1. If the input frequency of a transformer is increases then its secondary induced emf
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] A [/accordion-item][/accordion]
2. The main purpose of using shell type transformer is to reduce
(a) hysteresis losses.
(b) eddy current losses.
(c) magnetic leakage.
(d) size of transformer. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] C [/accordion-item][/accordion]
3. A transformer has full load copper losses of 600 watt, the copper losses at half load will be
(a) 150 watt.
(b) 300 watt.
(c) 600 watt.
(d) 1200 watt. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] A [/accordion-item][/accordion]
4. A transformer has 400 watt iron losses at full load, the iron loss at half load will be
(a) 100 watt.
(b) 200 watt.
(c) 400 watt.
(d) 800 watt. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] C [/accordion-item][/accordion]
5. A Buchholz relay can be installed on
(a) auto-transformers.
(b) air-cooled transformers.
(c) oil cooled transformers.
(d) any of the above. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] C [/accordion-item][/accordion]
6. Which of the following electrical machines have maximum efficiency?
(a) Induction motor.
(b) DC motor ultimate.
(c) Power transformer.
(d) Alternator. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] C [/accordion-item][/accordion]
7. Harmonics in transformer result in
(a) increased core losses.
(b) increased I2R losses.
(c) magnetic interference with communication circuits.
(d) all of the above. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] D [/accordion-item][/accordion]
8. While performing open circuit test on a transformer, the primary is supplied with
(a) rated voltage.
(b) rated current.
(c) reduced voltage.
(d) over voltage. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] A [/accordion-item][/accordion]
9. Which winding of the transformer has less cross-sectional area?
(a) primary winding.
(b) secondary winding.
(c) low voltage winding.
(d) high voltage winding. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] D [/accordion-item][/accordion]
10. With the increase in magnitude of the leakage flux, the magnitude of main flux in the core of transformer is
(a) increases.
(b) decreases.
(c) remain unchanged.
(d) none of the above. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] B [/accordion-item][/accordion]
11. The effect of leakage flux in transformer will result in
(a) more copper losses.
(b) more voltage drop.
(c) less copper losses.
(d) less voltage drop. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] B [/accordion-item][/accordion]
12. When a given transformer is run at its rated voltage but reduced frequency, its
(a) flux density remains unaffected.
(b) iron losses are reduced.
(c) core flux density is reduced.
(d) core flux density is increased. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] D [/accordion-item][/accordion]
13. Which of the following device is used to take up the expansion of oil due to temperature rise?
(a) Breather.
(b) Conservator tank.
(c) Radiator.
(d) Buchholz relay. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] B [/accordion-item][/accordion]
14. Which of the following 3-phase connection of a transformer causes interface with the neighboring communication line?
(a) star-delta.
(b) delta-star.
(c) delta-delta.
(d) star-star. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] D [/accordion-item][/accordion]
15. Ferrite core are used in high frequency transformers because it has
(a) high specific gravity.
(b) high resistance.
(c) low resistance.
(d) low permeability. [accordion clicktoclose=true tag=h4][accordion-item title=”Answer” state=closed] B [/accordion-item][/accordion]