It's not quite a motor because the rotating magnet will just move as far as it has to in order to get the opposite poles together. You might be able to cause the movable bar magnet to make turn after turn. You could do this by turning the fixed magnet quickly end for end. This wouldn't be very practical as a motor. We Can Improve It If we could change the pole on one end of the rotating magnet just as soon as it reaches the attracting pole, it could make a complete circle. In doing that, the pole at the near end of the rotating magnet would be repelled by the stationary magnet and pushed away. As soon as the opposite end of the rotating magnet would come into the magnetic field, it would be drawn to the stationary magnet. In order to keep the "motor" running, we would have to constantly change the poles at each end on every half revolution. We Need An Electromagnet We can't reverse the poles on simple bar magnets, but we can on _electromagnets_. We can make one by wrapping a wire several times around an iron core to form a coil. This magnet will also have a N and a S pole when connected to electrical current. The big difference is that the poles can be changed instantly by reversing the current in the wire. Switching Poles Automatically The rotating electromagnet will have to be connected to the 2 wires through which we pass the current. Since it's rotating on a center shaft, we can't have a solid connection. Instead we have to extend the wires from the coil out along the shaft and let the electric contact be made with brushes which touch the wires along the shaft. [Illustration: Figure 4. A rotating electromagnet changes poles as contacts are made first one way, then the other.] This is a simple way to reverse the current in the coil of the electromagnet. Increasing Efficiency Instead of using only one pole of a stationary magnet, we can use both. This is done by shaping the stationary magnet around the path of the rotating electromagnet. This way we have the benefit of the attracting and repelling forces from both poles. The effect is doubled. We can also wrap wires around this circular iron and make an electromagnet of it. But when we wire this magnet we use no brushes because we want the current to flow in one direction only. The stationary electromagnet is called the _field_. The rotating electromagnet is the _armature_. WHAT TO DO: Make A Motor _Tools Needed:_ Pocket knife, hammer, vise (or 2 pairs of pliers). _Materials Needed_: 1 roll of No. 24 enameled wire 1 roll of electrician's tape 3 - 4" (20-penny) nails 4 - 2-1/2" (8-penny) nails 4 - 3" brads (10 penny) Wood board for motor base 2 staples or 4 small brads 2 tacks 2 - 3 volt dry cell batteries (or a 6 volt transformer). Step No. 1-Armature Wrap about 1-1/2" of a 4" nail with two layers of tape. This will be the shaft.