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MCQs

Dc Motors

Total Questions : 240 | Page 7 of 24 pages
Question 61. Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator?
  1.    Providing laminations in armature core
  2.    Providing laminations in stator
  3.    Using nonmagnetic material for frame
  4.    Using material of low hysteresis coefficient for armature core material
 Discuss Question
Answer: Option D. -> Using material of low hysteresis coefficient for armature core material
Question 62. Which of the following loss in a D.C. generator is dissipated in the form of heat?
  1.    Mechanical loss
  2.    Core loss
  3.    Copper loss
  4.    All of the above
 Discuss Question
Answer: Option D. -> All of the above
Question 63. The hysteresis loss in a D.C. machine least depends on
  1.    Frequency of magnetic reversals
  2.    Maximum value of flux density
  3.    Volume and grade of iron
  4.    Rate of flow of ventilating air
 Discuss Question
Answer: Option D. -> Rate of flow of ventilating air
Question 64. Hopkinson's test on D.C. machines is conducted at
  1.    No load
  2.    Part load
  3.    Full load
  4.    Overload
 Discuss Question
Answer: Option C. -> Full load
Question 65. Regenerative method of braking is based on that
  1.    Back e.m.f. is less than the applied voltage
  2.    Back e.m.f. is equal to the applied voltage
  3.    Back e.m.f. of rotor is more than the applied voltage
  4.    None of the above
 Discuss Question
Answer: Option C. -> Back e.m.f. of rotor is more than the applied voltage
Question 66. In the D.C. motor the iron losses occur in
  1.    The field
  2.    The armature
  3.    The brushes
  4.    The commutator
 Discuss Question
Answer: Option B. -> The armature
Question 67. In D.C. machines fractional pitch winding is used
  1.    To improve cooling
  2.    To reduce copper losses
  3.    To increase the generated e.m.f.
  4.    To reduce the sparking
 Discuss Question
Answer: Option D. -> To reduce the sparking
Question 68. In which of the following applications D.C. series motor is invariably tried?
  1.    Starter for a car
  2.    Drive for a water pump
  3.    Fan motor
  4.    Motor operation in A.C. or D.C.
 Discuss Question
Answer: Option A. -> Starter for a car
Question 69. Which D.C. motor has got maximum self loading property?
  1.    Series motor
  2.    Shunt motor
  3.    Cumulatively compounded motor
  4.    Differentially compounded motor
 Discuss Question
Answer: Option D. -> Differentially compounded motor
Question 70. For constant torque drive which speed control method is preferred?
  1.    Field control
  2.    Armature voltage control
  3.    Shunt armature control
  4.    Mechanical loading system
 Discuss Question
Answer: Option B. -> Armature voltage control

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