MCQOPTIONS
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MCQOPTIONS
This section includes 312 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A 3 phase induction motor is running with full load slip of 1.2% and its rotor impedance per phase is 0.06+j0.265Ω then ratio of starting torque to maximum torque is |
| A. | 0.382 |
| B. | 3.16 |
| C. | 0.123 |
| D. | 0.556 |
| Answer» D. 0.556 | |
| 2. |
For 3phase I.M,the synchronous speed of rotating magnetic field is 750 rpm, slip is 2.5% ,speed of rotor is---------- |
| A. | 500rpm |
| B. | 731.25rpm |
| C. | 1150rpm |
| D. | 300 |
| Answer» C. 1150rpm | |
| 3. |
The conditions of induction motor at no load resembles those of transformer whose secondary is…… |
| A. | short circuited |
| B. | open circuited |
| C. | supplying a variable resistive load |
| D. | none of the above |
| Answer» B. open circuited | |
| 4. |
A 6pole ,3 phase 50Hz I.M is running with 970 rpm. The slip of I.M is |
| A. | 0.03 |
| B. | 0.05 |
| C. | 0.02 |
| D. | 0.01 |
| Answer» B. 0.05 | |
| 5. |
The torque equation of a dc motor is -- |
| A. | ta = 0.159Ø ia/2πpza |
| B. | ta = 0.159Øia/2πza |
| C. | ta = 0.159Øiaz/2πa |
| D. | ta = 0.159Øiapz/a |
| Answer» E. | |
| 6. |
A 3 phase I.M. is running with full load slip of 1.2% and its rotor impedance per phase on standstill is 0.016+j0.265Ω then ratio of full load torque to starting torque is _____. |
| A. | 0.382 |
| B. | 3.16 |
| C. | 0.123 |
| D. | 0.556 |
| Answer» C. 0.123 | |
| 7. |
A 250V DC shunt motor takes a total current of 20A. Resistance of shunt field winding is 200Ω and that of armature is 0.3Ω . What is the current in the armature? |
| A. | 9.65a |
| B. | 11.25a |
| C. | 18.75a |
| D. | 16.62a |
| Answer» D. 16.62a | |
| 8. |
The magnitude of induced emf in a dc generator is given by |
| A. | blv |
| B. | bil |
| C. | bv/l |
| D. | bi/l |
| Answer» B. bil | |
| 9. |
A 3-phase, 4-pole induction motor has a no-load slip of 2% when connnected to a 25 Hz source, the no-load speed in rpm is |
| A. | 730 |
| B. | 735 |
| C. | 765 |
| D. | 1430 |
| Answer» C. 765 | |
| 10. |
A 4 pole, 500V shunt motor has 720 wave connected conductors on its armature. The full load armature current is 60A and flux per pole is 0.03Wb. The armature resistance is 0.2Ω and contact drop per brush is 1V. What is the full load speed of the motor? |
| A. | 675rpm |
| B. | 522rpm |
| C. | 484rpm |
| D. | 576rpm |
| Answer» B. 522rpm | |
| 11. |
A 440V, 20HP, 3phase motor operates at full load, 88% efficiency and 0.65 power factor lagging, the current drawn by motor is |
| A. | 59.28a |
| B. | 0.0458a |
| C. | 34.22 a |
| D. | 26.50a |
| Answer» D. 26.50a | |
| 12. |
Stator windings are insulated from core with the help of |
| A. | slot insulator |
| B. | epoxy coating |
| C. | a or b |
| D. | none |
| Answer» C. a or b | |
| 13. |
A 6pole ,3 phase 50Hz I.M is running with s=3%,runs with |
| A. | 200 |
| B. | 600 |
| C. | 1000 |
| D. | 970 |
| Answer» E. | |
| 14. |
A 4 pole, 250V series motor has a wave connected armature with 1254 conductors. The flux per pole is 22mWb when the motor taking 50A. Iron and friction lossses amount to 1000W. Armature resistance 0.2Ω, series field resistance 0.2Ω. What is the output power in H.P. |
| A. | 14.08hp |
| B. | 21.67hp |
| C. | 9.48hp |
| D. | 11.72hp |
| Answer» B. 21.67hp | |
| 15. |
Stator part of I.M. has slots to hold ------- |
| A. | rotor winding |
| B. | stator winding |
| C. | shaft |
| D. | brush |
| Answer» C. shaft | |
| 16. |
