1. The turn ratio of a 220 V AC to 24 V AC step down transformer must be
(a) 9.1.
(b) 5.13.
(c) 0.109.
(d) 0.513.
Answer
2. Which of the following loss in a transformer is zero even at full load ?
(a) Core loss.
(b) Friction loss.
(c) Eddy current loss.
(d) Hysteresis loss.
Answer
3. When the full load of a transformer is reduced to half full load, its copper losses are
(a) reduced by half.
(b) reduced by four time.
(c) remain unchanged.
(d) double.
Answer
4. When the full load of a transformer is reduced to half full load, the iron losses are
(a) reduce by half
(b) reduce by four time
(c) remain same
(d) double
Answer
5. The hum in a transformer is mainly attributed to
(a) load changes.
(b) oil in the transformer.
(c) magnetostriction.
(d) mechanical vibrations.
Answer
6. In which transformer, the territory winding is used?
(a) star delta.
(b) delta star.
(c) delta delta.
(d) star star.
Answer
7. A no-load test on a transformer is conducted to determine
(a) core loss.
(b) copper loss.
(c) efficiency.
(d) magnetising current and loss.
Answer
8. The primary and secondary winding of an auto-transformer are
(a) electrically coupled.
(b) magnetically coupled.
(c) both of the above.
(d) none of the above.
Answer
9. The no load current in a transformer lags behind the applied voltage by an angle of about
(a) 180°.
(b) 90°.
(c) 75°.
(d) 30°.
Answer
10. In the circuit model of transformer the copper loss can be represented as
(a) series resistance.
(b) shunt resistance.
(c) shunt inductance.
(d) series inductance.
Answer
11. The main function of conservator in a transformer is to
(a) provide fresh air to transformer.
(b) supply cooling oil to transformer.
(c) protect the transformer from damage when oil expends due to heating.
(d) absorb moisture from air.
Answer
12. Auto transformer can be good choice if the transformation ratio is
(a) more than one.
(b) near to one.
(c) less than one.
(d) near to zero.
Answer
13. Transformer breaths in when
(a) load on it increases..
(b) load on it decreases.
(c) load remains constant.
(d) none of the above.
Answer
14. An ideal transformer does not change
(a) voltage.
(b) power.
(c) current.
(d) all of the above.
Answer
15. When the leakage flux in a transformer is increases, its secondary induce e.m.f. is
(a) decreases.
(b) increases.
(c) remain same.
(d) none of the above.
Answer