MCQOPTIONS
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MCQOPTIONS
This section includes 10 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. |
For a dc machine, its commutator has a diameter of 50 c rotating at 1000 rpm. For a brush width of 1 cm, the time commutation taken by the machine will be _________ |
| A. | 0.382 ms |
| B. | 0.456 ms |
| C. | 0.573 ms |
| D. | 0.312 ms |
| Answer» B. 0.456 ms | |
| 2. |
A dc machine is run at rated speed in forward direction and then in backward direction. It is observed that, speeds of the rotation are different, then it leads to the conclusion of _________ |
| A. | incorrect brush placement |
| B. | incorrect pole and core alignment |
| C. | incorrect field supply |
| D. | all of the mentioned |
| Answer» B. incorrect pole and core alignment | |
| 3. |
If the students give a forward shift of 10 to the dc generator, then it _________ |
| A. | reduces flux per pole |
| B. | improves flux per pole |
| C. | increases the flux density in core |
| D. | none of the mentioned |
| Answer» B. improves flux per pole | |
| 4. |
The post effects of the armature reaction is _________ |
| A. | main field distortion |
| B. | shift in MNA |
| C. | reduction in main field |
| D. | none of the mentioned |
| Answer» E. | |
| 5. |
The effect of fringing increases as we _________ |
| A. | increase air gap |
| B. | decrease air gap |
| C. | increase in flux density |
| D. | introduce more ferric core material |
| Answer» B. decrease air gap | |
| 6. |
Thyristor controlled starter is preferred over DOL starter due to _________ |
| A. | lesser losses |
| B. | controlled direction |
| C. | least resistance offered |
| D. | all of the mentioned |
| Answer» B. controlled direction | |
| 7. |
How does the speed build up takes place in a dc motor with time? |
| A. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7a.png"><img alt="The speed build up takes place in a dc motor with time - option a" class="alignnone size-full wp-image-160856" height="218" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7a.png" width="300"/></a> |
| B. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7b.png"><img alt="The speed build up takes place in a dc motor with time - option b" class="alignnone size-full wp-image-160857" height="214" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7b.png" width="300"/></a> |
| C. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7c.png"><img alt="The speed build up takes place in a dc motor with time - option c" class="alignnone size-full wp-image-160858" height="205" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7c.png" width="300"/></a> |
| D. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7d.png"><img alt="The speed build up takes place in a dc motor with time - option d" class="alignnone size-full wp-image-160859" height="221" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7d.png" width="300"/></a> |
| Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7b.png"><img alt="The speed build up takes place in a dc motor with time - option b" class="alignnone size-full wp-image-160857" height="214" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q7b.png" width="300"/></a> | |
| 8. |
The shunt motor starters that can be used is/are ___________ |
| A. | 3-point and 4-point starter |
| B. | 5-point starter |
| C. | 4-point starter |
| D. | 5-point and 3-point starter |
| Answer» B. 5-point starter | |
| 9. |
Which of the following express the starting current nature of the dc motor? |
| A. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4a.png"><img alt="The following express the starting current nature of the dc motor - option a" class="alignnone size-full wp-image-160852" height="230" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4a.png" width="300"/></a> |
| B. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4b.png"><img alt="The following express the starting current nature of the dc motor - option b" class="alignnone size-full wp-image-160853" height="217" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4b.png" width="300"/></a> |
| C. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4c.png"><img alt="The following express the starting current nature of the dc motor - option c" class="alignnone size-full wp-image-160854" height="221" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4c.png" width="300"/></a> |
| D. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4d.png"><img alt="The following express the starting current nature of the dc motor - option d" class="alignnone size-full wp-image-160855" height="219" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4d.png" width="300"/></a> |
| Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4b.png"><img alt="The following express the starting current nature of the dc motor - option b" class="alignnone size-full wp-image-160853" height="217" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-motor-starting-q4b.png" width="300"/></a> | |
| 10. |
Considering a human handed control system for the dc motor speed control, if the resistance wire cut out too slowly, then the _____________ |
| A. | starting resistance would burn |
| B. | field winding would burn |
| C. | speed will rise steeply |
| D. | any of the mentioned |
| Answer» B. field winding would burn | |