What is Homopolar Motor – The Ultimate Guide

A homopolar motor is a unique electromechanical device with very distinct performance properties. From history, working principle, classification to applications – this guide covers all critical information about homopolar electric motors.

Let’s dive right in.

Basics of Homopolar Explained

The homopolar motor is an electric motor that is comprised of a magnet, a source of current and a conductor. The conductor is placed at a right angle to the magnetic field produced by the magnet. Current is then passed through the conductor and a resulting force will make the conductor to move at a continuous motion.

Usually, this take place in one specific direction depending on the direction of current and direction of the magnetic field.

Homopolar Motor
Homopolar Motor

History of the Homopolar Motor.

Electromagnetism was discovered by Hans Christian Oersted a chemist and physicist. In 1821 Humphry Davy and William Hyde Wollaston a scientist from Britain tried to build the first ever electric motor but failed.

Later that same year,Michael Faraday  made the first ever functioning electric motor and was demonstrated at the royal institution of London which was later known as the homopolar motor.

Benefits of Homopolar Electric Motors

The homopolar electric motor has a simple and easy to understand and build the structure. It is made-up of a simple battery a magnet and a conductor.

Due to the simplicity of the structure, this makes the motor suitable for teaching the working principles of a motor.

The motor can produce low rotational speeds with a high rotational force. This can be effective in some heavy machinery.

Disadvantages of Homopolar Motors

The main disadvantage is that there is inefficiency of motor speed. This is due to the single path movement of electric current and need of high amount of current. Which results in wastage of energy in form of heat.

Basic Homopolar Motor Features

The homopolar motor has important features that are listed below;-

  • A source of DC current such as a battery.
  • A magnet with two poles, north and South Pole.
  • A conductor of current such as a copper wire.

Types of Homopolar Electric Motor

Generally, we can classify these homopolar electric motor systems as:

Brushless Homopolar Motor

This is a homopolar motor that does not require brushes, conductors or electronics but only needs the direct current and the magnetic field to produce torque

Brushless Homopolar Motor
Brushless Homopolar Motor

Battery Homopolar Motor

This is a homopolar motor that uses a direct current created by a battery and a magnetic field produced by a magnet. A conductor is the connected at both ends of the battery ensuring that the magnetic field is perpendicular to the conductor. This will automatically cause the conductor to spin in a circular motion.

Battery Homopolar Motor
Battery Homopolar Motor

How to DIY Homopolar Motor Designs

To make a simple homopolar motor, you need a battery as a source of current, a magnet and a conductor for instance a copper wire. Place the battery with the magnet at the bottom.

Connect the copper wire from the positive terminal to the negative terminal maintaining a close distance to the magnet. This will automatically cause the movement of the copper wire in a circular motion.

Here are more magnetic DIY ideas in the market today.

How Homopolar Motor Works


The motor works as a result of a force produced when current is passed perpendicular to a magnetic field.

There is usually a strong magnet at the bottom of the motor, a battery is then placed at the top of the magnet and a conductor running from end to end of the battery.

When current is passed through the conductor that is placed perpendicular to the magnetic field, a resulting force is produced.

This force is produced when the two opposite magnetic fields get into contact, the field produced by the conductor carrying electricity and the magnetic field produced by the magnet. As a result, this causes the conductor to move at a constant circular motion.

Homopolar Motor Working Principle
Homopolar Motor Working Principle

Efficiency of Homopolar Electric Motor

Efficiency of the motor depends on various factors, some of which are as follows;-

  • To increase the speed of movement, one has to increase the strength of magnetic field produced by the magnet. This could be done by increasing the number of magnets used or using a much stronger magnet.
  • An increase in strength of current produced will also result in faster and much more efficient movement in conductor rotation. This will result in an increase in strength of magnetic field formed around the conductor.
  • Reducing the distance between the conductor and the magnet will also increase the speed of motor movement. Comparing a motor with conductor far away from the magnet and that that is closer, the closest one will spin the fastest.

Homopolar Motor Uses

  • Used in applications that are cost effective such as making of toys and for scientific demonstrations.
  • Can be used in some heavy machinery due to their high torque produce and low speed.


The homopolar motor is a direct current electric motor that is comprised of a magnet, a source of current and a conductor.

The motor is simple enough to help in demonstrating the basic functioning of an electric motor. Homopolar motor can produce low rotational speeds with a high rotational force which can be effective in some heavy machinery.

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