Now here's a question (specially for the electrical engineers amongst you...!): why exactly does the armature rotate? To help you figure it out, here's how the motor is set up. The armature is made of magnet wire with a non-conducting enamel coating. The axle supports (in which the armature axle rests) are made from a thicker wire which normally has a plastic insulation; we stripped the plastic insulation exposing the bare wire. Each axle support is connected to one end of the battery, and there's a magnet under the armature. In addition, there's a clever little trick (described in the instructions). Can you figure it out?
Talking about the Science Fair, this year Leigh Klotz and I are running the Science Fair at our kids' school. We put together a page of links to web resources for Science Fair projects. Check it out---you'll find all kinds of really great projects.