MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 29 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A bank of three single phase transformer can be used for obtaining the three phase output. Three magnetic circuits produced in case of a bank of three single phase transformer and in case of single phase transformer are |
| A. | Linked, independent |
| B. | Independent, linked |
| C. | Linked, linked |
| D. | Both are independent |
| Answer» C. Linked, linked | |
| 2. |
A 600kVA transformer has core losses of 1w at 25 Hz and 2.5w at 50 Hz (neglecting resistances and assuming flux density to be constant). The power required at 60 Hz is |
| A. | 3 watt |
| B. | 3.5 watt |
| C. | 3.24 watt |
| D. | 3.54 watt |
| Answer» D. 3.54 watt | |
| 3. |
A 600 kVA transformer has iron losses of 400 kW and copper losses of 500 kW. Its kVA rating for maximum efficiency is given by |
| A. | 537 kVA |
| B. | 548 kVA |
| C. | 555 kVA |
| D. | 585 kVA |
| Answer» B. 548 kVA | |
| 4. |
A 6 pole wave wound d.c. generator has 460 armature conductors carrying armature current of 180 A. The armature reaction demagnetizing and cross magnetizing ampere turns per pole if brushes are shifted by 6 degree electrical from G.N.A are |
| A. | 3220, 230 |
| B. | 3220, 260 |
| C. | 260, 3220 |
| D. | 230, 3220 |
| Answer» E. | |
| 5. |
A 6 kVA, 220 v 3 phase, star connected synchronous generator has a winding resistance of 0.15 ohm per phase and synchronous reactance of 6.1 ohm per phase. The voltage regulation of alternator at a load power factor of 0.8 lagging will be |
| A. | 58.10 % |
| B. | 68.43 % |
| C. | 69.02 % |
| D. | 72.81 % |
| Answer» B. 68.43 % | |
| 6. |
A 5kV / 250V, 50Hz single phase core type transformer with average flux in the core is 0.05wb. The number of turns in the primary winding is |
| A. | 273 |
| B. | 278 |
| C. | 280 |
| D. | 287 |
| Answer» E. | |
| 7. |
A 500 kVA single phase transformer has 90% efficiency at both half load and full load at unity power factor. Then iron losses will be |
| A. | 12.55 KW |
| B. | 13.55 kW |
| C. | 16.55 kW |
| D. | 18.55 KW |
| Answer» E. | |
| 8. |
A 50 Hz, 3 phase slip ring induction motor, has 6 poles on stator and 4 poles on rotor. Then the machine will run at |
| A. | 1000 rpm |
| B. | 1500 rpm |
| C. | 1400 rpm |
| D. | Machine will not run at all |
| Answer» E. | |
| 9. |
A 50 Hz, 3 phase induction motor with 4 pole stator is supplied by mains, which contains a pronounced fifth time harmonic. The speed of the fifth space harmonic will be |
| A. | 100 rpm |
| B. | 300 rpm |
| C. | 600 rpm |
| D. | 7500 |
| Answer» C. 600 rpm | |
| 10. |
A 400v, 4 pole, 3 phase, 50 Hz star connected induction motor has a rotor resistance and reactance per phase equal to 0.02 ohm and 0.2 ohm respectively. Then the slip at which maximum torque occurs and the corresponding maximum torque is (assuming stator to rotor turns ratio as 6) |
| A. | 10%, 159.08 N - m |
| B. | 20%, 318.16 N - m |
| C. | 11%, 159.08 N - m |
| D. | 10%, 318.16 N - m |
| Answer» B. 20%, 318.16 N - m | |
| 11. |
A 4 pole, lap wound d.c. motor drawing an armature current of 20 A has 360 conductors. If the flux per pole is 0.015 Wb then the gross torque developed by the armature of motor is |
| A. | 10.23 N-m |
| B. | 15.56 N-m |
| C. | 17.17 N-m |
| D. | 19.08 N-m |
| Answer» D. 19.08 N-m | |
| 12. |
A 4 pole, lap wound d.c. generators has 40 coils with 8 turns per coils. It is driven at 1200 rpm. If the flux per pole is 0.022 Wb, then the generated emf is |
| A. | 265.8 V |
| B. | 276.3 V |
| C. | 281.6 V |
| D. | 287.9 V |
| Answer» D. 287.9 V | |
| 13. |
A 4 pole d.c. shunt generator having a wave winding supplies 45 lamps, each of 50 W at 100 V. The armature and field resistance are 0.15 ohm and 50 ohm respectively. The current in armature conductor is |
| A. | 11.25 A |
| B. | 11.50 A |
| C. | 12.25 A |
| D. | 13.50 A |
| Answer» D. 13.50 A | |
| 14. |
A 4 pole, d.c. generator has a wave wound armature with 812 conductors. The flux per pole is 0.014 Wb. The speed at which it should be run to generate 240 V on no load is |
| A. | 623.23 rpm |
| B. | 633.35 rpm |
| C. | 643.36 rpm |
| D. | 645.53 rpm |
| Answer» C. 643.36 rpm | |
| 15. |
A 4 pole, 3 phase, 50 Hz star connected induction motor has a full load slip of 5%. Then full load speed of the motor is |
| A. | 1500 |
| B. | 1400 |
| C. | 1405 |
| D. | 1425 |
| Answer» E. | |
| 16. |
