MCQOPTIONS
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MCQOPTIONS
This section includes 14 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. |
Peak flux density in terms of total flux density is given by _________ |
| A. | ATa (peak) = ATa (total) /P |
| B. | ATa (peak) = ATa (total) *P |
| C. | ATa (peak) = ATa (total) /P*P |
| D. | ATa (peak) = ATa (total) *P2 |
| Answer» B. ATa (peak) = ATa (total) *P | |
| 2. |
Increase in flux density at one end of the pole is less than the decrease at the other end. This is called as ____________ |
| A. | Demagnetizing mmf |
| B. | Cross-magnetizing mmf |
| C. | Anti-magnetizing mmf |
| D. | Magnetizing mmf |
| Answer» B. Cross-magnetizing mmf | |
| 3. |
Armature reaction at 900 to the main field is called as ____________ |
| A. | Demagnetizing mmf |
| B. | Cross-magnetizing mmf |
| C. | Anti-magnetizing mmf |
| D. | Magnetizing mmf |
| Answer» D. Magnetizing mmf | |
| 4. |
In a DC machine brushes are normally located along GNA. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 5. |
In a DC generator, the effect of armature reaction on the main pole flux is to _________ |
| A. | Reduce it |
| B. | Distort it |
| C. | Reverse it |
| D. | Reduce and distort it |
| Answer» E. | |
| 6. |
In DC generator, how armature reaction is produced? |
| A. | Its field current |
| B. | Armature conductors |
| C. | Field pole winding |
| D. | Load current in armature |
| Answer» E. | |
| 7. |
What will happen at poles due to armature reaction in DC generator? |
| A. | Demagnetisation of leading pole tip and magnetisation of trailing pole tip |
| B. | Demagnetisation of trailing pole tip and magnetisation of leading pole tip |
| C. | Demagnetising at the centre of all poles |
| D. | Magnetising at the centre of all poles |
| Answer» B. Demagnetisation of trailing pole tip and magnetisation of leading pole tip | |
| 8. |
What is the reason behind short circuit in armature? |
| A. | Insulation failure between two commutator bars |
| B. | Insulation failure between two turns of a coil |
| C. | Two or more turns of the same coil getting grounded |
| D. | Insulation failure between two commutator bars, two turns of a coil or the same coil getting grounded |
| Answer» E. | |
| 9. |
What is the effect of demagnetizing component of armature reaction? |
| A. | Reduces generator emf |
| B. | Increases armature speed |
| C. | Reduces interpole flux density |
| D. | Results in sparking trouble |
| Answer» B. Increases armature speed | |
| 10. |
Armature reaction of an unsaturated DC machine is (in terms of magnetization) ________ |
| A. | Cross-magnetizing |
| B. | Demagnetizing |
| C. | Magnetizing |
| D. | Cannot be determined |
| Answer» B. Demagnetizing | |
| 11. |
Due to the effect of armature reaction in DC machine, the flux per pole and generated voltage ______ and ________ respectively. |
| A. | Increases, decreases |
| B. | Decreases, decreases |
| C. | Decreases, increases |
| D. | Increases, increases |
| Answer» C. Decreases, increases | |
| 12. |
In a DC machine, the form of flux density distribution (main field only) waveform is __________ |
| A. | Triangular |
| B. | Sinusoidal |
| C. | Saw tooth |
| D. | Trapezoidal |
| Answer» E. | |
| 13. |
In a DC machine, the direct axis is __________ |
| A. | Axes of main poles |
| B. | Axes perpendicular to axes of main poles |
| C. | Not determined from the poles position |
| D. | Can be drawn anywhere |
| Answer» B. Axes perpendicular to axes of main poles | |
| 14. |
In a DC machine, the form of armature mmf waveform is __________ |
| A. | Triangular |
| B. | Sinusoidal |
| C. | Saw tooth |
| D. | Rectangular |
| Answer» B. Sinusoidal | |