I'm thinking of making an electricity generator which is rotated by hand, or possibly something like wind, or gerbils on a treadmill etc etc.. Anyway, the current and emf produced would vary depending on the velocity at which the generator is turned, correct? I therefore need a way of keeping the angular velocity constant. My idea was to somehow set a maximum velocity for the rotation of the generator, but not affect the velocity of the turning handle. I could rotate the handle at a velocity higher than the required velocity, and any extra energy could be dissipated as heat or something. Does anyone have any ideas on how to accomplish this? Or any other method which would keep the emf+current at a set value.