Simplest motor - screw, magnet, wire and battery.
I've recently presented some fun bits at a Google Event (#GoogleATU), and I had so many requests for more info, that I decided I'll write up my tricks for all to enjoy. if (( technology == magic ) && (magician's code)) return (void); // nah, ignore First up: Homopolar motor . It's not my idea, I have to confess. It was Farraday's idea and he first did this demo in 1821. What do you need: 1) A battery. Round ones work best. Just take a normal AA battery, one that you won't mind throwing away, as you'll pull a lot of current through it. Expert tip: For best results, find one where one of the poles on the battery is not perfectly flat. You ideally want it to be a bit rounded or with a slight tip on it to reduce the friction with the screw 2) A screw. Expert tip: This could be a nail or anything else really, but it needs to a) conduct electricity and b) magnetic field. You want one that is as heavy as your magnet can hold. Too