About 13 years ago I learned of some military research into a satellite- and missile-defense device that would propel projectiles using Lenz’s law, which governs the direction of electrical current induced by a changing magnetic field. I decided to make a little gadget based on the same principle for my kids, to get them interested in science and electronics. The gadget worked — both at levitating and shooting rings, and at interesting my kids (some of them, anyway).

This design is actually the third one I tried. I had no real information on what the military was up to, so I tested my own ideas. One iteration used wire wound around a steel pipe with a short piece of aluminum rod inside. (That one didn’t work — trust me!)

Not only is this project physically exciting and intellectually stimulating, it’s also quick, easy, and inexpensive to build. Except for the 200 feet of #18 magnet wire, you can purchase everything you need at a hardware store or scavenge it from common junk.