MCQOPTIONS
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MCQOPTIONS
This section includes 12 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. |
DC generators are disconnected/connected from/to the busbars only under the floating condition because ____________ |
| A. | To avoid sudden loading of the prime mover |
| B. | To avoid burning of all switch contacts |
| C. | To avoid mechanical jerk to the shaft |
| D. | To avoid sudden loading of the prime mover, burning of all switch contacts and avoid mechanical jerking to the shaft |
| Answer» E. | |
| 2. |
How many poles to be used in DC machine if brushes are placed 4 commutator segments apart for 16 commutator segments? |
| A. | 8 |
| B. | 12 |
| C. | 2 |
| D. | 4 |
| Answer» E. | |
| 3. |
Specific resistance for a brush is given by _________ |
| A. | R = (E * W * T) / (I * L) |
| B. | R = (E * W * I) / (T * L) |
| C. | R = (E * W * I) * (T * L) |
| D. | Doesn t depend on E, W, T, I, L. |
| Answer» B. R = (E * W * I) / (T * L) | |
| 4. |
What is the range of the brush friction coefficients for medium category? |
| A. | 0.40 and above |
| B. | 0.22 to 0.40 |
| C. | 0.11 to 0.22 |
| D. | 0.08 to 0.11 |
| Answer» C. 0.11 to 0.22 | |
| 5. |
Spacing between the brushes for a 4-pole machine in terms of commutator segments is equal to 6. What will be the number of armature slots? |
| A. | 48 |
| B. | 3 |
| C. | 24 |
| D. | 6 |
| Answer» D. 6 | |
| 6. |
Spacing between the brushes for a 4-pole machine in terms of commutator segments for 12 conductor segments is _____ |
| A. | 48 |
| B. | 3 |
| C. | 2 |
| D. | 6 |
| Answer» C. 2 | |
| 7. |
For both lap and wave windings, what is the number of commutator bars equal to? |
| A. | Slots |
| B. | Armature conductors |
| C. | Winding elements |
| D. | Poles |
| Answer» D. Poles | |
| 8. |
Reason behind the rapid wear of brushes is __________ |
| A. | Abrasion from dust |
| B. | Excessive spring pressure |
| C. | Rough commutator bars |
| D. | Abrasion from dust, excessive spring pressure and rough commutator bars |
| Answer» E. | |
| 9. |
How to avoid grooves in the commutation of DC machine with the help of brush? |
| A. | Brushes of opposite polarity should track each other |
| B. | Brushes of same polarity should track each other |
| C. | Brush position has no effect on the commutator grooving |
| D. | Brushes should not track each other |
| Answer» B. Brushes of same polarity should track each other | |
| 10. |
What is the requirement of the good commutation? |
| A. | Brushes should be of proper grade, size and material |
| B. | Brushes should smoothly run in the holders |
| C. | Smooth, concentric commutator properly undercut |
| D. | Brushes should be of proper grade, size, material, run smoothly in the holders and concentric commutator properly undercut |
| Answer» E. | |
| 11. |
The drop in the voltage for which of the following types of brush can be expected to be least? |
| A. | Graphite brushes |
| B. | Carbon brushes |
| C. | Metal graphite brushes |
| D. | Cannot be determined |
| Answer» D. Cannot be determined | |
| 12. |
In a DC generator the ripples in the direct emf generated can be reduced by________ |
| A. | Using conductor of annealed copper |
| B. | Using commutator with large number of segments |
| C. | Using carbon brushes of superior quality |
| D. | Using equalizer rings |
| Answer» D. Using equalizer rings | |