1. The main purpose of performing open circuit test at rated voltage is to measure
a) copper loss
b) core loss
c) total loss
d) insulation resistance
ans. b
2. The short-circuit test in a transformer is used to determine
a) iron loss at any load
b) copper loss at any load
c) hysteresis loss
d) eddy-current loss
ans. b
3. The commercial efficiency of a transformer while on open-circuit is
a) zero
b) maximum
c) either zero or 100 %
d) none of these
ans. a
4. An ideal power transformer will have maximum efficiency at a load such that
a) copper loss is less than iron loss
b) copper loss is equal to iron loss
c) copper loss is higher than iron loss
d) none of these
ans. b
5. The iron-losses of a transformer can be calculated by knowing the weights of
a) core only
b) yokes only
c) copper winding only
d) cores and yokes
ans. d
6. With the increase in supply frequency of a transformer, there is
a) decrease in rating
b) increase in rating
c) no change in rating
d) none of these
ans. b
7. The ordinary efficiency of a given transformer is maximum when
a) it runs at half full-load
b) it runs at full-load
c) its copper loss equals iron loss
d) it runs overload
ans. c
8. In a transformer, the resistance between its primary and secondary should be
a) infinity
b) zero
c) 500 ohms
d) nearly 1 k
ans. a
9. The main purpose of using core in a transformer is to
a) decrease iron losses
b) prevent eddy current loss
c) eliminate magnetic hysteresis
d) decrease reluctance of the common magnetic flux path
ans. d
10. The transformer cores are laminated in order to
a) simplify its construction
b) minimize eddy current loss
c) reduce cost
d) reduce hysteresis loss
ans. b
a) copper loss
b) core loss
c) total loss
d) insulation resistance
ans. b
2. The short-circuit test in a transformer is used to determine
a) iron loss at any load
b) copper loss at any load
c) hysteresis loss
d) eddy-current loss
ans. b
3. The commercial efficiency of a transformer while on open-circuit is
a) zero
b) maximum
c) either zero or 100 %
d) none of these
ans. a
4. An ideal power transformer will have maximum efficiency at a load such that
a) copper loss is less than iron loss
b) copper loss is equal to iron loss
c) copper loss is higher than iron loss
d) none of these
ans. b
5. The iron-losses of a transformer can be calculated by knowing the weights of
a) core only
b) yokes only
c) copper winding only
d) cores and yokes
ans. d
6. With the increase in supply frequency of a transformer, there is
a) decrease in rating
b) increase in rating
c) no change in rating
d) none of these
ans. b
7. The ordinary efficiency of a given transformer is maximum when
a) it runs at half full-load
b) it runs at full-load
c) its copper loss equals iron loss
d) it runs overload
ans. c
8. In a transformer, the resistance between its primary and secondary should be
a) infinity
b) zero
c) 500 ohms
d) nearly 1 k
ans. a
9. The main purpose of using core in a transformer is to
a) decrease iron losses
b) prevent eddy current loss
c) eliminate magnetic hysteresis
d) decrease reluctance of the common magnetic flux path
ans. d
10. The transformer cores are laminated in order to
a) simplify its construction
b) minimize eddy current loss
c) reduce cost
d) reduce hysteresis loss
ans. b
