Concept:The device uses a d.c. supply and a split-ring commutator, which are the identifying features of a d.c. motor.
Explanation:A d.c. motor has field magnets, a rotating coil, carbon brushes, and a split-ring commutator.
The split-ring commutator reverses the direction of current in the coil after every half-turn.
This reversal keeps the torque acting in the same direction, so the coil continues rotating in one direction.
Thus, the device converts electrical energy into mechanical energy.
Since the diagram shows a battery or d.c. source connected to the commutator, it cannot be an a.c. generator or an a.c. motor.
It is therefore a direct current motor.
Answer:D. d.c. motor
