MCQOPTIONS
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MCQOPTIONS
This section includes 657 Mcqs, each offering curated multiple-choice questions to sharpen your Testing Subject knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
The armature of D.C. generator is laminated to |
| A. | reduce the bulk |
| B. | provide the bulk |
| C. | insulate the core |
| D. | reduce eddy current loss |
| Answer» E. | |
| 2. |
For both lap and wave windings, there are as many commutator bars as the number of |
| A. | Slots |
| B. | Armature conductors |
| C. | Winding elements |
| D. | Poles |
| Answer» D. Poles | |
| 3. |
In D.C. generators the pole shoes are fastened to the pole core by |
| A. | Rivets |
| B. | Counter sunk screws |
| C. | Brazing |
| D. | Welding |
| Answer» C. Brazing | |
| 4. |
According to Fleming's right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of |
| A. | Motion of conductor |
| B. | Lines of force |
| C. | Either of the above |
| D. | None of the above |
| Answer» C. Either of the above | |
| 5. |
In a D.C. generator |
| A. | External resistance = internal characteristic armature reaction |
| B. | Internal characteristic = magnetization characteristic ohmic drop |
| C. | External characteristic = magnetization characteristic ohmic drop armature reaction |
| D. | Magnetization characteristic = external characteristic |
| Answer» D. Magnetization characteristic = external characteristic | |
| 6. |
For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f.? |
| A. | Lap winding |
| B. | Wave winding |
| C. | Either of (A) and (B) above |
| D. | Depends on other features of design |
| Answer» C. Either of (A) and (B) above | |
| 7. |
Iron losses in a D.C. machine are independent of variations in |
| A. | Speed |
| B. | Load |
| C. | Voltage |
| D. | Speed and voltage |
| Answer» C. Voltage | |
| 8. |
D.C. generators are connected to the bus-bars or disconnected from them only under the floating condition |
| A. | To avoid sudden loading of the prime mover |
| B. | To avoid mechanical jerk to the shaft |
| C. | To avoid burning of switch contacts |
| D. | All above |
| Answer» E. | |
| 9. |
The e.m.f. generated by a shunt wound D.C. generator is E. Now while pole flux remains constant, if the speed of the generator is doubled, the e.m.f. generated will be |
| A. | E/2 |
| B. | 2E |
| C. | Slightly less than E |
| D. | E |
| Answer» C. Slightly less than E | |
| 10. |
The following constitute short-circuit in the armature winding. |
| A. | Insulation failure between two commutator bars |
| B. | Insulation failure between two turns of a coil |
| C. | Two of more turns of the same coil getting grounded |
| D. | All of the above |
| Answer» E. | |
| 11. |
Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator? |
| A. | Dummy coils |
| B. | Commutator |
| C. | Eye bolt |
| D. | Equalizer rings |
| Answer» C. Eye bolt | |
| 12. |
D.C. generator generally preferred for charging automobile batteries is |
| A. | Series generator |
| B. | Shunt generator |
| C. | Long shunt compound generator |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 13. |
When two D.C. series generators are running in parallel, an equalizer bar is used |
| A. | To increase the speed and hence generated e.m.f. |
| B. | To increase the series flux |
| C. | So that two similar machines will pass approximately equal currents to the load |
| D. | To reduce the combined effect of armature reaction of both machines |
| Answer» D. To reduce the combined effect of armature reaction of both machines | |
| 14. |
Laminations of core are generally made of |
| A. | Case iron |
| B. | Carbon |
| C. | Silicon steel |
| D. | Stainless steel |
| Answer» D. Stainless steel | |
| 15. |
As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C. generator is approximately |
| A. | 40 percent |
| B. | 25 percent |
| C. | 10 percent |
| D. | 5 percent |
| Answer» E. | |
| 16. |
In D.C. generators, current to the external circuit from armature is given through |
| A. | Commutator |
| B. | Solid connection |
| C. | Slip rings |
| D. | None of above |
| Answer» B. Solid connection | |
| 17. |
The critical resistance of the D.C. generator is the resistance of |
| A. | Field |
| B. | Brushes |
| C. | Armature |
| D. | Load |
| Answer» B. Brushes | |
| 18. |
The purpose of providing dummy coils in a generator is |
| A. | To reduce eddy current losses |
| B. | To enhance flux density |
| C. | To amplify voltage |
| D. | To provide mechanical balance for the rotor |
| Answer» E. | |
| 19. |
The rapid wear of brushes takes place due to |
| A. | Abrasion from dust |
| B. | Excessive spring pressure |
| C. | Rough commutator bars |
| D. | All of the above factors |
| Answer» E. | |
| 20. |
If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be |
| A. | Zero |
| B. | Small |
| C. | The same as rated voltage |
| D. | High |
| Answer» B. Small | |
| 21. |
The field coils of D.C. generator are usually made of |
| A. | Mica |
| B. | Copper |
| C. | Cast iron |
| D. | Carbon |
| Answer» C. Cast iron | |
| 22. |
In a D.C. generator the critical resistance can be increased by |
| A. | Increasing its field resistance |
| B. | Decreasing its field resistance |
| C. | Increasing its speed |
| D. | Decreasing its speed |
| Answer» D. Decreasing its speed | |
| 23. |
Fleming's right-hand rule regarding direction of induced e.m.f., correlates |
| A. | Magnetic flux, direction of current flow and resultant force |
| B. | Magnetic flux, direction of motion and the direction of e.m.f. induced |
| C. | Magnetic field strength, induced voltage and current |
| D. | Magnetic flux, direction of force and direction of motion of conductor |
| Answer» C. Magnetic field strength, induced voltage and current | |
| 24. |
A D.C. generator can be considered as |
| A. | Rectifier |
| B. | Prime mover |
| C. | Rotating amplifier |
| D. | Power pump |
| Answer» D. Power pump | |
| 25. |
A series generator can self-excite |
| A. | Only if the load current is zero |
| B. | Only if the load current is not zero |
| C. | Irrespective of the value of load current |
| D. | None of the above |
| Answer» C. Irrespective of the value of load current | |
| 26. |
A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly |
| A. | 150 V |
| B. | 175 V |
| C. | 240 V |
| D. | 290 V |
| Answer» D. 290 V | |
| 27. |
In a level compounded D.C. generator, full load terminal voltage is |
| A. | Negligibly low |
| B. | Equal to no-load terminal voltage |
| C. | More than no-load terminal voltage |
| D. | Less than no-load terminal voltage |
| Answer» C. More than no-load terminal voltage | |
| 28. |
Equalizer rings are required in case armature is |
| A. | Wave wound |
| B. | Lap wound |
| C. | Delta wound |
| D. | Duplex wound |
| Answer» C. Delta wound | |