The armature of a 4 pole shunt motor has a lap winding accomodated in 60 slots, each containing 20 conductors, if the useful flux per pole is 23mWb, the armature torque developed when the armature current is 50A is _____. |
| A. | 176nm |
| B. | 192nm |
| C. | 256nm |
| D. | 218nm |
| Answer» E. | |
| 17. |
3 phase I.M. are classified as --- and---- based on rotor construction. |
| A. | slip ring & squirrel cage |
| B. | split phase &squirrel cage |
| C. | capacitor start motor& slip ring |
| D. | shaded pole& capacitor start |
| Answer» B. split phase &squirrel cage | |
| 18. |
For 3phase I.M,the synchronous speed of rotating magnetic field is 1500 rpm,speed of rotor is 1440 rpm ,then slip is |
| A. | 0.01 |
| B. | 0.06 |
| C. | 0.03 |
| D. | 0.04 |
| Answer» E. | |
| 19. |
If the number of poles in a lap wound generator be doubled, then the generated e.m.f will_________. |
| A. | become half |
| B. | become double |
| C. | increase to four times |
| D. | remains constant |
| Answer» C. increase to four times | |
| 20. |
A 220V DC shunt motor takes a total current of 80A and runs at 800 rpm. Resistnace of a shunt field is 50Ω and that of armature 0.1Ω. The iron and friction losses amount to 1600W. What is the lost torque? |
| A. | 11nm |
| B. | 19nm |
| C. | 22nm |
| D. | 34nm |
| Answer» C. 22nm | |
| 21. |
slip of I.M. is given by the formula |
| A. | (ns-n)/ns |
| B. | ns/(ns-n) |
| C. | ns/n |
| D. | (ns-n) |
| Answer» B. ns/(ns-n) | |
| 22. |
The maximum voltage is induced in the rotor of 3-ph induction motor when it---- |
| A. | runs at no load |
| B. | runs at full load |
| C. | is blocked |
| D. | none of the above |
| Answer» B. runs at full load | |
| 23. |
When load is placed in three phase induction motor, its speed |
| A. | decreases |
| B. | increases |
| C. | remains unchanged |
| D. | becomes zero |
| Answer» B. increases | |
| 24. |
An I.M. moror is preferred to a D.C. motor because of its----- |
| A. | high starting torque |
| B. | fine speed control |
| C. | simple and rugged construction |
| D. | none |
| Answer» D. none | |
| 25. |
At any given slip s the rotor induced emf (E2r) is ---- |
| A. | f/e2 |
| B. | f.e2 |
| C. | s.e2 |
| D. | s/e2 |
| Answer» D. s/e2 | |
| 26. |
For I.M. running with 731.25rpm with slip of 2.5%, the synchronous speed of rotating magnetic field |
| A. | 750 |
| B. | 1000 |
| C. | 500 |
| D. | 1500 |
| Answer» B. 1000 | |
| 27. |
A 3 phase induction motor connected from a 3 pjhase, 50Hz AC supply runs at 720rpm and has slip 4%. The number of poles in motor are _____. |
| A. | 4 |
| B. | 6 |
| C. | 8 |
| D. | 16 |
| Answer» D. 16 | |
| 28. |
If the voltage equation of a dc motor is multiplied by ----- on both sides, we get power equation of dc motor |
| A. | ra |
| B. | v |
| C. | n |
| D. | ia |
| Answer» E. | |
| 29. |
In cloth washing machines and refrigerators which motors are preferred? |
| A. | a. dc cumulative compound motors |
| B. | b. slip ring im |
| C. | c. stepper motor |
| D. | d. universal motors |
| Answer» E. | |
| 30. |
What is the flux in the armature core section of a dc machine if the air gap flux be ø Wb? |
| A. | ø |
| B. | 0.1 ø |
| C. | 1.5 ø |
| D. | ø /2 |
| Answer» B. 0.1 ø | |
| 31. |
A squirrel cage induction motor is favoured when ……………….. is the main consideration. |
| A. | initial cost |
| B. | rotor core and rotor teeth |
| C. | stator core and stator teeth |
| D. | stator winding |
| Answer» D. stator winding | |
| 32. |
Which type of motors are preferred in lifts? |
| A. | a. dc compound motors. |
| B. | b. dc series motors. |
| C. | c. dc shunt motors. |
| D. | d. none of the above. |
