I have always been fascinated by how simple homopolar motors are. Kids are blown away by the immediate fun. But not just kids, everyone wants to check it out. Made only of a battery, a magnet, and copper wire, this simple motor can get really hot. It’s hard to play with them without forgetting and grabbing the hot wire or battery by mistake. I wondered if I could build little light weight wood structures to make them more finger safe. Getting the perfect wire shape can also be tricky, so I have to consider balance and stability, and of course see how fast I could get it to spin.
I’m really psyched about what I have cooked up in the JEMTOY studio, because these things can really spin. The design is laser cut from 1/4″ maple plywood, and is easy enough for anyone to put together. Here is a video of me assembling the JEMTOY Homopolar Motor Kit so you can see how crazy cool it is. I mean, for science, that is.
To complete a homopolar motor kit you will need to order several different items from various on line vendors. Have a few extra AA batteries on hand, which this toy will eat up in a one-hour sitting. You sorta just play with it until your battery gets hot and dies. It’s fun. To build the kit you will need some super glue or white glue to connect the wood pieces together, and a wire stripper/snipper or hobby knife to strip 1/2″ of plastic insulation off the ends of the two little wires. Be careful if you use a hobby knife, okay? Those things can be unpredictable. You might need a little screwdriver to tighten the bolt, but finger tight should work if you don’t have one. Really, this is a very easy kit to build. Check out the video, and get ’em while they’re hot at: https://www.etsy.com/shop/JEMTOY
EACH JEMTOY HOMOPOLAR MOTOR KIT REQUIRES:
- 7 Laser Cut Wood Pieces (Laser cut your own. SVG file available at my etsy)
- 1 Brass 4-40 Nut and 3/4″ long Brass Bolt (maybe buy 1 brass nut and bolt at your local hardware store instead of a pack of 100 on line)
- 1 Neodymium Rare Earth Cylinder Magnet – order from allelectronics.com
- 2 five inch lengths of Insulated Hook Up Wires RED BLACK
- White glue or super glue to hold the wood pieces together
- 2 or 3 AA BATTERIES!!! THIS TOY EATS BATTERIES AND GETS HOT HOT HOT!
OH NO! MORE SCIENCE! The nut and bolt in this kit are made of brass, not steel like most nuts and bolts. Steel is ferrous, which means it contains iron. Iron is magnetic, and a steel bolt would snap tight to the magnet, and then, the homopolar motor would not spin. The brass bolt is nonferrous, so it does not stick in place to the magnetized battery top, but is still conductive so the electricity can pass through the motor. So much to think about for such a simple device, right?
TIPS AND TRICKS FOR FASTEST SPINNING KUNG-FU ACTION
- Let battery and magnet cool before touching it.
- Flip the magnet – sometimes it spins faster the other way!
- Use a fresh AA battery – remember it gets HOTTER the longer it spins!!!
- Glue the wood pieces together – white glue or super glue will work.
- Adjust wires on bottom to touch magnet loosely – not too tight.
- Don’t forget it or leave motor spinning too long – battery gets hot and could leak, pop, or explode! (I have never seen it do this, but it seems possible, so I’m very careful)
- Parental guidance suggested for the wee ones – battery gets HOT I tell you.
Kids like that it’s slightly dangerous because kids like to be challenged. Every second you play with this homopolar motor kit, you will be learning, thinking, wondering, and expanding your understanding of the universe. For reals. It’s that cool. Great rainy day project to keep them busy for hours, or an amazing way to share the wonders of magnets and electricity with your students. Just keep them informed about how hot the battery gets, and let them have at it. Perfect project for science fairs, S.T.E.A.M. projects, maker faire booth. Kids have fun learning engineering, design, and the basics of how an electric motor works.
Google and Wikipedia have all the scientific explanations if you want to search the term homopolar motor. No matter how many times I read that stuff, I have to admit, it just looks like magic to me, so that’s another thing I love about it. I think the darn thing is magic!