Motor (English: Electric machinery, commonly known as "motor") refers to an electromagnetic device that realizes electric energy conversion or transmission according to the law of electromagnetic induction.
The motor is represented by the letter M (old mark D) in the circuit, and its main function is to generate driving torque.
As the power source of electrical appliances or various machines, the generator is represented by the letter G in the circuit, and its main function is to convert mechanical energy into electrical energy.
The working principle of DC generator is to use the commutation function of brush to change the AC electromotive force induced in armature coil into DC electromotive force when it is led out from the end of brush through commutator.
The direction of induced electromotive force is determined according to the right-hand rule (the magnetic induction line points to the palm, the thumb points to the direction of conductor movement, and the other four fingers point to the direction of induced electromotive force in the conductor).