A poster on PTSOS claims a back EMF is produced by the movement of a buzzer's armature. If so, in a vacuum, it would result in a greater back EMF, because the armature would be dragged less, which would result in the electromagnet consuming less power. I think the changing mag. field will result in an eddy current which will do the opposite, i.e. oppose the motion of the armature. What think you-all?