MCQOPTIONS
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MCQOPTIONS
This section includes 11 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. |
The DC machines are designed with flat topped flux density waves because _______________ |
| A. | average value of brush voltage is more for a flat topped B-wave |
| B. | average value of brush voltage is less for a flat topped B-wave |
| C. | losses for flat topped B-wave are less |
| D. | none of the mentioned |
| Answer» B. average value of brush voltage is less for a flat topped B-wave | |
| 2. |
A 6 pole machine is rotating at a speed of 1200rpm. This speed in mechanical rad/sec and electrical radians per second is respectively? |
| A. | 40 , 40 /3 |
| B. | 120 , 40 |
| C. | 20 , 60 |
| D. | 40 , 120 |
| Answer» E. | |
| 3. |
If the dimensions of all the parts of a synchronous generator and the number of field and armature turns are doubled, then the generated voltage will change by a factor of ________ |
| A. | 1 |
| B. | 2 |
| C. | 4 |
| D. | 8 |
| Answer» E. | |
| 4. |
In an alternator, frequency per revolution is equal to ___________ |
| A. | number of poles |
| B. | twice the number of poles |
| C. | speed in rps |
| D. | number of pole-pairs |
| Answer» E. | |
| 5. |
If the rotor of an induction motor is made to revolve in a direction opposite to the rotating flux wave, then RMS value of EMF induced in one phase of rotor E is proportional to ____________ |
| A. | 2-s |
| B. | s |
| C. | 1-s |
| D. | 2+s |
| Answer» B. s | |
| 6. |
The equation for slip speed is ____________ |
| A. | ( - <sub>r</sub>)/ |
| B. | - <sub>r</sub> |
| C. | ( <sub>r</sub>- )/ |
| D. | <sub>r</sub> |
| Answer» C. ( <sub>r</sub>- )/ | |
| 7. |
A polyphase induction motor of the slip ring or wound rotor type can be used ____________ |
| A. | for high start-up torque applications |
| B. | as a frequency converter |
| C. | any of the mentioned |
| D. | none of the mentioned |
| Answer» D. none of the mentioned | |
| 8. |
In an AC machine, the effect of distributing the turns in different slots, results in a further reduction of generated EMF by the factor kd. This factor is called ____________ |
| A. | distribution/speed factor |
| B. | coil pitch factor |
| C. | winding factor |
| D. | all of the mentioned |
| Answer» B. coil pitch factor | |
| 9. |
In AC rotating machines, the generated or speed EMF ___________ |
| A. | leads by 90 |
| B. | lags by 90 |
| C. | is in phase with working flux |
| D. | lags by 180 |
| Answer» C. is in phase with working flux | |
| 10. |
In the equation for RMS value of the generated EMF in a full pitched coil of an AC machine, E = Emax/ 2 = 2 frN , fr depends on ____________ |
| A. | rotating speed of the armature coil |
| B. | rotating speed of the flux density wave |
| C. | relative velocity between the flux density wave and armature coil |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| 11. |
The EMF equation e = N r sin rt is applicable to ____________ |
| A. | AC systems with time variant field flux |
| B. | DC systems with time variant field flux |
| C. | Both AC and DC systems with time invariant field flux |
| D. | Both AC and DC systems with time variant field flux |
| Answer» D. Both AC and DC systems with time variant field flux | |