MCQOPTIONS
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MCQOPTIONS
This section includes 14 Mcqs, each offering curated multiple-choice questions to sharpen your Transformers knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
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» D. 99.12% | |
| 2. |
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» B. 9.87 kW | |
| 3. |
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» C. 14.57 kW | |
| 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» D. Cannot be determined | |
| 5. |
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» D. 16/9 | |
| 6. |
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» D. Can t comment | |
| 7. |
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 |
| Answer» B. Iron loss is increased considerably | |
| 8. |
For a transformer given, operating at constant load current, maximum efficiency will occur at ______ |
| A. | 0.8 leading power factor |
| B. | 0.8 lagging power factor |
| C. | Zero power factor |
| D. | Unity power factor |
| Answer» E. | |
| 9. |
Power transformers other than distribution transformers are generally designed to have maximum efficiency around ______ |
| A. | No-load |
| B. | Half-load |
| C. | Near full-load |
| D. | 10% overload |
| Answer» D. 10% overload | |
| 10. |
At which load condition maximum efficiency of a distribution transformer will be achieved? |
| A. | At no load |
| B. | At 60% full load |
| C. | At 80% full load |
| D. | At full load |
| Answer» C. At 80% full load | |
| 11. |
Normal transformers are designed to have maximum efficiency at ___________ |
| A. | Nearly full load |
| B. | 70% full load |
| C. | 50% full load |
| D. | No load |
| Answer» B. 70% full load | |
| 12. |
On which factors transformer routine efficiency depends upon? |
| A. | Supply frequency |
| B. | Load current |
| C. | Power factor of load |
| D. | Load current and power factor of load |
| Answer» E. | |
| 13. |
Efficiency of a power transformer is near to the ___________ |
| A. | 100 per cent |
| B. | 98 per cent |
| C. | 50 per cent |
| D. | 25 per cent |
| Answer» C. 50 per cent | |
| 14. |
When will be the efficiency of a transformer maximum? |
| A. | Copper losses = hysteresis losses |
| B. | Hysteresis losses = eddy current losses |
| C. | Eddy current losses = copper losses |
| D. | Copper losses = iron losses |
| Answer» E. | |