The working principle of DC generator is to change the AC electromotive force induced in the armature coil into DC electromotive force when it is led out from the brush end by the commutator and the reversing action of the brush.

    The direction of the induced electromotive force is determined according to the right hand rule (the magnetic induction line points to the palm of the hand, the thumb points to the direction of the conductor movement, and the other four fingers point to the direction of the induced electromotive force in the conductor).