POWERS OF INDUCTION
This simple AC-powered coil device
uses magnetism to levitate aluminum
rings and shoot them into the air —
and aluminum isn’t even magnetic!
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
Photograph by Sam Murphy
Set up: p. 103
Make it: p. 104 Use it: p. 107
Tom Fox (
magiclandelectronics.com) is the author of numerous articles about electronics, and of three
books, most recently Snowball Launchers, Giant-Pumpkin Growers, and Other Cool Contraptions. He is
also the workshop editor at Boys’ Quest and Fun for Kidz magazines. Tom and his family own and operate
Magicland Farms (
magiclandfarms.com), a farm and roadside market in Michigan.