1. A distribution transformer should be selected on the basis of
a) efficiency
b) all day efficiency
c) voltage regulation
d) none of these
ans. b
2. In a transformer the iron losses do not vary with load current because
a) iron losses are equal to copy losses
b) core flux remain constant
c) core area is constant
d) none of these
ans. b
3. It is economical to use auto-transformer when the transformation ratio is
a) low
b) high
c) neither too high nor too low
d) none of these
ans. a
4. The no load test on a transformer is usually carried out by exciting the low voltage winding because
a) the required power input is low
b) the no load current becomes significant and can be conveniently measured
c) it is not advisable to work on the high voltage side
d) none of these
ans. b
5. During a short circuit test, the iron losses are negligible because
a) the mutual flux is small
b) the power factor is low
c) the current is high
d) none of these
ans. a
6. The transformer principle is based on
a) self-induction
b) mutual-induction
c) electric induction
d) the Lenz law
ans. b
7. Hysteresis loss in a transformer depends upon the
a) applied voltage
b) the type of core material
c) number of laminations
d) reactance of the winding
ans. b
8. What is the efficiency of transformers when compared with that of electrical motors of the same power ?
a) much smaller
b) somewhat smaller
c) about the same
d) much higher
ans. d
9. If in a transformer we double the secondary turns and at the same time reduce the primary voltage by half , then the secondary voltage will
a) he halved
b) be four times as high
c) not change
d) be doubled
ans. c
10. What type of core is used for a high frequency transformer?
a) open iron core
b) closed iron core
c) shell type iron core
d) air core
ans. d
a) efficiency
b) all day efficiency
c) voltage regulation
d) none of these
ans. b
2. In a transformer the iron losses do not vary with load current because
a) iron losses are equal to copy losses
b) core flux remain constant
c) core area is constant
d) none of these
ans. b
3. It is economical to use auto-transformer when the transformation ratio is
a) low
b) high
c) neither too high nor too low
d) none of these
ans. a
4. The no load test on a transformer is usually carried out by exciting the low voltage winding because
a) the required power input is low
b) the no load current becomes significant and can be conveniently measured
c) it is not advisable to work on the high voltage side
d) none of these
ans. b
5. During a short circuit test, the iron losses are negligible because
a) the mutual flux is small
b) the power factor is low
c) the current is high
d) none of these
ans. a
6. The transformer principle is based on
a) self-induction
b) mutual-induction
c) electric induction
d) the Lenz law
ans. b
7. Hysteresis loss in a transformer depends upon the
a) applied voltage
b) the type of core material
c) number of laminations
d) reactance of the winding
ans. b
8. What is the efficiency of transformers when compared with that of electrical motors of the same power ?
a) much smaller
b) somewhat smaller
c) about the same
d) much higher
ans. d
9. If in a transformer we double the secondary turns and at the same time reduce the primary voltage by half , then the secondary voltage will
a) he halved
b) be four times as high
c) not change
d) be doubled
ans. c
10. What type of core is used for a high frequency transformer?
a) open iron core
b) closed iron core
c) shell type iron core
d) air core
ans. d
