In what device is a split-ring commutator used, and what function does it serve?
- Aa.c. generator; to change the direction of the current in the coil as it turns
- Ba.c. generator; to change the output current from d.c. into a.c.
- Cd.c. motor; to change the direction of the current in the coil as it turns
- Dd.c. motor; to change the input current from a.c. into d.c.