What is role of split ring in an electric motor ?

Split rings keep the current flowing in the same direction or the motor turning in the same direction

 Split ring is nothing but commutator.It is soldered with the rectangular coil.whenever coil moves,it also moves and keeps the coils in contact with the carbon brushes so as to complete the circuit..Please note tht the carbon brushes r not made of carbon bt of Cu. 

  The split ring in the electric motor acts as a commutator. The commutator reverses the direction of current flowing through the coil after each half rotation of the coil. Due to this reversal of the current, the coil continues to rotate in the same direction.