For a dc machine shunt resistance and armature resistance values are

• A. Low and Low
• B. Low and High
• C. High and High
• D. High and Low

Answer: (D)

In DC machine the field resistance is low i.e the field resistance consist of less number of turns having the large cross-section area. While the resistance of shunt is high i.e the more number of turns and smaller cross-section area.
The resistance of the shunt field winding is large so that current in the winding is small compared to the rated armature current of the machine. To produce the necessary m m.f.. the winding consists of many turns.
The resistance of the series field winding is made as low as possible so that voltage drop across the winding is minimum. To produce the same flux at rated conditions, the turns of a series winding are fewer than those of a shunt winding since the series winding carries the rated current of the machine.