MCQOPTIONS
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MCQOPTIONS
This section includes 354 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Which starter does not provide high speed protection to the d.c. shunt motor? |
| A. | Three point starter |
| B. | Four point starter |
| C. | Two point starter |
| D. | None of these |
| Answer» C. Two point starter | |
| 2. |
Which type of rotor is generally used for high speed alternators or turbo alternators? |
| A. | Salient pole type |
| B. | Projected pole type |
| C. | Smooth cylindrical type |
| D. | Both (a) & (b) |
| Answer» D. Both (a) & (b) | |
| 3. |
While carrying out brake tests if the belt snaps, then the motor will |
| A. | Rotate at reduced speed but in forward direction |
| B. | Rotate at increased speed but in forward direction |
| C. | Rotate at reduced speed but in backward direction |
| D. | Rotate at increased speed but in backward direction |
| Answer» C. Rotate at reduced speed but in backward direction | |
| 4. |
While conducting the sumpner’s test, the primaries of the two identical transformers are connected in parallel across the supply. The secondary’s are connected in |
| A. | Parallel |
| B. | Series opposition |
| C. | Both in series and parallel |
| D. | Not connected at all |
| Answer» C. Both in series and parallel | |
| 5. |
While connecting three phase transformer in star-star connection, the terminals of secondaries are wrongly joined. Then the mutual phase angle and magnitude of line to line voltages of secondaries will |
| A. | Equal to 120 degree and equal as before |
| B. | Not equal to 120 degree and different |
| C. | Equal to 120 degree and different |
| D. | None of these |
| Answer» C. Equal to 120 degree and different | |
| 6. |
While delivering an useful power of 20 kW to the full load, a 3 phase, 50 Hz, 6 pole induction motor draws a line current of 50 A. it is connected to supply of 420 V and runs at a speed of 950 rpm. If mechanical losses are 1000 W, then its rotor copper losses and shaft torque are |
| A. | 1105.26 W, 201.03 N-m |
| B. | 1125.26 W, 201.03 N-m |
| C. | 1105.26 W, 208.09 N-m |
| D. | 1125.26 W, 208.09 N-m |
| Answer» B. 1125.26 W, 201.03 N-m | |
| 7. |
While drawing the graph of no load losses versus voltage, the voltage is extrapolated to V = 0. The extrapolated region shows |
| A. | Copper losses |
| B. | Core losses |
| C. | Friction and windage losses |
| D. | None of these |
| Answer» D. None of these | |
| 8. |
While performing retardation tests, the machine whose test is to be taken is run at a speed which is |
| A. | Slightly less than its rated speed |
| B. | Equal to its rated speed |
| C. | Slightly greater than its rated speed |
| D. | All of these |
| Answer» D. All of these | |
| 9. |
While performing Swinburne’s test, the iron losses are assumed to be |
| A. | Constant |
| B. | Absent |
| C. | Variable |
| D. | None of these |
| Answer» B. Absent | |
| 10. |
While performing sumpner’s test on transformer, if the secondary are not in series opposition then the meter will read |
| A. | 0 |
| B. | Twice of the induced emf in each secondary’s |
| C. | Equal to the induced emf in each secondary’s |
| D. | Keep fluctuating |
| Answer» C. Equal to the induced emf in each secondary’s | |
| 11. |
While synchronization of three phase alternators by lamps bright and dark method, if the lamps pair become dark and bright simultaneously, it indicates |
| A. | Incorrect phase sequence |
| B. | That the frequencies of alternators are different |
| C. | That voltage of the alternators are not in phase opposition |
| D. | All of these |
| Answer» B. That the frequencies of alternators are different | |
| 12. |
While using stator resistance starter with 3 phase induction motor, the resistances of the starter are kept at |
| A. | Maximum |
| B. | Minimum |
| C. | Half of the maximum value |
| D. | None of these |
| Answer» B. Minimum | |
| 13. |
Windings of star-delta starter while starting and during running are connected in |
| A. | Star, delta |
| B. | Delta, delta |
| C. | VStar, star |
| D. | Delta, star |
| Answer» B. Delta, delta | |
| 14. |
With a bank of two single phase transformers connected in V - V fashion supplying a balanced three phase load with Cosφ as power factor. The power factor of the two transformers is given by |
| A. | Cosφ , Cosφ |
| B. | Cosφ, Cos(30+φ) |
| C. | Cos(30-φ), Cos(30+φ) |
| D. | Cos(30-φ), Cosφ |
| Answer» D. Cos(30-φ), Cosφ | |
| 15. |
With increase in load, the speed of synchronous motor |
| A. | Increases |
| B. | Decreases |
| C. | Remains constant |
| D. | None of the above |
| Answer» D. None of the above | |
| 16. |
With the increase in temperature, the speed of series and shunt motor will |
| A. | Increase, decrease |
| B. | Decrease, increase |
| C. | Increase, increase |
| D. | Decrease, decrease |
| Answer» C. Increase, increase | |
| 17. |
Yoke in d.c. machine serves the outermost cover. For magnetic flux it provides |
| A. | A low reluctance path |
| B. | A high reluctance path |
| C. | Both (a) & (b) |
| D. | Does not provide path for magnetic flux |
| Answer» B. A high reluctance path | |
| 18. |
Which of the following is not true about induction generator? |
| A. | Synchronization for induction generator is required |
