Steve Maxwell, an engineer at KJ magnets, created a tiny self-propelled “car” from three neodymium magnets, one AA battery, and aluminum foil. “It is a very cool scientific experiment,” he says. “You can see the interaction between electric fields and magnetic fields.”
To build Maxwell’s tiny car, place a ring-shaped magnet on a battery’s positive post and add circular magnets to both ends. Then lay down aluminum foil as a makeshift road, smoothing out any bumps. The contact between battery and foil allows an electric current to flow. Because that electricity runs per- pendicularly to the field created by the magnets, it generates torque. This rotational force rolls the car across the foil on its magnet “wheels”-quickly draining the battery in the process.
This article was originally published in the July/August 2016 issue of Popular Science, under the title “Magnet Car.”