MCQOPTIONS
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MCQOPTIONS
This section includes 9 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
The efficiency of a transformer can be calculated accurately from ___________ |
| A. | Open circuit test, Short circuit test |
| B. | Open circuit test, Short circuit test, Sumpner s test |
| C. | Sumpner s test |
| D. | load test |
| Answer» B. Open circuit test, Short circuit test, Sumpner s test | |
| 2. |
Core losses of a transformer as a function of frequency is best approximated by which of the below characteristics? |
| A. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13a.png"><img alt="The core losses of a transformer as a function of frequency - option a" class="alignnone size-full wp-image-161188" height="217" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13a.png" width="300"/></a> |
| B. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13b.png"><img alt="The core losses of a transformer as a function of frequency - option b" class="alignnone size-full wp-image-161189" height="235" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13b.png" width="300"/></a> |
| C. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13c.png"><img alt="The core losses of a transformer as a function of frequency - option c" class="alignnone size-full wp-image-161190" height="209" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13c.png" width="300"/></a> |
| D. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13d.png"><img alt="The core losses of a transformer as a function of frequency - option d" class="alignnone size-full wp-image-161191" height="205" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13d.png" width="177"/></a> |
| Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13b.png"><img alt="The core losses of a transformer as a function of frequency - option b" class="alignnone size-full wp-image-161189" height="235" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-transformer-losses-efficiency-q13b.png" width="300"/></a> | |
| 3. |
The full load voltage drop in a 1-phase transformer is 2% and 4% respectively due to resistance and leakage reactance. Then the voltage drop is zero at __________ |
| A. | 0.45 lagging |
| B. | 0.45 leading |
| C. | 0.9 lagging |
| D. | 0.9 leading |
| Answer» D. 0.9 leading | |
| 4. |
The full load voltage drop in a 1-phase transformer is 2% and 4% respectively due to resistance and leakage reactance. Then the voltage drop is maximum at __________ |
| A. | 0.45 lagging |
| B. | 0.45 leading |
| C. | 0.9 lagging |
| D. | 0.9 leading |
| Answer» B. 0.45 leading | |
| 5. |
The load current at which maximum efficiency occurs is independent of the load power factor. |
| A. | True |
| B. | False |
| Answer» C. | |
| 6. |
The efficiency of a 20 KVA, 2000/200 V, single phase transformer at unity pf is 98%. The given total losses at full load is 200 W. The pu resistance is? |
| A. | 0.01 |
| B. | 0.1 |
| C. | 1.0 |
| D. | 0.0196 |
| Answer» B. 0.1 | |
| 7. |
The efficiency of a 20 KVA, 2000/200 V, single phase transformer at unity pf is 98%. The total losses at this condition is? |
| A. | 408W |
| B. | 4.08kW |
| C. | 204W |
| D. | 2.04kW |
| Answer» B. 4.08kW | |
| 8. |
It is possible to attain maximum efficiency in a transformer when the ______ |
| A. | core losses are equal to rated full load copper losses |
| B. | core losses are more than rated full load copper losses |
| C. | core losses and full load copper losses are constant |
| D. | copper loss also becomes constant |
| Answer» B. core losses are more than rated full load copper losses | |
| 9. |
Which of the following mentioned losses occur in a transformer? |
| A. | Hysteresis losses; Eddy current losses; Dielectric losses; Stray load losses |
| B. | Hysteresis losses; Eddy current losses; |
| C. | Dielectric losses; Stray load losses |
| D. | Hysteresis losses; Eddy current losses; Stray load losses |
| Answer» B. Hysteresis losses; Eddy current losses; | |