Principle of motor

Electrical machines run under induction principle. That is, when current carrying conductors are placed inside the magnetic field these conductor experiences some forces which is perpendicular to the conductors as well as field. Due to this force the motors starts rotating. This speed mainly depends on the following factor. The current flowing through the armature, the number of windings in the armature, field strength, and the external load connected to this armature. In an electrical motor this magnetic field is created by either placing permanent magnets or by providing external supply to this field coils.
The armature which carries conductor placed inside the field coils and the commutator and brush assembly is placed at the end of the rotor. External supply is given to the rotor windings via commutator and brush assembly. Once current flows through this conductors it experiences some force which is perpendicular to the field. Due to this force it start rotating. Commutator and brush assembly differs depends upon the type of motor.