State the function of split ring in d.c. motor.

Hint: A d.c. motor converts electrical energy into mechanical energy. The split rings as the name suggest are two half rings that would facilitate proper rotation in one direction of the armature coil to produce mechanical energy.

Complete step by step answer:
The working of the d.c. motor is based on the principle that when a current carrying coil is placed in a strong magnetic field it experiences a torque.

The split rings connect the armature coil to the external circuit and the d.c. source. Their main function is to change the direction of current in the armature coil so that it would keep rotating in a direction. By reversing the direction periodically after each half turn it ensures that a proper torque is maintained, and the coil rotates properly. In the absence of these split rings the rotator would start rotating in the opposite direction after every half rotation. So, basically a split ring is a mechanical rectifier that rectifies alternating rotation into uniform rotation.
The correct answer is that split rings reverse the direction of current in the coils after every half turn.

Note:
Remember that Fleming’s left-hand rule for motors is used for finding the direction of current in a d.c. motor and Fleming’s right-hand rule is used for direction of induced current in d.c. generator where the thumb denotes the direction of force, index finger gives the direction of magnetic field and middle finger gives the direction of current.