Build an Exciting Homopolar Motor!

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Is your child curious about what makes things go? If so, this is a great experiment to get them started! We’re going to be building a homopolar motor with just a few simple supplies.

What is a homopolar motor?

A homopolar motor is a simple electric motor that is powered by a single battery and a magnet. Unlike most motors, which use alternating current and multiple components, the homopolar motor uses direct current and only a few simple materials.

Ready to take this experiment for a spin? Let’s go!

How to make the Homopolar Motor technology experiment

Supplies you will need

For this experiment, you will need the following:

  • AA battery
  • Neodymium magnets (I used 4)
  • Copper wire (I used 18 gauge)
  • Scissors or wire cutters
Supplies needed for the Homopolar Motor technology experiment

Before you start

Only let your homopolar motor run for a few seconds at a time, otherwise, the wire may become too hot to handle.

Also, if you leave the wire too close to the battery or the magnets, it could cause too much friction for your wire to spin. Patience is key in this experiment!


Here is how to do this experiment with your toddler:

Step 1: Cut the copper wire

First, we’re going to cut about 4″ of copper wire.

If your copper wire has insulation, strip the insulation off of the ends with scissors, leaving about half an inch of exposed wire on each end.

Length of copper wire before cutting
Cut piece of copper wire, about 4-6 inches long

Step 2: Wrap the copper wire

If you want your copper wire to spin around the battery, find something a little larger than the AA battery and wrap it out a few times.

It’s important to find something slightly larger than the battery because, if the wire is too tight around it, it won’t spin.

I used my index finger and just adjusted where I needed it.

Wrapping the copper wire loosely around my finger
Testing to see if the wrapped wire is not too tight on the battery

I had a block of 4 magnets that I placed on the negative terminal of the battery.

When wrapping around the magnets (and the battery, for that matter), the copper wire needs to wrap around without being too tight on the magnets and battery. If it’s too tight, the wire will not be able to spin.

About to wrap the copper wire around the magnets (not too tight!)

Step 3: Bend top of copper wire to make contact with positive terminal of battery

We want the copper wire to make contact with the positive terminal of the battery (with the nub).

I bent the top of the copper wire with the wire cutters to make contact with the battery like this:

Bent piece of copper wire touching the positive end of the battery

Step 4: Place the wire on the battery and magnets

Hold the wire in place until the motor starts spinning, then release it gently.

Witness your homopolar motor in action!

Video of the homopolar motor in action

The technology behind the Homopolar Motor experiment

This experiment teaches:

  • Basic principles of electricity and magnetism
  • Simple machines
  • Hands-on learning

How it works

Building a homopolar motor is a great way to show the relationship between electricity and magnetism.

A copper wire is placed around the battery and comes into contact with the positive end of the battery, and a neodymium magnet is placed on the negative end of the battery.

When the exposed end of the wire touches the magnet, it completes the circuit, creating a closed loop for the electric current. This current flows through the wire, creating a magnetic field around it.

The interaction between the magnetic field and the magnet causes the wire to spin, creating a simple motor.

Basic principles of electricity and magnetism

This homopolar experiment is a way to show kids how electricity and magnetism work and how those two things can be used together to create movement!

In our experiment, we are making an electromagnetic motor. When we connect the battery to the copper wire, we are pushing an electric current through the wire, which creates a magnetic field.

That magnetic field causes a force with the magnet that we introduce, which causes the copper wire to start spinning and creates a motor.

If you think this is fascinating, check out this great explanation about electromagnetic and electric motorsOpens in a new tab..

Simple machines

This experiment is a great way to teach kids that machines and motors do not necessarily have to be complex!

By building a homopolar motor, we are building a very basic, but working electric motor like those used in electric vehicles, wind turbines, and small toy electric cars.

Hands-on learning

Since this is an experiment that your child can actively participate in, it’s a great hands-on learning experience for them! Just be sure not to hold the wire and run the motor for too long, since the wire itself can get hot after a few seconds.

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