Difference Between Dynamo and Alternator

Electricity forms the most indispensable part of our life today. It provides us with lighting, entertainment, and a lot of things. It is impossible to imagine life without electricity.


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Earlier humans used batteries for electricity. But it was slowly found that batteries were not cost-effective or reliable. 

Modern homes are mostly powered by electricity. It is very convenient and can be produced in all kinds using anything from coal to oil to wind to waves. 

If we want to run anything either a television, a toaster, or an MP3 player we need a steady supply of electrical energy.

The basic law of physics “Conservation of Energy” explains how energy can be obtained as well as how we cannot get energy.

There is a fixed amount of energy in our universe and all we can do with this energy is to convert it into any useful form. Thus to convert energy and get a regular supply of electricity we require certain appliances.

 These appliances can be a generator, a motor, a dynamo, an alternator, etc. Here we will see how a dynamo and an alternator will function as well as differ.

Dynamo vs Alternator

The difference between Dynamo and Alternator is that a Dynamo generates a direct current that flows in one direction (that is it does not change directions) whereas an Alternator generates an alternating current that regularly changes its directions.

Dynamo vs Alternator

Comparison Table

Parameters of ComparisonDynamoAlternator
DefinitionDynamo is a machine that produces direct current flowing in the same directionAn alternator is a machine that produces alternating current flowing in different directions
Magnetic fieldStationaryRotating
Input supplyTakes input supply from rotorTakes input supply from stator
Energy efficiencyIt is less energy efficientIt is highly energy efficient
Range of Rotations Per Minute (RPM)Supports less range of RPMSupports wide range of RPM
Brush durabilityHas less brush durabilityHas high brush durability
Charging dead batteryCan be used to charge a dead batteryCannot be used to charge a dead battery
MaintenanceHas high maintenance chargesHas low maintenance charges

What is Dynamo?

Dynamo is an electrical device that produces direct current flowing in one direction. It is used for generating electrical energy. It basically converts mechanical energy into electrical energy.

The dynamo was first designed by Nikola Tesla. But the credit for conceptualizing the dynamo is given to Michael Faraday.

It was Faraday who first came up with the idea that a moving magnet in a closed electric circuit can induce electric current to flow.

The dynamo works on the concept of electromagnetic induction. When the coil linked with the magnetic field charges, an induced emf is set up in the coil.

The dynamo consists of several parts like yoke, poles, armature, stator, rotor, brushes, etc. The most essential parts of the dynamo are the stator and rotor.

The coils in the dynamo rotate through the magnetic field. Split ring commutators are used to connect to an external circuit.

This split ring commutator switches the connections at every half-turn thus keeping the current flowing in the same direction.

The brush ensures there is a continuous electrical connection without any inhibitions for the movement of the commutator.

There are two sets of brushes – one which taps the power to go to the main circuit and another set of brushes that take power from the armature to get the stator’s magnets powered. 

The armature holds on to a small amount of magnetism in its iron core.  When it begins to turn, a little bit of power is generated which excites the solenoids in the stator.

Slowly, the voltage rises and the dynamo gets to full power.

If a battery has to be prevented from getting overcharged then the output of the dynamo should be regulated. This is done by the regulator that changes the current as needed.

A Dynamo is quite expensive and big in size when compared to an alternator.  Dynamos are used to produce electrical power in automobiles, ships, trains, aircraft, etc.


What is an Alternator?

An alternator is a machine that produces an alternating current that constantly changes its direction. It converts mechanical energy into electrical energy. Alternators were created by Hippolyta Pixi a French inventor in 1832.

There are different types of alternators depending on their applications and design.

The alternator consists of two main components – Rotor and Stator. The rotating part is the rotor whereas the stator is the stationary part. 

The alternators work on the principle of electromagnetic induction, according to which to produce electricity a conductor, magnetic field, and mechanical energy is needed.

When the speed of the alternator is reduced or decreases then the output of the current also reduces or decreases. 

Also, the output of the current reduces or decreases when the temperature of the alternator increases. When the alternator runs on low speed the efficiency of the alternator automatically reduces. 

The brushes in the alternator provide power to the coil which is mounted on the rotating shaft. These brushes provide the direct current through two slip rings.

 The brushes of the alternator are quite durable and last longer when compared to that of the dynamo as the brushes only require enough electricity to get the rotor powered.

The alternator is used in the following applications:

  1. Automobiles
  2. Marine applications
  3. Radiofrequency transmission
  4. Diesel electrical multiple units
  5. Electrical power generator plants

The alternator is a cheap device which is light in weight. The construction of the alternator is simple and low in maintenance. The alternator is robust and more compact.

 But the alternator has advantages as well. It needs transformers to run and gets overheated when the current is high.


Main Differences Between Dynamo and Alternator

  1. The basic difference between Dynamo and Alternator is that Dynamo produces direct current which flows in one direction whereas Alternator produces an alternating current which changes its direction constantly.
  2. The magnetic field of the Dynamic is stationary whereas the magnetic field of the Alternator is rotating.
  3. The input supply taken by the Dynamo is through the rotor whereas the Alternator takes its input supply through the stator.
  4. The Dynamo has less energy efficiency when compared to the Alternator which has very high energy efficiency.
  5. The range of Rotations per Minute(RPM) of a Dynamo is less approximately <2000RPM whereas the RPM of Alternator will range from 6000RPM to 12,000RPM
  6. Dynamos have high maintenance costs whereas Alternator requires very little maintenance.
  7. The brushes of the Dynamo do not last long as split rings are used and get worn off quickly whereas the brushes of the Alternator last long as solid rings are used and do not get worn off easily.
  8. A Dynamo can be used to charge a dead battery whereas an Alternator cannot be used to charge a dead battery.
Difference Between Dynamo and Alternator


  1. https://link.springer.com/content/pdf/10.1007/978-1-349-06180-8_6.pdf
  2. https://link.springer.com/chapter/10.1007/978-1-349-03176-4_5
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