As part of a series of activities focused on Electromagnetism in our Tinkering Afterschool program with the Boys & Girls Clubs of SF and our XTech program, I decided to revisit the idea of building Homopolar Motors. These are super simplified motors that can be made sculptural by crafting a single piece of copper wire that must balance on top of a AA battery while lightly brushing by a strong magnet at the other end of the battery. I've tried it once before with young children at the Boys & Girls Clubs years ago and found that the level of precision in wire bending necessary to get a "successful" homopolar motor spinning around the battery, was especially frustrating for kids. I decided to revisit and see what I could do to design some extra supports into the activity design, while also introducing it to older, middle school aged youth.
Wire-bending Jigs Mario made these beautiful, flat jigs to create a base shape with a v shape to balance on the battery and the right spacing to reach the bottom of the battery. But he said that visitors had a hard time getting the v shape and were shoving pencils in to help make the v. So, I added these nails so that the wire could be wound around them and that works much better!
We also found that it was helpful to have some help making a ring that fits around the magnet at the bottom. These 16mm dowels work perfectly:
Flip the Battery!!
Another adjustment I made is I put the cup washer on the negative end of the battery instead of the positive. When it was on the positive end, I kept finding that the wires would get caught in the little tiny chasm between the positive bump on the battery and the washer. Using the negative side gives you a nice flat surface for the wire to spin around on:
Make a Magnet Separator!
Our HS age XTech facilitators had a really hard time separating the rare earth magnets- especially when it was just two, so he quickly made us this handy magnet separator. It could use some sanding but it works perfectly. You put one magnet in the little hole and the other sits on top. When you pass the top wood piece over them, it slides the top magnet off the one in the hole:
What’s Going On?
I did this activity as the beginning of a curriculum focused on electromagnetism and motors. I find that homopolar motors had kind of a “magic” effect on people and it can be difficult to relate them to the realities of everyday motors. So, I created a “motor in a bottle” to demonstrate what happens inside one of our super-recognizable hobby motors. Its a hobby motor without the outer casing. I had to glue the two magnets to nails in order to keep them in place and the bottle is to make sure no hair or other things get caught in the spinning coils. It’s not pretty but it works and the kids loved playing with it.
Student Work and Thoughts on Learning
The kids explored some great stuff. Some built the most minimal designs possible, some built flat designs that had a really cool way of spinning erratically when they got a lot of momentum:
Some build representationally- lots of frogs and bunnies, hearts and a butterfly:
A lot of them tried spirals which proved to be some of the fussiest. Adding feathers was interesting because it sometimes meant that the extra weight and wind resistance kept them from moving. Some of the most fun to look at were ones that played with asymetry and created interesting visual effects where the wire closest to the center appeared to stand still:
Some of the bases we made got decorated:
This girl worked really hard at trying a hinged design. If she had more time, she would had added a bit of solder at the hinges.
A Special Kind of Frustration?
I think I’ve seen kids go through a kind of frustration with this activity that is different from others. I think it partially stems from the feeling that while working on these, your piece simply either “works” or “doesn’t work.” This becomes compounded when kids see others around them with spinning motors while they are still struggling with theirs. It’s not everyone’s experience. Some were really excited to finally have something work for them and went on to try different designs. But I’ve noticed that kids who already tend towards perfectionism or have existing insecurities about their own intelligence (like those who are framed as behind in school), have an even harder time with this kind of frustration. A few of them even told me that even when they got theirs to work, it wasn't worth the effort it took for them to get there. It’s worth thinking more about...