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MCQs

Total Questions : 631 | Page 1 of 64 pages
Question 1. The efficiencies of transformers compared with that of electric motors of the same power are
  1.    about the same
  2.    much smaller
  3.    much higher
  4.    somewhat smaller
 Discuss Question
Answer: Option C. -> much higher
Question 2. The noise resulting from vibrations of laminations set by magnetic forces, is termed as
  1.    Magnetostriction
  2.    Boo
  3.    Hum
  4.    Zoom
 Discuss Question
Answer: Option C. -> Hum
Question 3. The power transformer is a constant
  1.    voltage device
  2.    current device
  3.    power device
  4.    main flux device
 Discuss Question
Answer: Option D. -> main flux device
Question 4. Sumpner's test is conducted on transformers to determine
  1.    temperature
  2.    stray losses
  3.    all-day efficiency
  4.    none of the above
 Discuss Question
Answer: Option A. -> temperature
Question 5. For the parallel operation of single phase transformers it is necessary that they should have
  1.    same efficiency
  2.    same polarity
  3.    same kVA rating
  4.    same number of turns on the secondary side.
 Discuss Question
Answer: Option B. -> same polarity
Question 6. In a transformer routine efficiency depends upon
  1.    supply frequency
  2.    load current
  3.    power factor of load
  4.    both (B) and (C)
 Discuss Question
Answer: Option D. -> both (B) and (C)
Question 7. No-load on a transformer is carried out to determine
  1.    copper loss
  2.    magnetising current
  3.    magnetising current and loss
  4.    efficiency of the transformer
 Discuss Question
Answer: Option C. -> magnetising current and loss
Question 8. The dielectric strength of transformer oil is expected to be
  1.    lkV
  2.    33 kV
  3.    100 kV
  4.    330 kV
 Discuss Question
Answer: Option B. -> 33 kV
Question 9. A transformer oil must be free from
  1.    sludge
  2.    odour
  3.    gases
  4.    moisture
 Discuss Question
Answer: Option D. -> moisture
Question 10. Losses which occur in rotating electric machines and do not occur in trans formers are
  1.    friction and windage losses
  2.    magnetic losses
  3.    hysteresis and eddy current losses
  4.    copper losses
 Discuss Question
Answer: Option A. -> friction and windage losses

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