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MCQs

Dc Motors

Total Questions : 240 | Page 4 of 24 pages
Question 31. The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator?
  1.    Hysteresis loss
  2.    Field copper loss
  3.    Armature copper loss
  4.    Eddy current loss
 Discuss Question
Answer: Option C. -> Armature copper loss
Question 32. Which of the following load normally needs starting torque more than the rated torque?
  1.    Blowers
  2.    Conveyors
  3.    Air compressors
  4.    Centrifugal pumps
 Discuss Question
Answer: Option B. -> Conveyors
Question 33. D.C. shunt motors are used for driving
  1.    Trains
  2.    Cranes
  3.    Hoists
  4.    Machine tools
 Discuss Question
Answer: Option D. -> Machine tools
Question 34. The condition for maximum power in case of D.C. motor is
  1.    Back e.m.f. = 2 × supply voltage
  2.    Back e.m.f. =1/2 × supply voltage
  3.    Supply voltage =1/2 × back e.m.f.
  4.    Supply voltage = back e.m.f.
 Discuss Question
Answer: Option B. -> Back e.m.f. =1/2 × supply voltage
Question 35. Which of the following law/rule can he used to determine the direction of rotation of D.C. motor?
  1.    Lenz
  2.    Faraday
  3.    Coulomb’s law
  4.    Fleming
 Discuss Question
Answer: Option D. -> Fleming
Question 36. The speed of a D.C. motor can be varied by varying
  1.    Field current
  2.    Applied voltage
  3.    Resistance in series with armature
  4.    Any of the above
 Discuss Question
Answer: Option D. -> Any of the above
Question 37. Following motor is used where high starting torque and wide speed range control is required.
  1.    Single phase capacitor start
  2.    Induction motor
  3.    Synchronous motor
  4.    D.C. motor
 Discuss Question
Answer: Option D. -> D.C. motor
Question 38. The current drawn by the armature of D.C. motor is directly proportional to
  1.    The torque required
  2.    The speed of the motor
  3.    The voltage across the terminals
  4.    None of the above
 Discuss Question
Answer: Option A. -> The torque required
Question 39. The speed of a D.C. shunt motor more than its full-load speed can be obtained by
  1.    Decreasing the field current
  2.    Increasing the field current
  3.    Decreasing the armature current
  4.    Increasing the armature current
 Discuss Question
Answer: Option A. -> Decreasing the field current
Question 40. Which D.C. motor will be preferred for machine tools?
  1.    Series motor
  2.    Shunt motor
  3.    Cumulative compound motor
  4.    Differential compound motor
 Discuss Question
Answer: Option B. -> Shunt motor

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