A DC motor is fixed with a ring-shaped permanent magnet inside, and the current flows through the coil on the rotor to generate an ampere force. When the coil on the rotor is parallel to the magnetic field, the direction of the magnetic field received by further rotation will change. Therefore, at this time, the electric brush at the end of the rotor and the conversion piece alternately contact, so the direction of the current on the coil also changes, and the direction of the generated Lorentz force remains unchanged, so the motor can maintain one direction of rotation.

The structure of a DC motor shall consist of two major parts, the stator and the rotor. The stationary part of a DC motor during operation is called the stator. The main function of the stator is to generate a magnetic field, consisting of the base, main magnetic pole, commutator pole, end cap, bearings, and brush devices. The rotating part during operation is called the rotor, whose main function is to generate electromagnetic torque and induced electromotive force, and is the hub for energy conversion of DC motors. Therefore, it is commonly referred to as the armature, consisting of a shaft, armature core, armature winding, commutator, and fan.