741. Sparking, is discouraged in a D.C. motor because_____________?
A. it increases the input power con-sumption
B. commutator gets damaged
C. both A. and B.
D. none of the above

742. Speed control by Ward Leonard method gives uniform speed variation_____________?
A. in one direction
B. in both directions
C. below normal speed only
D. above normal speed only

743. Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be_____________?
A. level compounded
B. under compounded
C. cumulatively compounded
D. differentially compounded

744. Following motor is used where high starting torque and wide speed range control is required?
A. Single phase capacitor start
B. Induction motor
C. Synchronous motor
D. D.C. motor
E. None of the above

745. In a differentially compounded D.C. motor, if shunt field suddenly opens____________?
A. the motor will first stop and then run in opposite direction as series motor
B. the motor will work as series motor and run at slow speed in the same direction
C. the motor will work as series motor and run at high speed in the same direction
D. the motor will not work and come to stop

746. Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of_____________?
A. D.C. series motor
B. D.C. shunt motor
C. induction motor
D. all of above motors

747. Which of the following motor has the poorest speed regulation ?
A. Shunt motor
B. Series motor
C. Differential compound motor
D. Cumulative compound motor

748. As -the load is increased the speed of D.C. shunt motor will____________?
A. reduce slightly
B. increase slightly
C. increase proportionately
D. remains unchanged

749. The armature torque of the D.C. shunt motor is proportional to____________?
A. field flux only
B. armature current only
C. both A. and B.
D. none of the above

750. Which of the following method of speed control of D.C. machine will offer minimum efficiency ?
A. Voltage control method
B. Field control method
C. Armature control method
D. All above methods

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