[amp_mcq option1=”lags behind the voltage by about 75°” option2=”leads the voltage by about 75°” option3=”lags behind the voltage by about 15°” option4=”leads the voltage by about 15°” correct=”option3″]
Transformers
2. The efficiency of two identical transformers under load conditions can be determined by
[amp_mcq option1=”short-circuit test” option2=”back-to-back test” option3=”open circuit test” option4=”any of the above” correct=”option2″]
3. Greater the secondary leakage flux
[amp_mcq option1=”less will be the secondary induced e.m.f.” option2=”less will be the primary induced e.m.f.” option3=”less will be the primary terminal voltage” option4=”none of the above” correct=”option1″]
4. A transformer oil must be free from
[amp_mcq option1=”sludge” option2=”odour” option3=”gases” option4=”moisture” correct=”option4″]
5. The highest voltage for transmitting electrical power in India is
[amp_mcq option1=”33 kV” option2=”66 kV” option3=”132 kV” option4=”400 kV E. 765 kV” correct=”option1″]
Detailed SolutionThe highest voltage for transmitting electrical power in India is
6. In an actual transformer the iron loss remains practically constant from noload to fullload because
[amp_mcq option1=”value of transformation ratio remains constant” option2=”permeability of transformer core remains constant” option3=”core flux remains practically constant” option4=”primary voltage remains constant” correct=”option3″]
7. The efficiencies of transformers compared with that of electric motors of the same power are
[amp_mcq option1=”about the same” option2=”much smaller” option3=”much higher” option4=”somewhat smaller” correct=”option1″]
8. The hum in a transformer is mainly attributed to
[amp_mcq option1=”load changes” option2=”oil in the transformer” option3=”magnetostriction” option4=”mechanical vibrations” correct=”option3″]
Detailed SolutionThe hum in a transformer is mainly attributed to
9. The thickness of laminations used in a transformer is usually
[amp_mcq option1=”0.4 mm to 0.5 mm” option2=”4 mm to 5 mm” option3=”14 mm to 15 mm” option4=”25 mm to 40 mm” correct=”option1″]
Detailed SolutionThe thickness of laminations used in a transformer is usually
10. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V
[amp_mcq option1=”Its secondary current is 5 A” option2=”Its secondary voltage is 400 V” option3=”supply is incorrect? A. Its secondary current is 5 A B. Its secondary voltage is 400 V C. Its rating is 2 kVA” option4=”Its secondary current is 20 A” correct=”option4″]