This looks like fun! To make your own electric train, you'll need coiled copper wire, a battery, and 4 strong magnets. Attach the magnets to the end of the battery and place the "train" inside the coiled wire.
The toy train zips along the copper track, which you can arrange in a circle to keep the movement going.
I'm going to admit my ignorance: I'm not really sure why this works. Some YouTube commenters say that this toy is a homopolar motor, which is a type of electric motor in which the surrounding copper wire completes a circuit.
Commenters, is that correct?
-via Twisted Sifter