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‣  Multiple Choice Question (MCQ) of D.C. Machines page-10‣  Multiple Choice Question (MCQ) of D.C. Machines page-9‣  Multiple Choice Question (MCQ) of D.C. Machines page-8‣  Multiple Choice Question (MCQ) of D.C. Machines page-7‣  Multiple Choice Question (MCQ) of D.C. Machines page-6‣  Multiple Choice Question (MCQ) of D.C. Machines page-5‣  Multiple Choice Question (MCQ) of D.C. Machines page-4‣  Multiple Choice Question (MCQ) of D.C. Machines page-3‣  Multiple Choice Question (MCQ) of D.C. Machines page-2‣  Multiple Choice Question (MCQ) of D.C. Machines page-1‣  MCQ of D.C motor page-4‣  MCQ of D.C motor page-3‣  MCQ of D.C motor page-2‣  MCQ of D.C motor page-1

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SymbolsTransformerRelayPower-SystemBasic-electricalACSR-ConductorCircuit-BreakerInterview-questions-of-Basic-ElectricityInterview-questions-of-transformerInsulatorCurrent-TransformerMCQMCQ-powersystemThermal-power-stationInterview-questions-of-Power-SystemPower-ElectronicsInterview-questions-of-Underground-CableInterview-questions-of-IlluminationIlluminationMCQ-of-ElectronicsMCQ-of-Basic-ElectricalMCQ-of-Transformers MCQ-of-D.C-motor MCQ-of-D.C-generatorsMCQ-Control-SystemMCQ-Measurementsmcq-of-Generation-power-systemMCQ-of-Induction-MotorMCQ-of-Transmission-Distribution

Multiple Choice Question (MCQ) of D.C. Machines page-9

81. If the back emf of a dc motor suddenly vanishes

a) The motor will run faster
b) The motor will start hunting the efficiency of the motor will increase
c) The motor will start hunting
d) The motor will burn out

Ans: (d)

82. If the supply voltage to a shunt motor is increased by 25%, which of the following will decrease?

a) Starting torque
b) Full load speed
c) Full load current
d) None of these

Ans: (b)

83. In dc motor, which of the following part can withstand the maximum rise in temperature?

a) Armature winding
b) Field winding
c) Commutator winding
d) Slip rings

Ans: (b)

84. A dc shunt motor has external resistance R1 in the field circuit and resistance R2 in the armature circuit. The starting armature current for the motor will be minimum when

a) R1 is minimum and R2 is maximum
b) R1 maximum and R2 is minimum
c) Both R1 is minimum and R2 is maximum
d) Both R1 is minimum and R2 is minimum

Ans: (a)

85. Two dc series motor are coupled. One motor runs as generator and the other as motor. The friction losses of the two machines will be equal when

a) Both operate at same voltage
b) Both have same back emf
c) Both have same speed
d) Both have same excitation

Ans: (c)

86. Two dc series motor are mechanically coupled. One machine runs as motor and the other as generator. The iron losses of the two machines will be identical when

a) Both have the same excitation
b) Both have the same speed
c) Both have the same back emf
d) Both operate at the same voltage

Ans: (a)

87. The brush voltage drops in dc in / of the order of

a) 2 V
b) 10 V
c) 20 V
d) 40 V

Ans: (a)

88. The armature torque of a dc motor is a function of its

a) Field flux alone
b) Armature current along
c) Speed alone
d) Both field flux and armature current

Ans: (d)

89. The shaft torque of a dc motor is less than its armature torque because of

a)Copper losses
b) Mechanical losses
c) Back emf
d) Rotational losses

Ans: (d)

90. Under constant load condition, the speed of a dc motor is effected by

a) Field flux alone
b) Armature current alone
c) Back emf
d) Both armature current and field flux

Ans: (a)

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