It is a device that converts electrical energy into mechanical energy.
When the current-carrying coil is placed in a magnetic field. It experiences a force and rotates.
Its construction is similar to that of d.c. the generator works in the backward direction.
The coil wound on a soft iron cylinder(core). The (coil+core) is called the armature. Two halves of a ring A, A (split rings) are called the commutator. B, B are the carbon brushes that slide over split rings and connect the coil to the external circuit. The magnetic field is provided to the coil of the motor by the electromagnet. The battery provides current to the coil of the motor provides current to the coil of the motor.
When the carbon bushes B, and B are connected to the battery. Current flows through the coil and it becomes a bar magnet. The north pole of the coil is repelled by the north pole of the permanent magnet and the coil is made to rotate in a clockwise direction by the mutual repulsion due to the resultant magnetic field of the electromagnet and that of the coil.
After rotating the coil through an angle of 180, the north pole of the coil will be in front of the south pole of the permanent magnet and will be retarded from rotating away from that position. However, when it reaches to that position, the sliding contact on the split ring slides over the gap of the ring and the current flowing through the coil reverses. This inturns reverses the poles of the coil and so once again the repulsion is maintained and as a result rotation on continues.