A 4 pole, 50 Hz, wound rotor inductor is supplied at rated voltage and frequency with slip ring open circuited. If the rotor is driven by an external means at 1500 rpm opposite to the direction of stator field, the frequency of voltage across slip rings will be |
| A. | 50 Hz |
| B. | 80 Hz |
| C. | 100 Hz |
| D. | 0 Hz |
| Answer» D. 0 Hz | |
| 17. |
A 4 pole, 25 kW, three phase, 420 V, 50 Hz induction motor operates at an efficiency of 90% with a power factor of 0.8 lagging. The current drawn by the motor from the mains is |
| A. | 42.89 A |
| B. | 45.56 A |
| C. | 47.73 A |
| D. | None of these |
| Answer» D. None of these | |
| 18. |
A 4 pole 240 V, d.c. series motor has a wave wound armature with 180 conductors. The armature resistance and the field winding resistance are 0.10 ohm and 0.2 ohm respectively. If the motor is drawing 40 A current at 0.015 Wb flux per pole, then the speed under this condition is |
| A. | 2533.3 rpm |
| B. | 2644.4 rpm |
| C. | 2756.9 rpm |
| D. | 2987.6 rpm |
| Answer» B. 2644.4 rpm | |
| 19. |
A 4 pole, 220 V, 10 H.P, d.c. shunt motor is rotating at a speed of 320 rpm. Then the developed useful torque is |
| A. | 210.647 N-m |
| B. | 215.547 N-m |
| C. | 219.484 N-m |
| D. | None of these |
| Answer» D. None of these | |
| 20. |
A 3 phase star connected synchronous generator having direct axis reactance of 8 ohm and quadrature axis reactance of 6 ohm supplies current of 9 A with phase angle of 20 degree lagging at 415 V. Then its direct axis component of armature current and quadrature axis component of armature current are |
| A. | 8.04 A, 4.04 A |
| B. | 4.04 A, 6.84 A |
| C. | 6.84 A, 8.04 A |
| D. | 4.04 A, 8.04 A |
| Answer» E. | |
| 21. |
A 3 phase induction motor in a short circuit current is equal 3 times of the full load current. If the full load slip is 2%, then the starting torque as a percentage of full load torque is |
| A. | 6% of full load torque |
| B. | 18% of full load torque |
| C. | 36% of full load torque |
| D. | None of these |
| Answer» C. 36% of full load torque | |
| 22. |
A 3 phase, 50 Hz, 8 pole, star connected alternator has 120 slots having 10 conductors per slot. The flux per pole is 0.02 Wb and distributed sinusoidally. The induced emf per phase for full pitch winding is |
| A. | 849.816 V |
| B. | 956.782 V |
| C. | 1046.812 V |
| D. | None of these |
| Answer» B. 956.782 V | |
| 23. |
A 3 phase, 50 Hz squirrel cage induction motor, has 6 poles on stator and 4 poles on rotor. Then the machine will run at |
| A. | 1000 rpm |
| B. | 1500 rpm |
| C. | 1750 rpm |
| D. | Machine will not run |
| Answer» B. 1500 rpm | |
| 24. |
A 240 V, 17 kW d.c. shunt motor draws an armature current of 80 A at full load. The armature and shunt field resistances are 0.2 ohm and 195 ohm respectively. The rotational losses and efficiency of motor at full load is |
| A. | 87.20 % |
| B. | 89.32 % |
| C. | 89.67 % |
| D. | 90.03 % |
| Answer» B. 89.32 % | |
| 25. |
A 220 V, d.c. motor draws an armature current of 20 A. Its armature resistance is 0.6 ohm. Then the induced emf in the motor will be |
| A. | 195 V |
| B. | 202 V |
| C. | 208 V |
| D. | 215 V |
| Answer» D. 215 V | |
| 26. |
A 16 pole, 50 Hz, star connected three phase induction motor has rotor resistance of 0.012 ohm per phase and rotor reactance of 0.220 ohm per phase at standstill. Its full load torque is at speed of 220 rpm. Ratio of its starting torque to maximum torque is |
| A. | 0.1208 |
| B. | 0.1087 |
| C. | 0.1102 |
| D. | 0.1012 |
| Answer» C. 0.1102 | |
| 27. |
A 120 V shunt generator running at 850 rpm has its armature and shunt field resistance of 0.15 ohm and 50 ohm respectively. It supplies 200 lamps each rated at 60 W, 100 V. The friction and windage and core loss of the machine is 400 W. its armature copper loss on full load and shunt field loss is |
| A. | 2156.7 W, 200 W |
| B. | 2232.6 W, 200 W |
| C. | 2156.7 W, 240 W |
| D. | 2232.6 W, 240 W |
| Answer» C. 2156.7 W, 240 W | |
| 28. |
A 120 V d.c. shunt motor runs at speed of 1200 rpm. When the motor is operated unloaded but an additional resistance of 4 ohm is connected in series with the shunt field, then the speed increases and reaches to 1370 rpm with the same terminal voltage. The value of series resistance is |
| A. | 28.23 ohm |
| B. | 32.48 ohm |
| C. | 35.72 ohm |
| D. | 36.82 ohm |
| Answer» B. 32.48 ohm | |
| 29. |
A 10 kVA, 2000 / 100v transformer has R1=1.5 ohm, R2=0.005 ohm, X1=2.5 ohm and X2=0.08 ohm. The equivalent resistance referred to primary is |
| A. | 3 ohm |
| B. | 3.25 ohm |
| C. | 3.5 ohm |
| D. | 3.8 ohm |
| Answer» D. 3.8 ohm | |