How Does an Electric Motor Work?

How Does an Electric Motor Work

An electric motor converts electrical energy into mechanical motion. It typically operates on the principles of electromagnetism, wherein a current-carrying conductor produces a magnetic field, resulting in motion.

Basic Principles of Electromagnetism

Understanding Magnetic Fields

Magnetic fields are invisible areas around magnets where magnetic forces are exerted. These fields have both a direction and magnitude, and they are created by moving electric charges.

How Does an Electric Motor Work

Origin of Magnetic Fields

All magnetic fields originate from moving electric charges. In everyday materials, these charges are often the electrons moving within atoms. When these electrons move in a coordinated manner, they generate a more substantial magnetic field. For instance, iron atoms have certain properties that allow them to generate a significant magnetic field when aligned.

Representation with Field Lines

Magnetic field lines are used to depict the strength and direction of a magnetic field. They emerge from the north pole of a magnet and re-enter at the south pole. The closer these lines are, the stronger the magnetic field in that region. Field lines provide a visual representation, aiding in understanding the behavior of magnets and charged particles in the field.

Interaction with Charged Particles

When charged particles, like electrons or protons, move through a magnetic field, they experience a force. This force can cause the charged particle to move in a circular or helical path, depending on the angle at which it enters the magnetic field. This phenomenon is fundamental in devices like cyclotrons used in particle physics.

The Concept of Electromagnetic Induction

Electromagnetic induction refers to the process by which a change in a magnetic field can induce an electric current in a conductor. It is the fundamental principle behind many electrical devices, including transformers and electric generators.

Faraday’s Law of Induction

Michael Faraday discovered that a change in the magnetic environment of a loop of wire induces a voltage in the wire. The amount of induced voltage is directly proportional to the rate of change of the magnetic flux. This discovery led to the formulation of Faraday’s Law, which states that the induced electromotive force (EMF) in any closed circuit is equal to the negative rate of change of the magnetic flux through the circuit.

Electric Motor

Applications of Electromagnetic Induction

The principle of electromagnetic induction has numerous applications. For instance, generators convert mechanical energy into electrical energy using this concept. When a coil rotates in a magnetic field, an alternating current is induced, which can then be used to power electrical devices. Similarly, transformers use electromagnetic induction to increase or decrease the voltage of alternating current.

Lenz’s Law

Another crucial aspect of electromagnetic induction is Lenz’s Law. It states that the direction of the induced current (and EMF) is such that it opposes the change in magnetic flux that produced it. This law is a manifestation of the conservation of energy in electromagnetic systems.

Main Components of an Electric Motor


The rotor is the rotating part of an electric motor, which turns in response to the force derived from the interaction between its own magnetic field and the magnetic field of the stator.

Types of Rotors

There are mainly two types of rotors:

  • Squirrel Cage Rotor: This type comprises aluminum or copper bars set into grooves and connected at both ends. It is robust and requires minimal maintenance.
  • Wound Rotor: In this kind, windings are placed on the rotor which are connected to external circuits through slip rings and brushes.


The stator acts as the stationary part of an electric motor. It typically contains the motor’s windings and can have either a set of coils that generate a rotating magnetic field or a set of permanent magnets.

Function of the Stator

The stator generates a rotating magnetic field when an AC current passes through its windings. This magnetic field induces a force on the rotor, causing it to turn.


A commutator is a rotary switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit.

How a motor works

Working Principle of Commutator

As the rotor turns, the commutator maintains the direction of the current flowing through the rotor windings so that the rotor continues to turn in the same direction. In simple terms, it ensures that the torque generated by the rotor remains consistent and in the desired direction.


Brushes play a role in transmitting electrical current between static wires and moving parts in a motor or generator.

Composition and Role of Brushes

Typically made of carbon, brushes are designed to be wear-resistant and to maintain a consistent electrical contact with the commutator. As the commutator rotates, the brushes slide over its surface, allowing the current to flow into the rotor windings.


