Congratulations on harnessing one of the fundamental forces of the cosmos, right on your table! The universe functions because of four forces: the strong nuclear force, weak nuclear force, gravity, and of course the electromagnetic force, which is what makes your homopolar motor spin. In this instance, it’s known as the Lorentz force, and it’s created when electric charges flow inside a magnetic field. In your motor, the battery provides the charge, the wire provides the path for it to flow, and the magnet, of course, provides that all-important magnetic field.
One of the amazing and fun things about homopolar motors is that because those three basic elements are all you need to generate the Lorentz force, as long as they’re all present, you can arrange them in essentially any configuration: that’s why the “wing” and “spiral” builds both work, as well as the hearts, flowers, and other creative wire designs you’ve come up with, and the bonus build, below.
It also means you can experiment with the motor by changing the current and/or the magnetic field. Current can by increased with different battery sizes, or more effectively by stacking batteries in series. A magnetic field can also be increased by stacking magnets together; this trick works up to the point where the stack is as long as the diameter of the magnets (so the four magnets we’ve provided are already at maximum power when used together; but you could try magnets with a larger diameter).
With that in mind, here are a few more things to explore:
- Changing the direction of the motor! Just flip the magnet around so it’s other pole is attached to the bottom of the battery
- See what you can do to alter the speed of the rotation: try bending the wire, or changing the type of battery.
- Experiment with new shapes for the wire! Make it wider, or like a sculpture, see if it needs to surround the battery or not
And here are a few tips to help with your builds:
- The more symmetrical your wire, the better it stays connected to the top terminal of the battery, so it will spin more easily. You can also flip the battery over to see if the contact point sits better on the bottom than the top
- Our directions give you plenty of wire for large “wings” to make a dramatically sized motor, but any length of wire will work, as long as it’s long enough to contact the battery on one end and is inside the magnetic field on the other.
- Eventually, your motor may slow down or even stop working; this is because the motor’s operation is draining the battery; just switch it out for a fresh one.
- When operating a homopolar motor, you’re essentially short-circuiting the battery, so it can heat up; be careful.
We’ve also got a bonus build that you can make with the elements we’ve included in your kit, plus two safety pins, and some tape.
Directions:
- Attach the magnets to the head of the nail or screw
- Attach point of the nail/screw to the battery – with the magnets there, it should just stick. We find the best results when attached to the “bump” terminal of the battery
- Take a length of your wire, and hole it so one end is in contact with the top of the battery, and the other is touching – or inside the magnetic field of – the magnets.
- The nail/magnet construction will rapidly spin! You can put a piece of tape on the magnets and watch it whirl around to make the effect more pronounced.
And finally, railguns! These futuristic weapons often show up in sci-fi franchises: you may have seen them in the Transformers movies, video games like Halo and Mass Effect, or The Expanse. A railgun is constructed so that an electrical current and magnetic field produce a perpendicular force that shoots the projectile out at a tremendous speed – the exact same Lorentz force that spins the wire of your homopolar motor! And that force makes the projectiles go fast. How fast? Current (ha!) railguns can fire a projectile at Mach 6 (7,400 kmh/5,400 mph). That would take you from LA to New York in less than an hour, or New York to Paris in about 67 minutes.
It won’t fly you across the ocean, but we hope you find this homopolar motor kit provides hours of curiosity-satisfying experimentation!