Draw a labelled diagram of an electric motor. Explain its principle and working.
What is the function of a split ring in an electric motor?

According to the principle of an electric motor, when a rectangular current carrying conductor is placed in a magnetic field, a couple of forces act on it and try to rotate the conductor in the magnetic field.

Some devices in which electric motors are used: fans, grinders, washing machines, etc.  

An electric motor works on the principle of magnetic effect of electric current. In an electric motor, a rectangular coil ABCD is placed between two magnets in poles N and S. Now, the current flows in the direction ABCD from the commutator half-ring P and brush X, and leaves via commutator half-ring Q and brush Y continuously. When current is passed into the coil, it produces a magnetic field around it. The two magnetic fields interact and cause the coil to rotate anticlockwise and clockwise alternatively. When the coil rotates, the shaft (or, axle) attached to it also rotates. In this way, electrical energy supplied to the motor is converted into mechanical energy.

The role of the split ring (or, commutator) in an electric motor is to reverse the direction of current in the coil of the motor.