This simply is the simplest motor on earth! The most expensive thing in this motor is the torch battery! The other parts are a broad rubber band from an old bicycle tube, a metal strip (broken stove pin), a cheap ferrite magnet and one meter of motor rewinding wire. The rubber band keeps the two metal strips in contact with the battery terminals. There is 1.5-volts across the metal strips. If you connect them with a torch bulb it will glow. Wind the copper wire on an old battery. There will be about 10-12 loops in the coil. Tie the ends on the coil (this prevents the loops from separating). Then straighten them so that they jut out diametrically opposite each other. If you now put the ends of the coil in the holes of stove pins no current will flow through the coil (because both the ends are coated with insulation varnish). Now scrape of all the varnish from one end (this whole end will be shining copper). On the other end, scrape the varnish only from three sides, leaving the insulation intact on one side. The little strip of insulation acts like a switch. This amazing "brush" or "commutator" switches the current on and off to the coil in every single rotation.
After putting the coil in the holes of the metal strips you will have to "kick start" it. Once it gets going, it will keep rotating until the battery drains off! Children have loads of fun making this motor. They do a lot of experiments with it, too. What happens if the length of wire is double? Or half? What happens if the wire is thicker, thinner? What happens if you change the cross-section of the coil? What if you add another battery, or bring another magnet on top? There is so much in it to discover for an inquisitive child.