MCQOPTIONS
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MCQOPTIONS
This section includes 17 Mcqs, each offering curated multiple-choice questions to sharpen your Dc Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
400-V dc shunt motor takes a current of 5.6 A on no-load and 68.3 A on full-load. Armature reaction weakens the field by 3%. What is the ratio of full-load speed to no-load speed? Given: Ra = 0.18 Ω, brush voltage drop= 2 V, Rf = 200 Ω. |
| A. | 1.2 |
| B. | 0.8 |
| C. | 1.4 |
| D. | 1 |
| Answer» E. | |
| 2. |
For speed x rpm, we get field current If1 and for speed y rpm, we get the field current If2. If y is greater than x then, ________________ |
| A. | If1 f2 |
| B. | If1 >If2 |
| C. | If1 =If2 |
| D. | Cannot comment on If1, If2 |
| Answer» C. If1 =If2 | |
| 3. |
Working range of the speed-torque characteristic, with increasing speed will ___________ |
| A. | Reduce |
| B. | Increase |
| C. | Remain same |
| D. | Cannot comment |
| Answer» B. Increase | |
| 4. |
Where will speed-torque characteristics will lie when armature reaction is considered? |
| A. | Below the speed-torque characteristics when armature reaction is not considered |
| B. | Above the speed-torque characteristics when armature reaction is not considered |
| C. | On the speed-torque characteristics when armature reaction is not considered |
| D. | Can be anywhere with the speed-torque characteristics when armature reaction is not considered |
| Answer» C. On the speed-torque characteristics when armature reaction is not considered | |
| 5. |
WHERE_WILL_SPEED-TORQUE_CHARACTERISTICS_WILL_LIE_WHEN_ARMATURE_REACTION_IS_CONSIDERED??$ |
| A. | Below the speed-torque characteristics when armature reaction is not considered |
| B. | Above the speed-torque characteristics when armature reaction is not considered |
| C. | On the speed-torque characteristics when armature reaction is not considered |
| D. | Can be anywhere with the speed-torque characteristics when armature reaction is not considered |
| Answer» C. On the speed-torque characteristics when armature reaction is not considered | |
| 6. |
For speed x rpm, we get field current If1 and for speed y rpm, we get the field current If2. If y is greater than x then, ________________$ |
| A. | I<sub>f1</sub> <i><sub>f2</sub> |
| B. | I<sub>f1</sub> >I<sub>f2</sub> |
| C. | I<sub>f1</sub> =I<sub>f2</sub> |
| D. | Cannot comment on I<sub>f1</sub>, I<sub>f2</sub> |
| Answer» C. I<sub>f1</sub> =I<sub>f2</sub> | |
| 7. |
Working_range_of_the_speed-torque_characteristic,_with_increasing_speed_will____________$ |
| A. | Reduce |
| B. | Increase |
| C. | Remain same |
| D. | Cannot comment |
| Answer» B. Increase | |
| 8. |
In which of the following method, effect of armature reaction is more? |
| A. | Field weakening method |
| B. | Armature resistance control |
| C. | Same in both methods |
| D. | Cannot be determined |
| Answer» B. Armature resistance control | |
| 9. |
400-V dc shunt motor takes a current of 5.6 A on no-load and 68.3 A on full-load. Armature reaction weakens the field by 3%. What is the ratio of full-load speed to no-load speed? Given: Ra = 0.18 Ω, brush voltage drop= 2 V, Rf = 200 Ω.$ |
| A. | 1.2 |
| B. | 0.8 |
| C. | 1.4 |
| D. | 1 |
| Answer» E. | |
| 10. |
Speed regulation of a DC shunt motor is equal to 10%, at no load speed of 1400 rpm. What is the full load speed? |
| A. | 1233 rpm |
| B. | 1273 rpm |
| C. | 1173 rpm |
| D. | 1123 rpm |
| Answer» C. 1173 rpm | |
| 11. |
No load speed of the DC shunt motor is 1322 rpm while full load speed is 1182 rpm. What will be the speed regulation? |
| A. | 12.82 % |
| B. | 11.8 % |
| C. | 16.6 % |
| D. | 14.2 % |
| Answer» C. 16.6 % | |
| 12. |
Which speeds can be obtained from field control of DC shunt motor? |
| A. | Lower than rated speeds |
| B. | Greater than rated speeds |
| C. | Lower and greater than rated speeds |
| D. | Neither lower nor greater than rated speeds |
| Answer» C. Lower and greater than rated speeds | |
| 13. |
Speed regulation of DC shunt motor is calculated by ratio of difference of full load speed and no-load speed with full load speed. |
| A. | True |
| B. | False |
| Answer» C. | |
| 14. |
The speed of a DC shunt motor can be made more than full load speed by __________ |
| A. | Reducing the field current |
| B. | Decreasing the armature current |
| C. | Increasing the armature current |
| D. | Increasing the excitation current |
| Answer» B. Decreasing the armature current | |
| 15. |
If the speed of a DC shunt motor is increased, the back emf of the motor will ___________ |
| A. | Increase |
| B. | Decrease |
| C. | Remain same |
| D. | Become zero |
| Answer» B. Decrease | |
| 16. |
What will happen if excitation of DC shunt motor is changed? |
| A. | Torque will remain constant |
| B. | Torque and power both will change |
| C. | Torque will change but power will remain constant |
| D. | Torque, power and speed, all will change |
| Answer» D. Torque, power and speed, all will change | |
| 17. |
The speed of a DC shunt motor can be increased by ______ |
| A. | Increasing the resistance in armature circuit |
| B. | Increasing the resistance in field circuit |
| C. | Reducing the resistance in the field circuit |
| D. | Reducing the resistance in the armature circuit |
| Answer» C. Reducing the resistance in the field circuit | |