In the laboratory model of a d.c. motor, a split-ring arrangement is connected to the ends of the coil.
a. (a) What is meant by a split-ring commutator? Draw a simple diagram to illustrate your answer.
b. (b) Explain clearly how the split-ring commutator helps the coil to continue rotating in the same direction although the forces on its sides change direction every half-turn.
c. (c) Describe what would happen to the motion of the coil if the split-ring were replaced by two continuous slip rings while keeping every other part of the set-up the same. Give reasons.
d. (d) State two practical advantages gained by using a soft iron core inside the coil of a motor.