Transformer MCQ Questions and Answers

241. The function of oil in a transformer is to provide

  1. Insulation and cooling
  2. Protection against lighting
  3. Protection against short circuit
  4. Lubrication
Answer
Answer. a

242. To conduct sumpners test on a transformer

  1. Only one transformer is sufficient
  2. Two identical transformers are needed
  3. Two  unidentical transformers are needed
  4. At least three transformers are necessary
Answer
Answer. b

243. The voltage regulation of a transformer at full load, 0.9 p.f. lagging is 5%. For a full load at 0.9 p.f. leading, it will

  1. Remain the same
  2. Become negative
  3. Reduce and may even become negative
  4. Increases
Answer
Answer. c

244. Power transformers are designed with

  1. Low leakage reactances
  2. High leakage reactances
  3. High all day efficiency
  4. Low  full load voltage regulation
Answer
Answer. b

245. The frequency of ac supply is increased keeping impressed voltage of a transformer constant. Its core loss will

  1. Increase
  2. Decrease
  3. Not change
  4. Depends upon the design of the transformer
Answer
Answer. b

246. The open-circuit test at rated voltage is performed on a transformer to determine its

  1. Regulation
  2. Efficiency
  3. Iron losses
  4. Copper losses
Answer
Answer. c

247. Which of the following prevents the damage to a transformer due to lightning?

  1. Buchholz relay
  2. Conservator
  3. Breather
  4. Horn gap
Answer
Answer. d

248. Step-up transformer increase

  1. Power
  2. Power factor
  3. Frequency
  4. Voltage
Answer
Answer. d

249. No-load loss of a transformer has two components. They are eddy current and hysteresis loss. In which part of a transformer hysteresis will occur?

  1. Core
  2. Breather
  3. Transformer oil
  4. Conservator
Answer
Answer. a

250. On which of the following do the eddy current losses depend?

  1. nature of the material
  2. maximum flux density
  3. frequency
  1. I, II and III
  2. II and III
  3. I and II
  4. I and III
Answer
Answer. a

251. Which of the following statement(s) is/are true?

  1. DC supply can not be used for transformers
  2. The transformer works on the principle of mutual induction.
  1. Only I
  2. Both I and II
  3. Only II
  4. Neither I nor II
Answer
Answer. b

252. The no-load current of a transformer is 20 A at a power factor of 0.20 lagging, when connected to 400 V, 50 Hz supply. Calculate the magnetizing component of no-load current.

  1. 13.4 A
  2. 16.8 A
  3. 19.6 A
  4. 18.2 A
Answer
Answer. a

253. An ideal transformer has

  1. Very high losses
  2. Very low losses
  3. Moderate losses
  4. No losses
Answer
Answer. d

254. Which of the following is not a type of construction used for single-phase transformer?

  1. Core type
  2. Shell type
  3. Berry type
  4. Roof type
Answer
Answer. d

255. Copper losses of a transformer are

  1. Directly proportional to turn ratio
  2. Inversely proportional to turn ratio
  3. Inversely proportional to square root of turn ratio
  4. Directly proportional to square of turn ratio
Answer
Answer. d

256. Which of the following statement is true about the windings of a transformer?

  1. Windings are conductively linked
  2. Windings are inductively linked
  3. Windings are not linked at all
  4. Windings are electrically linked
Answer
Answer. b

257. Basically, a booster is a

  1. Synchronous motor
  2. Capacitor
  3. Inductor
  4. Transformer
Answer
Answer. d

258. Which of the following losses in the transformer is zero even at full load?

  1. Core loss
  2. Friction loss
  3. Eddy current loss
  4. Hysteresis loss
Answer
Answer. b

259. In a power transformer, at full load, the efficiency is

  1. Minimum
  2. Maximum
  3. Half the normal efficiency
  4. 20% of the maximum efficiency
Answer
Answer. b

260. A transformer having a turn ratio 1 : 5 and a resistance of 1000 Ω is connected across the secondary terminals, the resistance to the current flowing in the primary will be

  1. 10 Ω
  2. 20 Ω
  3. 40 Ω
  4. 60 Ω
Answer
Answer. c
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