241. The function of oil in a transformer is to provide
- Insulation and cooling
- Protection against lighting
- Protection against short circuit
- Lubrication
242. To conduct sumpners test on a transformer
- Only one transformer is sufficient
- Two identical transformers are needed
- Two unidentical transformers are needed
- At least three transformers are necessary
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
- Remain the same
- Become negative
- Reduce and may even become negative
- Increases
244. Power transformers are designed with
- Low leakage reactances
- High leakage reactances
- High all day efficiency
- Low full load voltage regulation
245. The frequency of ac supply is increased keeping impressed voltage of a transformer constant. Its core loss will
- Increase
- Decrease
- Not change
- Depends upon the design of the transformer
246. The open-circuit test at rated voltage is performed on a transformer to determine its
- Regulation
- Efficiency
- Iron losses
- Copper losses
247. Which of the following prevents the damage to a transformer due to lightning?
- Buchholz relay
- Conservator
- Breather
- Horn gap
248. Step-up transformer increase
- Power
- Power factor
- Frequency
- Voltage
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?
- Core
- Breather
- Transformer oil
- Conservator
250. On which of the following do the eddy current losses depend?
- nature of the material
- maximum flux density
- frequency
- I, II and III
- II and III
- I and II
- I and III
251. Which of the following statement(s) is/are true?
- DC supply can not be used for transformers
- The transformer works on the principle of mutual induction.
- Only I
- Both I and II
- Only II
- Neither I nor II
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.
- 13.4 A
- 16.8 A
- 19.6 A
- 18.2 A
253. An ideal transformer has
- Very high losses
- Very low losses
- Moderate losses
- No losses
254. Which of the following is not a type of construction used for single-phase transformer?
- Core type
- Shell type
- Berry type
- Roof type
255. Copper losses of a transformer are
- Directly proportional to turn ratio
- Inversely proportional to turn ratio
- Inversely proportional to square root of turn ratio
- Directly proportional to square of turn ratio
256. Which of the following statement is true about the windings of a transformer?
- Windings are conductively linked
- Windings are inductively linked
- Windings are not linked at all
- Windings are electrically linked
257. Basically, a booster is a
- Synchronous motor
- Capacitor
- Inductor
- Transformer
258. Which of the following losses in the transformer is zero even at full load?
- Core loss
- Friction loss
- Eddy current loss
- Hysteresis loss
259. In a power transformer, at full load, the efficiency is
- Minimum
- Maximum
- Half the normal efficiency
- 20% of the maximum efficiency
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
- 10 Ω
- 20 Ω
- 40 Ω
- 60 Ω