In a D.C. generator the critical resistance refers to the resistance of_____________?

A. double the number of poles
B. same as the number of poles
C. half the number of poles
D. two

A. Graphite brushes
B. Carbon brushes
C. Metal graphite brushes
D. None of the above

A. external current
B. armature current
C. shunt current
D. load current

A. to avoid sudden loading of the primemover
B. to avoid mechanicaljerk to the shaft
C. to avoid burning of switch contacts
D. all above

A. to reduce eddy current losses
B. to enhance flux density
C. to amplify voltage
D. to provide mechanical balance for the rotor

A. Shunt generators
B. Series generators
C. Compound generators
D. None of the above