Electrical energy is converted in into mechanical energy in an electric motor.
Working of electric motor:
As shown in the diagram, when a current is passed through the coil PQRS the coil starts rotating anti clockwise because a downward force acts on length PQ and at the same time an upward force acts on RS. Therefore, the coil rotates in anti clockwise direction. In the length PQ, current flows from P to Q and magnetic field acts from left to right. According to Fleming's left hand rule a downward force acts on the length PQ and an upward force acts on length RS. These two forces causes the coil to rotate anti clockwise.
When coil complete half rotation, the position of PQ and RS interchange, the half ring D comes in contact with brush A and half-rign C comes in contact with brush B, therefore the direction of current in coil PQRS gets reversed. Now the current flows through the coil in the direction SRQP. The direction of the current through the coil PQRS reverse after every half rotation. As a result, the coil rotates in same direction. The split rings help to reverse the direction of current in the circuit.