Both alternators and generators can produce energy, but they are produced in different ways, and it may be difficult to identify the difference.
Most people consider generators to be used as backup power sources at home or in recreational vehicles, as well as alternators with equipment to charge car batteries.
While this distinction is more or less true, there are significant technological differences in the way these devices produce energy for our cars and houses.
Key Takeaways
- Alternators produce alternating current (A.C.), while generators produce either direct current (D.C.) or A.C.
- Alternators are more commonly used in automobiles, whereas generators are utilized for standalone power generation.
- Alternators are more efficient and lighter than generators, making them more suitable for certain applications.
Alternator vs Generator
An alternator converts mechanical energy into AC electrical energy, while a generator converts mechanical energy to either AC or DC electrical energy. An alternator always induces an alternating current, while a generator generates either alternating or direct current. Alternators are smaller in size compared to Generators.

A mechanical device that transforms mechanical energy into AC electrical energy is known as an alternator. The magnetic field (rotor) revolves around the armature in this kind of generator (stator).
Using a DC source, a permanent magnet or an electromagnet generates a magnetic field. The armature is surrounded by an electromagnet in a housing (conductor windings).
However, in the case of a generator, the armature is at the rotor, and the field winding is at the stator.
A generator is a machine that transforms mechanical energy into either AC or DC electrical energy.
The stator, the outer casing that surrounds the armature of the generator, is composed of either a permanent magnet or a fixed electromagnet.
Inside this fixed magnetic field, the armature is made up of conductor coils that spin around their axis. The magnetic field line crossing the conductors fluctuates due to the spinning armature.
As a result, the spinning armature generates a current.
Comparison Table
Parameters of Comparison | Alternator | Generator |
---|---|---|
Definition | An alternator is a machine that transforms mechanical energy into alternating current (AC) electricity. | A generator is a mechanical device that transforms mechanical energy into electrical energy, either AC or DC. |
Output Current | An alternator produces an alternating current at all times. | Alternating or direct current may be generated by a generator. |
Efficiency | Very Efficient. | Less Efficient. |
Magnetic Field | An alternator’s stator contains a spinning magnetic field. | The magnetic field is stationary or fixed where the armature winding rotates in the case of a generator. |
Output | High | Low |
What is an Alternator?
In the electric power industry, an asynchronous generator (also known as an alternator) is a machine that transforms mechanical energy from a primary mover into alternating current at a certain voltage and frequency.
The numerous advantages of three-phase alternators make them a popular choice for use in distribution, generating, and transmission applications.
Large alternators are used to generate large amounts of electricity in thermal, hydroelectric, and nuclear power facilities. The magnetic pole of the rotor is excited by the direct field current flowing through it.
As the rotor rotates, the magnetic flux cuts the conductor of the stator, resulting in the generation of EMF.
An EMF and current are produced in the armature conductor as the magnetic poles alternately spin in the N and S directions. The armature conductor rotates first clockwise and then anti-clockwise.
This causes the alternating current to be produced as a consequence.

What is a Generator?
The generator is responsible for converting mechanical energy into electrical energy, also known as power.
The functioning of the generator is based on the concept of Faraday laws of electromagnetic induction, which states that anytime the conductors cut the magnetic flux EMF induces, the generator stops working.
Even though the conductor is closed, this EMF causes the current to flow. Generators are composed of two basic components: the magnetic field and conductors.
An axially rotating rectangular revolving coil is used in the generator, and it rotates in the magnetic field around its axis. Either a permanent magnet or an electromagnet is used to create the magnetic field in the room.
Two slip rings are used to connect the coil’s ends together. During the operation of the slip ring, the current generated in the coil is collected and transferred to the external load resistor R.
The rotating coil is called the armature, and it is made of copper. They can even recharge depleted batteries.
When the rotor is linked to the commutator, the direct current supplied by the generator is created.
The commutator is a key component in a generator’s direct current generation; it is made up of a series of independent rings that connect the generator to an external circuit in such a manner that the current generated is DC.

Main Differences Between an Alternator and a Generator
- An alternator is a device that transforms mechanical energy into alternating current (AC) electricity, whereas a generator is a mechanical device that transforms mechanical energy into electrical energy, either AC or DC
- An alternator produces an alternating current at all times, whereas a generator may generate alternating or direct current.
- The alternator is very efficient, whereas the generator is not much efficient
- The stator of an alternator includes a rotating magnetic field. In the case of a generator, the magnetic field is stationary or fixed where the armature winding spins.
- Alternators produce more energy than generators. When compared to an alternator, generators have a lesser output.