| B. | Induction generators are more suitable for high speeds |
| C. | With the help of excitation supply and frequency, the voltage and frequency of induction motor are controlled |
| D. | The construction is rugged for rotating parts |
| Answer» B. Induction generators are more suitable for high speeds | |
| 19. |
Which motor is not suitable for the application of centrifugal pumps? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Cumulative compound motor |
| D. | Differential compound motor |
| Answer» C. Cumulative compound motor | |
| 20. |
Which method is suitable for the speed control, below and above the normal rated speed of d.c. shunt motor? |
| A. | Flux control method |
| B. | Rheostatic control method |
| C. | Voltage control method |
| D. | All of these |
| Answer» D. All of these | |
| 21. |
Which method for finding percentage regulation in synchronous machines is called pessimistic method? |
| A. | E.M.F. method |
| B. | M.M.F. method |
| C. | Z.P.F. method |
| D. | Direct loading method |
| Answer» B. M.M.F. method | |
| 22. |
Whether the given autotransformer is step up or step down, its VA rating is always |
| A. | Greater than the two winding transformer |
| B. | Equal to the two winding transformer |
| C. | lesser than the two winding transformer |
| D. | cannot say |
| Answer» B. Equal to the two winding transformer | |
| 23. |
When we plot the magnitude of the induced emf against the time, the nature of the induced emf will be |
| A. | Sinusoidal |
| B. | Square |
| C. | Triangular |
| D. | Parabolic |
| Answer» B. Square | |
| 24. |
When the voltage across any two terminals of an armature winding of star connected alternator, then the armature resistance per phase is |
| A. | Half of the resistance observed across any two line terminals |
| B. | 3/2 of the resistance observed across any two line terminals |
| C. | 2/3 of the resistance observed across any two line terminals |
| D. | Same as the resistance observed across any two line terminals |
| Answer» B. 3/2 of the resistance observed across any two line terminals | |
| 25. |
When the torque produced by the induction motor is at its maximum, the slip is given by |
| A. | X2 / R2 |
| B. | (R2 + X2) / X2 |
| C. | R2 / X2 |
| D. | R2 / (R2 + X2) |
| Answer» D. R2 / (R2 + X2) | |
| 26. |
When the slip of an induction machine is negative, it is running as a |
| A. | Motor |
| B. | Generator |
| C. | Synchronous machine |
| D. | None of these |
| Answer» C. Synchronous machine | |
| 27. |
When the induction motor runs faster than the synchronous speed, the induction motor runs as |
| A. | Asynchronous generator |
| B. | Induction generator |
| C. | Synchronous motor |
| D. | Such condition is not possible |
| Answer» C. Synchronous motor | |
| 28. |
When the air gap is smaller in induction motor then its |
| A. | magnetizing current reduces |
| B. | starting torque increases |
| C. | both a and b |
| D. | neither a nor b |
| Answer» B. starting torque increases | |
| 29. |
When stator resistance starter is used, the factor by which stator voltage reduces is say x. If x<1, then due to stator resistance starter, the starting torque |
| A. | Increases by fraction x |
| B. | Reduces by fraction x ∧ 2 |
| C. | Reduces by fraction x |
| D. | Increases by fraction x ∧ 2 |
| Answer» C. Reduces by fraction x | |
| 30. |
When rotor resistance starter is used with induction motor then |
| A. | Only starting current is limited |
| B. | Only starting torque is limited |
| C. | Both starting current and starting torque are limited |
| D. | Neither starting current nor starting torque is limited |
| Answer» D. Neither starting current nor starting torque is limited | |
| 31. |
When an induction motor is working under loaded condition, its induced voltage will |
| A. | Leads the magnetic flux by 90 degree |
| B. | Lags the magnetic flux by 90 degree |
| C. | Lags the magnetic flux by 30 degree |
| D. | In phase with the magnetic flux |
| Answer» C. Lags the magnetic flux by 30 degree | |
| 32. |
When an induction motor is loaded from no load to full load, its speed and slip |
| A. | Increases, decreases |
| B. | Decreases, increases |
| C. | Both increases |
| D. | Both decreases |
| Answer» C. Both increases | |
| 33. |
When an alternator is connected to infinite bus bar, change in excitation for alternator will |
| A. | Change the terminal voltage and power factor both |
| B. | Affect only terminal voltage and power factor remains unaffected |
| C. | Affect only power factor and terminal voltage remains unaffected |
| D. | Neither terminal voltage will get affected nor power factor |
| Answer» D. Neither terminal voltage will get affected nor power factor | |
| 34. |
When a resistance is to be transferred from primary to secondary side of transformer with the turns ratio as k, it must be |
| A. | Multiplied by k ∧ 2 |
| B. | Multiplied by k |
| C. | Divided by k |
| D. | Divided by k ∧ 2 |
| Answer» B. Multiplied by k | |
| 35. |
When a purely capacitive load is connected to the alternator having zero leading power factor then the armature flux and main flux will be |
| A. | In the same direction |
| B. | In the opposite direction |
| C. | Main flux will lead armature flux by 90 degree |
| D. | Main flux will lag armature flux by 90 degree |
