A brushed DC electric motor generating torque from DC power supply by using an internal mechanical commutation. Stationary permanent magnets form the stator field.
Torque is produced by the principle that any current-carrying conductor placed within an external magnetic field experiences a force, known as Lorentz force.
In a motor, the magnitude of this Lorentz force (a vector represented by the green arrow), and thus the output torque,is a function for rotor angle, leading to a phenomenon known as torque ripple.
Since this is a two-pole motor, the commutator consists of a split ring, so that the current reverses each half turn ( 180 degrees).