|MadSci Network: Engineering|
Essentially, there is no difference between a DC motor and a DC generator. The little 1.5 volt motors have two "C" shaped magnets glued inside the case to act as the north and south poles. The rotor contains three lobes that are iron with wire wrapped around them. The lobes are connected to the shaft you see coming out of the motor case, and the attraction between the lobes and the permanent magnets makes the shaft turn. The wire connects to the battery through what is called commutator - a set of rotary contacts that insure the proper voltage is fed to each lobe as it passes each magnet. Can this be used as a generator? Yes. I did an experiment with one. I drilled a small hole in the eraser of a wooden pencil - just a little smaller than the diameter of the shaft of the motor. I put the motor in a vise, stuck the pencil eraser on the motor shaft, put the other end of the pencil in a drill, as you suggested, and at 1500 rpm was able to generate about 1/4 volt. Not 1.5 volts because, when 1.5 volts is applied to the motor it turns at very high speed, much greater than 1500 rpm, and these small mtors are very inefficient. At least this experiment verifies the answer that there is no electrical difference between a DC generator and a DC motor.
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