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?

Explanation

Principle. Electric motor is based upon Fleming.s left hand rule. When a current carrying conductor capable of free movement is placed in a magnetic field, it experiences a mechanical force and begins to move in a direction given by Fleming.s left hand rule.
Construction. A DC motor consist of a single coil ABCD called armature between the pole pieces of a magnet as shown in fig. Armature consists of a coil of a large number of turns of insulated wire wrapped on a soft iron core. The two ends of the armature are connected to segments `S_(1)` and `S_(2)` of a commutator. The brushes `B_(1)` and `B_(2)` kee their contact with the commutator as it rotates.
Working. A direct current from a battery is passed through armature. The current flows in the coil along ABCD as shown in Fig. The limb AB of the coil experience downwards and CD of the coil experience upward force in accordance with Fleming.s left hand rule.These two equal and opposite forces constitute a couple tending to rotate the coil in clockwise direction. After half the rotation, brush `B_(1)` has contact with `S_(2)`

and brush `B_(2)` with `S_(1)`. The direction of the current gets reversed. The current now flows along DCBA instead of along ABCD. Limb DC experiences downward and BA experiences an upward force in accordance with Fleming left hand rule.
The process repeats itself and motion of armature becomes continuous after some time.
Split rings help in reversing the current in the coil after every half rotation.