11. Which loss in a transformer varies significantly with load
a. Hysteresis loss
b. Eddy current loss
c. Copper loss
d. Core loss
12. Voltage remaining constant if the frequency is increased then
a. eddy current losses will decrease
b. hysteresis losses will decrease
c. eddy current losses will remain unchanged
d. hysteresis losses will remain unchanged
13. The power factor in a transformer
a. is always unity
b. is always leading
c. is always lagging
d. depends on the power factor of the load
14. At no load the current taken by a transformer
a. lags behind the applied voltage by 80 degree
b. lags behind the applied voltage by 50 degree
c. leads the applied voltage by 50 degree
d. leads the applied voltage by 80 degree
15. The efficiency of a transformer does not depends on
a. current
b. load
c. power factor
d. all of the above
16. If the secondary of a 1 : 10 step up transformer is connected to the primary of a 1 : 5 step up transformer , the total transformation ratio will be
a. 15
b. 30
c. 50
d. 2500
17. Which of the following transformer will be smallest in size
a. 10 KVA , 50 Hz
b. 10 KVA, 60 Hz
c. 10 KVA, 100 Hz
d. 10 KVA, 200 Hz
18. A 1600 KVA, 200 Hz transformer is operated at 50 Hz its KVA rating shoulb be restricted to
a. 800 KVA
b. 400 KVA
c. 200 KVA
d. 100 KVA
19. A short circuit test on a transformer gives
a. copper losses at full load
b. copper losses at half load
c. iron losses at any load
d. sum of iron losses and copper losses
20. Leakage fluxes in a transformer may be minimised by
a. sectionalizing and interleaving the primary and secondary windings
b. constantly cooling the core
c. under rating the transformer
d. reducing the reluctance of the iron core to the minimum