| Answer» B. In the opposite direction | |
| 36. |
What happens to the hysteresis losses and eddy current losses, if the frequency of a transformer is increased keeping the supply voltage constant? |
| A. | Both will decrease |
| B. | Hysteresis losses will increase and eddy current losses will decrease |
| C. | Hysteresis losses will remain same and eddy current losses will decrease |
| D. | Hysteresis losses will decrease and eddy current losses will remain same |
| Answer» E. | |
| 37. |
What happens if the number of stator slots in an induction motor is equal to the number of rotor slots or integral multiple of rotor slots? |
| A. | Motor will run at very high speed |
| B. | Motor will run at very low speed |
| C. | Motor will fail to start |
| D. | Does not get effected |
| Answer» D. Does not get effected | |
| 38. |
What happens if dc supply is given to the transformer? |
| A. | Transformer will work more efficiently |
| B. | It will work less efficiently |
| C. | It will work same as with ac supply |
| D. | Not work at all |
| Answer» E. | |
| 39. |
What happens if a stationary alternator is connected to live bus bar? |
| A. | It can result in short circuit |
| B. | A large emf will be induced by alternator |
| C. | Both (a) and (b) |
| D. | None of these |
| Answer» B. A large emf will be induced by alternator | |
| 40. |
What does the pointer of synchroscope indicate when it is rotating in anticlockwise direction and when it is rotating in clockwise direction? |
| A. | Incoming machine is running slow, incoming machine is running faster |
| B. | Incoming machine is running faster, incoming machine is running slow |
| C. | Pointer rotates only in clockwise direction |
| D. | all of the above |
| Answer» B. Incoming machine is running faster, incoming machine is running slow | |
| 41. |
Ward-Leonard system is used for |
| A. | Wide range of speed control |
| B. | Very sensitive speed control |
| C. | Both (a) & (b) |
| D. | None of these |
| Answer» D. None of these | |
| 42. |
Use of an autotransformer is economical when its transformation ratio is |
| A. | Near unity |
| B. | Much greater than unity |
| C. | Much lesser than unity |
| D. | None of these |
| Answer» B. Much greater than unity | |
| 43. |
Under excitation occurs when the magnitude of induced emf of synchronous motor is less than the applied voltage. During under excitation the current drawn by the motor and power factor |
| A. | Increases, decreases and will be lagging in nature |
| B. | Decreases, increases and will be leading in nature |
| C. | Increases, increases and will be leading in nature |
| D. | Decreases, decreases and will be lagging in nature |
| Answer» B. Decreases, increases and will be leading in nature | |
| 44. |
Two transformers are operated in parallel, most essential condition to be satisfied is |
| A. | Polarities should be same |
| B. | Leakage reactance should be equal |
| C. | Turns ratios should be equal |
| D. | Impedances should be in proportion to their kVA rating |
| Answer» B. Leakage reactance should be equal | |
| 45. |
Two 4 pole d.c. machines of identical armature, one with wave winding and other with lap winding are wound. Then |
| A. | The lap wound machine will have more generated voltage |
| B. | Wave wound machine will have more generated voltage |
| C. | Both will have same generated voltage |
| D. | None of these |
| Answer» C. Both will have same generated voltage | |
| 46. |
To perform field test on d.c. machines two motors are required. The motors used are |
| A. | Series motors |
| B. | One will be series motor and other will be shunt motors |
| C. | Shunt motors |
| D. | None of these |
| Answer» B. One will be series motor and other will be shunt motors | |
| 47. |
To minimize the harmonics from the voltage waveform, the suitable steps is / are |
| A. | Using distributed type of winding instead of concentrated type |
| B. | Using fractional slot windings |
| C. | Skewing the pole face |
| D. | All of these |
| E. | None of these |
| Answer» E. None of these | |
| 48. |
To have perfect neutralization of armature mmf under the pole shoe, the ampere conductors of compensating winding must be |
| A. | Not equal to the total armature ampere conductors under the pole shoe |
| B. | Equal to the total armature ampere conductors under the pole shoe |
| C. | Half of the total armature ampere conductors under the pole shoe |
| D. | Twice of the total armature ampere conductors under the pole shoe |
| Answer» C. Half of the total armature ampere conductors under the pole shoe | |
| 49. |
To have d.c. voltage, a device is used in a d.c. generator to convert alternating emf to unidirectional emf. This device is called |
| A. | Armature |
| B. | Commutator |
| C. | Brushes |
| D. | All of these |
| Answer» C. Brushes | |
| 50. |
To have effective synchronization without any interruption, the necessary conditions which must be satisfied are |
| A. | The terminal voltage and frequency of the incoming machine must be same as that of bus bar voltage and frequency |
| B. | With respect to the external load, the phase of alternator voltage must be identical with that of the bus bar voltage |
| C. | Both (a) and (b) |
| D. | None of these |
| Answer» D. None of these | |