1. The basic function of a transformer is to change
a) the level of the voltage.
b) the power level
c) the power factor
d) the frequency
ans: a
2. In an ordinary transformer which of the following does not change
a) voltage
b) current
c) frequency
d) all the above
ans: c
3. The efficiency of a power transformer is around
a) 50%
b) 60%
c) 80%
d) 95%
ans: d
4. An ideal transformer does not change
a) voltage
b) power
c) current
d) none of the above
ans: b
5. For an ideal transformer the winding's should have
a) maximum resistance on primary side and least resistance on secondary side
b) least resistance on primary side and maximum resistance on the secondary side
c) equal resistance on primary and secondary sides
d) no ohmic resistance on either side
ans: d
6. The core flux in transformer depends mainly on
a) supply voltage
b) supply voltage and frequency
c) supply voltage, frequency and load
d) supply voltage and load but independent of frequency
ans: b
7. A transformer steps up the voltage by a factor 100. The ratio of current in the primary to that in the secondary is
a) 1
b) 100
c) 0.01
d) 0.1
ans: b
8. If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced 50% , the maximum core flux density will
a) change to three times the original value.
b) change to 1.5 times the original value
c) change to 0.5 times the original value
d) remain the same as the original value
ans: a
9. If the supply frequency of a transformer is increased , keeping the supply voltage constant, then
a) both magnetizing component and core loss component of current will decrease
b) both magnetizing component and core loss component of current will increase
c) magnetizing component of current will increase while core loss component of current will decrease
d) magnetizing component of current will decrease while core loss component of current will increase.
ans: a
10. Primary winding of a transformer comprises of two identical winding's in parallel. If one winding's is removed , magnetizing current will be
a) halved
b) the same
c) double
d) increased four times
ans: c
a) the level of the voltage.
b) the power level
c) the power factor
d) the frequency
ans: a
2. In an ordinary transformer which of the following does not change
a) voltage
b) current
c) frequency
d) all the above
ans: c
3. The efficiency of a power transformer is around
a) 50%
b) 60%
c) 80%
d) 95%
ans: d
4. An ideal transformer does not change
a) voltage
b) power
c) current
d) none of the above
ans: b
5. For an ideal transformer the winding's should have
a) maximum resistance on primary side and least resistance on secondary side
b) least resistance on primary side and maximum resistance on the secondary side
c) equal resistance on primary and secondary sides
d) no ohmic resistance on either side
ans: d
6. The core flux in transformer depends mainly on
a) supply voltage
b) supply voltage and frequency
c) supply voltage, frequency and load
d) supply voltage and load but independent of frequency
ans: b
7. A transformer steps up the voltage by a factor 100. The ratio of current in the primary to that in the secondary is
a) 1
b) 100
c) 0.01
d) 0.1
ans: b
8. If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced 50% , the maximum core flux density will
a) change to three times the original value.
b) change to 1.5 times the original value
c) change to 0.5 times the original value
d) remain the same as the original value
ans: a
9. If the supply frequency of a transformer is increased , keeping the supply voltage constant, then
a) both magnetizing component and core loss component of current will decrease
b) both magnetizing component and core loss component of current will increase
c) magnetizing component of current will increase while core loss component of current will decrease
d) magnetizing component of current will decrease while core loss component of current will increase.
ans: a
10. Primary winding of a transformer comprises of two identical winding's in parallel. If one winding's is removed , magnetizing current will be
a) halved
b) the same
c) double
d) increased four times
ans: c
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