make this homopolar motor with a battery some wire and a strong magnet

With this post you’ll learn how to make a motor. We’ve mentioned Michael Faraday while talking about Christmas before because of his involvement with the Christmas lectures. It seems right, then, that we make ourselves a Christmas toy with Faraday’s invention – the homopolar motor! It might be a bit different now but when I was a kid the most useful thing you got for Christmas was a pack of batteries. Everything needed 15 batteries * to even start working. Then a day later* you needed 15 and a half more.

*some numbers may be exaggerated

Batteries not included

Now, a lot of things are supplied with battery packs built in. You won’t find many phones or laptops that you can take the batteries out of any more. This is thanks to massive progress in the technology that goes into making the battery packs more efficient. We’ve also got better rechargable batteries which are more sustainable and cheaper to use in the long run!

So what should we do with all the batteries that are left?

The Homopolar Motor

We can use them to make a whole new toy just using some wire and a magnet. It will spin and spin until the battery runs out or it gets a bit too hot for comfort…

What will you need?

  • A battery
  • A piece of copper wire
  • A strong, small magnet – preferably a Neodynium magnet

A safety notice – really strong magnets like Neodynium magnets work for this because of how strong they are. But please do be careful with them. They are typically really small – so it is possible to swallow them! Swallowing one isn’t so much of a problem… but if you swallow anything else magnetic afterwards then the two things will find each other inside your body and nothing will get in their way – not your stomach lining, not your intestines, not your health. These magnets are really dangerous to very young children so please do be careful.

How to make the motor

Place the magnet onto one end of the battery. The flat end of the battery will be easier so that everything balances.

Bend the wire so that there is a curve in the wire that will balance on the top of the battery and a long piece stretching down that will contact the magnet at the bottom of the battery. If you have wire touching the magnet and the top of the battery at the same time then the wire will start to turn. It will spin around and around once you’ve got it balanced just right!

If at first you don’t succeed..

You will probably need to tweak your wire shape a lot to get this balanced perfectly. you can try and make a sculpture if you’re really patient. I attempted to make a dinosaur because my wife was playing Jurassic Park at the time I was doing this… judge for yourselves whether I’ll make an artist one day…

Sometimes you might just need to give it a little push…

More Examples

You can make this motor into a tiny car or use it to make a spinning object levitate and spin. You can even make something that looks a lot more like a useful motor with an axle!

So what’s going on?

There are a lot of different things going on here so brace yourselves – it’s complicated stuff time.

Magnetic Fields

First of all, we have a magnet. The magnetic field goes from one side of the magnet – the north pole – around in a big circle to the other side of the magnet – the south pole. You can imagine lines showing this magnetic field going up away from the magnet in the same direction as the battery.

The forces involved in the homopolar motor you've made

Electric Fields

At the same time we have some electricity flowing around a circuit – we call this a current. Current is all about the flow of electrons so they need somewhere to start off (the battery) and somewhere to go (around the wire) and they need to end up back at the start line! Current will flow once you have the wire contacting the top of the battery and the bottom of the magnet at the same time. As this current flows it makes another type of field – an electric field. Electric fields are fancy and go roughly in the direction that the current is flowing which means they go across the face of the magnet.

A Fight in the Fields

We have two fields then – an electric and a magnetic field – and they are going in opposite directions to each other. One is going up and down, and one is going left and right (as I’ve drawn it in the picture).

There is one direction left in this drawing. The direction towards us and away from us. What happens when an electric field and a magnetic field is that the two fields fight it out and try to repel each other like trying to push two of the same poles of a magnet together. The only direction that is left between the two fields for anything to be repelled is towards us or away from us! The wire gets repelled and pushed in this direction – which ends up with motion around the battery so the whole thing spins!

If you want to reverse the direction the wire spins, you need to flip over the direction of one of the fields. Flip the battery upside down so that the current is flowing the opposite way and it should swap the direction the wire spins.

So is this useful for anything?

Not really, no. Not anymore, at least. It was invented almost 200 years ago by Michael Faraday and was really the first electric motor ever made. It’s called the homopolar motor and without this one being invented we probably wouldn’t have ended up with a huge chunk of the electric-based technology we have now! They are simple to build and luckily we can understand them now – build one yourself!

Try it out at home and share your creation with me on twitter using #XPeriMas!

You can buy neodynium magnets easily online – they aren’t too expensive either. Just remember to be careful with them.


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