The working principle of a DC generator is to convert the alternating electromotive force induced in the armature coil into a DC electromotive force when it is led out from the brush end by the commutator in conjunction with the commutation effect of the electric brush.
The direction of induced electromotive force is determined according to the right-hand rule (the magnetic induction line points towards the palm of the hand, the thumb points towards the direction of the conductor's movement, and the other four fingers point towards the direction of induced electromotive force in the conductor).
The direction of force acting on a conductor is determined by the left-hand rule. This pair of electromagnetic forces forms a torque acting on the armature, which is called electromagnetic torque in a rotating motor. The direction of the torque is counterclockwise, attempting to make the armature rotate counterclockwise. If this electromagnetic torque can overcome the resistance torque on the armature (such as the resistance torque caused by friction and other load torques), the armature can rotate counterclockwise.
