TRANSFORMERS MCQs SET 17
1. Why efficiency of a transformer, under heavy loads, is comparatively low?
a) Copper loss becomes high in proportion to the output
b) Iron loss is increased considerably
c) Voltage drop both in primary and secondary becomes large
d) Secondary output is much less as compared to primary input
a) Copper loss becomes high in proportion to the output
b) Iron loss is increased considerably
c) Voltage drop both in primary and secondary becomes large
d) Secondary output is much less as compared to primary input
Answer: a
2. The efficiencies of transformers compared to electric motors of the same power are ___________
a) About the same
b) Much smaller
c) Much higher
d) Can’t comment
2. The efficiencies of transformers compared to electric motors of the same power are ___________
a) About the same
b) Much smaller
c) Much higher
d) Can’t comment
Answer: c
3. A transformer having maximum efficiency at 75% full load will have ratio of iron loss and full load copper loss equal to ___________
a) 4/3
b) 3/4
c) 9/16
d) 16/9
3. A transformer having maximum efficiency at 75% full load will have ratio of iron loss and full load copper loss equal to ___________
a) 4/3
b) 3/4
c) 9/16
d) 16/9
Answer: c
4. What is the correct formula of efficiency of a device?
a) Input /output
b) Output/losses
c) 1- (losses/ (output + losses))
d) Cannot be determined
4. What is the correct formula of efficiency of a device?
a) Input /output
b) Output/losses
c) 1- (losses/ (output + losses))
d) Cannot be determined
Answer: c
5. A 500 kVA transformer is having efficiency of 95% at full load and also at 60% of full load; both at unity power factor. Then Pi is ___________
a) 16.45 kW
b) 9.87 kW
c) 14.57 kW
d) Can’t be calculated
5. A 500 kVA transformer is having efficiency of 95% at full load and also at 60% of full load; both at unity power factor. Then Pi is ___________
a) 16.45 kW
b) 9.87 kW
c) 14.57 kW
d) Can’t be calculated
Answer: b
6. A 500 kVA transformer is having efficiency of 95% at full load and also at 60% of full load; both at unity power factor. Then Pc is ___________
a) 16.45 kW
b) 9.87 kW
c) 14.57 kW
d) Can’t be calculated
6. A 500 kVA transformer is having efficiency of 95% at full load and also at 60% of full load; both at unity power factor. Then Pc is ___________
a) 16.45 kW
b) 9.87 kW
c) 14.57 kW
d) Can’t be calculated
Answer: a
7. For a power transformer operating at full load it draws voltage and current equal to 200 V and 100 A respectively at 0.8 pf. Iron and copper losses are equal to 120 kW and 300kW. What is the efficiency?
a) 86.44%
b) 96.44%
c) 97.44%
d) 99.12%
7. For a power transformer operating at full load it draws voltage and current equal to 200 V and 100 A respectively at 0.8 pf. Iron and copper losses are equal to 120 kW and 300kW. What is the efficiency?
a) 86.44%
b) 96.44%
c) 97.44%
d) 99.12%
Answer: c
8. The highest voltage for transmitting electrical power in India is _______
a) 33 kV
b) 66 kV
c) 132 kV
d) 00 kV
8. The highest voltage for transmitting electrical power in India is _______
a) 33 kV
b) 66 kV
c) 132 kV
d) 00 kV
Answer: d
9. A transformer can have zero voltage regulation at _______
a) Leading power factor
b) Lagging power factor
c) Unity power factor
d) Zero power factor
9. A transformer can have zero voltage regulation at _______
a) Leading power factor
b) Lagging power factor
c) Unity power factor
d) Zero power factor
Answer: a
10. What will happen to a given transformer if it made to run at its rated voltage but reduced frequency?
a) Flux density remains unaffected
b) Iron losses are reduced
c) Core flux density is reduced
d) Core flux density is increased
10. What will happen to a given transformer if it made to run at its rated voltage but reduced frequency?
a) Flux density remains unaffected
b) Iron losses are reduced
c) Core flux density is reduced
d) Core flux density is increased
Answer: d
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