Windings are coils of wire that are wrapped around the core of both the stator and rotor.

Purpose of Windings

When an electric current flows through these coils, they produce a magnetic field. In the stator, the windings generate a rotating magnetic field that drives the rotor. On the other hand, in certain types of motors, the rotor’s windings are energized by the commutator, allowing it to produce its own magnetic field which interacts with the stator’s field to generate motion.

Types of Electric Motors

Direct Current (DC) Motors

DC motors convert direct current electrical energy into mechanical energy. They are versatile and offer high torque at low speeds.


Brushed DC Motors

Brushed DC motors use brushes to conduct current and power the rotor. These brushes work in tandem with a commutator to ensure the rotor spins in the desired direction. One of the notable features of brushed motors is their simplicity and reliability. However, over time, brushes can wear out and require replacement. Common applications of brushed DC motors include toys, tools, and many household appliances.

Brushless DC Motors

In contrast to their brushed counterparts, brushless DC motors don’t rely on brushes for current conduction. Instead, they use electronic controllers to switch the phase to the motor windings and keep the rotor moving. Brushless motors offer higher efficiency and require less maintenance because there’s no brush wear. They are becoming increasingly popular in high-performance applications like drones, computer hard drives, and electric vehicles.

Alternating Current (AC) Motors

AC motors are electric motors driven by alternating current. Unlike DC motors, the electric current in an AC motor changes direction periodically.

Synchronous AC Motors

Synchronous motors rotate precisely at the supply frequency or a submultiple, making their rotation synchronized with the frequency of the supply current. The speed remains constant, making these motors useful in applications where precise timing is crucial, like in clock systems or conveyor belts. They operate in synchronization with line frequency. To achieve synchronicity, these motors require an external source of direct current for initial excitation.

Induction AC Motors

Also known as asynchronous motors, induction motors are the most commonly used AC motors. Their operation relies on the principle of electromagnetic induction. When AC supply is given to the stator winding, it generates a rotating magnetic field. This rotating field induces a current in the rotor, which creates its own magnetic field. The interaction of these fields produces torque and causes the rotor to rotate. Due to their simplicity, ruggedness, and affordability, induction motors find applications in many industrial setups and household appliances.

Operational Mechanisms

The Role of the Commutator and Brushes

The commutator and brushes play a crucial role in the operation of many electric motors, ensuring that current flows in the desired direction to produce consistent torque.

How do electric motors work

Commutator Function

The commutator functions as a rotary switch. As the rotor spins, the commutator ensures that the direction of the current in the rotor windings remains consistent. This constant direction of current, combined with the rotating magnetic field produced by the stator, causes the rotor to turn in a single direction.

Brushes Function

Brushes maintain an electrical connection between the static part of the motor (the stator) and the rotating part (the rotor). Typically made of carbon, brushes slide against the rotating commutator to deliver current to the rotor windings.

Torque Production in Motors

Torque in electric motors originates from the interaction between the magnetic fields produced by the rotor and stator.

Magnetic Field Interaction

When the stator produces a magnetic field, it induces a current in the rotor. This current, in turn, creates its own magnetic field. The interaction of these two fields results in a force acting on the rotor, causing it to turn. The strength of the torque largely depends on the magnitude of the current flowing through the motor’s windings and the design of the motor itself.

Speed Control Methods

Controlling the speed of an electric motor is crucial for many applications. There are different methods to achieve this based on the type of motor and its intended use.

Voltage Control

For many DC motors, adjusting the voltage supplied to the motor controls its speed. Higher voltages increase the speed, while lower voltages decrease it. This method is common for smaller DC motors.

Frequency Control

For AC motors, particularly induction motors, the speed is directly related to the frequency of the AC supply. By varying this frequency using devices like Variable Frequency Drives (VFDs), one can precisely control the motor’s speed.

Pole Control

This method involves altering the number of magnetic poles in the stator of an AC motor. By changing the number of poles, the speed of the motor can be adjusted in distinct steps.

