Homopolar Motor: Clean Energy Science Project for 5th Grade

This video that we saw on The Kid Should See This prompted me to buy the supplies to try this at home with my son:

Supply List for Homopolar Motor

I bought the wrong magnets so I would suggest you buy this smaller one instead. It’s less expensive too!

Neodymium Magnet, $10

Be careful with these magnets. Make sure no one puts them in their mouth. Swallowing neo magnets is dangerous. Also, do not put it near cell phones or computers. These are very strong magnets!

4 Yards of Copper Wire, $3.50

Wire Cutters, $4.37

You could use scissors instead.

AA Battery, $6

You just need one AA, C, or D-cell battery. The D-cell battery fits the best on the Neodymium battery that I specified but the AA battery worked fine too. I would just use whatever you have handy.

(Note that you can use the magnets, wire cutters, and copper wire for more experiments like this homopolar race car, homopolar tiny dancers, or a simple electric toy train.)

After we had our supplies, we watched a background video on how the homopolar motor works from a UCLA professor. I was hoping to understand the physics behind this science project. The professor also built the homopolar motor and it looks so easy!

Background Video from UCLA Professor on Homopolar Motor

A homopolar motor is a direct current electric motor with two magnetic poles, the conductors of which always cut unidirectional lines of magnetic flux by rotating a conductor around a fixed axis so that the conductor is at right angles to a static magnetic field. from Wikipedia

A homopolar motor creates rotational movement because of what is known as the Lorentz force. What’s happening is that electrical current is flowing from the positive terminal of the battery to the negative and into the magnet. From First 4 Magnets

Lorentz Force: the force that is exerted by a magnetic field on a moving electric charge.

So, we are still a little mystified by the physics behind the homopolar motor but the setup seems to create a magnetic field that sends forces out and then down, thus causing the wire to spin. The Lorentz Force is new to us. We have enough information to get started.

Our first obstacle is the Neodymium Magnet. I accidentally bought the much bigger one-inch size ones that are very powerful. We discover spacers between the three magnets which, of course, means the current can’t pass through all three. It’s a struggle to remove the spacers and get just one. My fingers get smashed in the process; these magnets are strong!!

Next, my son creates the wireframes that go around the setup. No matter how carefully he builds them, he can’t seem to get them spinning. On a bright note, the battery which is on top of the Neodymium magnet is getting hot. There’s definitely energy being created and conducted but the darn thing won’t spin.

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