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1) Which D.C. motor has got maximum self loading property? a. Series motor b. Shunt motor c. Cumulatively compounded ‘motor d. Differentially compounded motor
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2) Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads? a. Series motor b. Shunt motor c. Cumulatively compounded motor d. Differentially compounded motor
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3) If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens__________? a. nothing will happen to the motor b. this will make armature to take heavy current, possibly burning it c. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses d. motor will run at very slow speed
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4) D.C. series motors are used______________? a. where load is constant b. where load changes frequently c. where constant operating speed is needed d. in none of the above situations
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5) For the same H.P. rating and full load speed, following motor has poor starting torque_____________? a. shunt b. series c. differentially compounded d. cumulativelyc’ompounded
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6) In case of conductively compensated D.C. series motors, the compensating winding is provided______________? a. as separately wound unit b. in parallel with armature winding c. in series with armature winding d. in parallel with field winding
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7) Sparking at the commutator of a D.C. motor may result in____________? a. damage to commutator segments b. damage to commutator insulation c. increased power consumption d. all of the above
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8) Which of the following motor is preferred for operation in highly explosive atmosphere ? a. Series motor b. Shunt motor c. Air motor d. Battery operated motor
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9) If the supply voltage for a D.C. motor is increased, which of the following will decrease ? a. Starting torque b. Operating speed c. Full-load current d. All of the above
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10) Which one of the following is not the function of pole shoes in a D.C. machine ? a. To reduce eddy current loss b. To support the field coils c. To spread out flux for better uniformity d. To reduce the reluctance of the magnetic path
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11) The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is______________? a. 4.0 b. 2.0 c. 1.0 d. 0.5
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12) The condition for maximum power in case of D.C. motor is______________? a. back e.m.f. = 2 x supply voltage b. back e.m.f. = | x supply voltage c. supply voltage = | x back e.m.f d. supply voltage = back e.m.f
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13) For which of the following applications a D.C. motor is preferred over an A.C. motor ? a. Low speed operation b. High speed operation c. Variable speed operation d. Fixed speed operation
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14) In D.C. machines the residual magnetism is of the order of_________________? a. 2 to 3 per cent b. 10 to 15 per cent c. 20 to 25 per cent d. 50 to 75 per cent
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15) Which D.C. motor is generally preferred for cranes and hoists ? a. Series motor b. Shunt motor c. Cumulatively compounded motor d. Differentially compounded motor
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16) Three point starter can be used for______________? a. series motor only b. shunt motor only c. compound motor only d. both shunt and compound motor
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17) 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
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18) 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
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19) 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
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20) 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
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