Torque Production in Motors

Applications of Electric Motors

Industrial Applications

Electric motors drive numerous industrial processes, proving integral to the productivity and efficiency of many sectors.

Manufacturing Machinery

In factories, electric motors power conveyor belts, which transport materials and finished products, ensuring smooth workflows. They also drive the machinery responsible for tasks like cutting, shaping, and assembly, enabling the consistent production of goods.

Pumps and Ventilation

Electric motors propel pumps that move liquids in various industries, from petrochemicals to food processing. Additionally, they drive ventilation systems, maintaining air quality and temperature in industrial settings.

Household Appliances

Almost every modern household uses appliances powered by electric motors, enhancing convenience and efficiency.

Washing Machines and Dryers

Electric motors in washing machines agitate and spin the drum, ensuring clothes get thoroughly cleaned. Similarly, in dryers, they rotate the drum, facilitating the even drying of clothes.

Refrigerators and Air Conditioners

In refrigerators, motors help in the circulation of cool air and the compressor’s operation. Meanwhile, in air conditioners, motors drive the fans that distribute cold air and assist the compressor in its cooling cycle.

Automotive Industry

The automotive sector has increasingly embraced electric motors, especially with the rise of electric vehicles (EVs).

Electric Motors construction

Electric Vehicles (EVs)

Electric motors provide the primary propulsion in EVs, offering quieter operation and instant torque compared to traditional internal combustion engines. With advancements in battery technology, EVs powered by electric motors are becoming a viable alternative to gasoline-powered vehicles. Check out the Electric Vehicle page on Wikipedia for more details.

Hybrid Systems

In hybrid vehicles, electric motors work in conjunction with gasoline engines, enhancing fuel efficiency and reducing emissions.

Renewable Energy Systems

As the world shifts towards sustainable energy sources, electric motors play an essential role in harnessing and converting renewable energy.

Wind Turbines

Electric motors, in a generator mode, convert kinetic energy from wind into electrical energy in wind turbines. The wind turns the blades, and the rotation drives the motor to generate electricity.

Hydroelectric Systems

Similarly, in hydroelectric power stations, flowing water turns turbines. The rotational energy from these turbines drives electric motors, converting it into electrical energy for distribution.

What roles do the commutator and brushes play in an electric motor?

The commutator and brushes are essential for the proper functioning of brushed electric motors. The commutator acts as a rotary switch, ensuring that the current direction remains consistent in the rotor windings. Meanwhile, brushes, typically made of carbon, maintain an electrical connection between the stator and the rotating rotor.

How is torque produced in electric motors?

Torque arises from the interaction of magnetic fields between the rotor and stator. The strength of the torque depends on the magnitude of the current flowing through the motor's windings and the motor's design.

What are the methods for controlling the speed of electric motors?

The speed of electric motors can be controlled through voltage control (for DC motors), frequency control (for AC motors), and pole control, wherein the number of magnetic poles in the stator is altered.

How do electric motors benefit the automotive industry?

Electric motors offer quieter operation, instant torque, and zero emissions in electric vehicles (EVs). Additionally, in hybrid vehicles, they enhance fuel efficiency and reduce emissions.

What role do electric motors play in renewable energy systems?

Electric motors convert kinetic energy into electrical energy in systems like wind turbines and hydroelectric power stations. They help harness and convert renewable energy efficiently.

What are the drawbacks of using brushed DC motors?

One main drawback of brushed DC motors is the wear and tear of brushes, which can lead to maintenance needs and reduced lifespan.

Are electric motors efficient?

Yes, electric motors are generally efficient, with many commercial motors achieving efficiencies over 90%. However, the exact efficiency can vary based on the design, size, and application of the motor.

How do electric motors compare in terms of cost and lifespan?

The cost and lifespan of electric motors vary depending on their type, size, and application. For example, brushless DC motors tend to have a longer lifespan and higher upfront cost compared to brushed DC motors. Generally, a well-maintained industrial electric motor can last over 15 years.

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