a charging system for cars that produces electricity. Generators are used in the production of large-scale electricity. Both alternators and generators convert mechanical energy into electrical energy. The main difference between them is in regard to what spins and what is fixed.

In an alternator, electricity is produced when a magnetic field spins inside the stator (windings of wire). In a generator, on the other hand, the armature or windings of wire spin inside a fixed magnetic field to generate electricity.

Alternators are considered more efficient than generators. Alternators conserve energy by using only the energy that is needed, while generators use all the energy that is produced. Alternators have a higher output than generators. When it comes to polarization, alternators and generators are very different. While generators have to be polarized after installation, there is no need for polarization in alternators.

Alternator brushes last longer than those of generators. This is because the brushes in an alternator are used only for carrying current to power the rotor and the slip rings they ride are smooth.

There is another difference between generators and alternators when it comes to charging. An alternator will not charge a dead battery and if you do try to charge it, there is a possibility that it will burn out. A generator, however, can be used for charging a dead battery.

There is also a difference in size as alternators can fit into a small space, while generators are larger.