| Answer» B. b. dc series motors. | |
| 33. |
The field winding of a machine designed for separate excitation is |
| A. | of the shunt field type |
| B. | of the series field type |
| C. | either of the two |
| D. | none of the above |
| Answer» B. of the series field type | |
| 34. |
At any given slip s the rotor reactance is ---- |
| A. | s.x2 |
| B. | s/x2 |
| C. | fr.x2 |
| D. | f.x2 |
| Answer» B. s/x2 | |
| 35. |
A 220V DC series motor is taking a current of 40A. Resistance of armature is 0.5Ω and series field is 0.25Ω. What is the voltage at the brushes? |
| A. | 190v |
| B. | 210v |
| C. | 180v |
| D. | none of the above |
| Answer» C. 180v | |
| 36. |
A 4 pole, 50Hz , 3 phase I M is running at 1425rpm on full load having rotor impedance per phase on standstill as 0.4+j2Ω. The ratio of full load torque to maximum torque is ___. |
| A. | 0.817 |
| B. | 1.223 |
| C. | 0.384 |
| D. | 0.4705 |
| Answer» E. | |
| 37. |
The rotor current in 3-phase I.M. is-----slip |
| A. | inversely proportional to slip |
| B. | directly proportional to slip |
| C. | independent of |
| D. | directly proportional to square of slip |
| Answer» C. independent of | |
| 38. |
A 220V series motor takes a current of 35A and runs at 500rpm. Armature resistance of 0.25Ω and series field resistance 0.3Ω. If iron and frictional losses amount of 600W, what is the armature torque? |
| A. | 122.5nm |
| B. | 118.5nm |
| C. | 134nm |
| D. | 117nm |
| Answer» D. 117nm | |
| 39. |
The counter emf of dc motor__________ |
| A. | often exceeds the supply voltage |
| B. | aids the applied voltage |
| C. | helps in energy conversion |
| D. | regulates its armature voltage |
| Answer» D. regulates its armature voltage | |
| 40. |
The relative speed between stator flux and rotor is equal to |
| A. | synchronous speed , ns |
| B. | rotor speed n |
| C. | zero |
| D. | ns - n |
| Answer» E. | |
| 41. |
A 4 pole, 50Hz , 3 phase I M is running at 1425rpm on full load having rotor impedance per phase on standstill as 0.4+j2Ω. If voltage between the slip rings on open circuit is 520V then the torque developed on full load is ___ Nm. |
| A. | 202.52 |
| B. | 165.53 |
| C. | 430.36 |
| D. | 514.21 |
| Answer» B. 165.53 | |
| 42. |
In planners which of following motors are preferred? |
| A. | a. dc shunt motor |
| B. | b. dc compound motor |
| C. | c. any of above |
| D. | none |
| Answer» D. none | |
| 43. |
----- is the power equation of dc motor |
| A. | via = ebia + ia2 ra |
| B. | via = ebia + ia ra2 |
| C. | vn = eb n + nia ra |
| D. | via = eb2ia + ia2 ra |
| Answer» B. via = ebia + ia ra2 | |
| 44. |
Which of the following parameters of induction motor varies inversely as the supply freq |
| A. | full load speed |
| B. | starting current |
| C. | slip |
| D. | maximum running torque |
| Answer» C. slip | |
| 45. |
The emf equation of dc generator is E= |
| A. | Øp/nza |
| B. | Øp60/nza |
| C. | Øpa/60nz |
| D. | Øpnz/60a |
| Answer» E. | |
| 46. |
Two of the supply terminals to a 3-phase induction motor get interchanged during reconnection after normal maintenance. When switched on to supply, the motor will |
| A. | rotate in the same direction as before maintenance. |
| B. | rotate in a direction opposite to that before maintenance. |
| C. | not start at all. |
| D. | get heated and damaged. |
| Answer» C. not start at all. | |
| 47. |
An 8-pole , 50Hz,3-ph indduction motor running with a slip of 4% is taking 20KW. Stator losses amount 0.5KW. The total torque develped is |
| A. | 248nm |
| B. | 312nm |
| C. | 195nm |
| D. | 214nm |
| Answer» B. 312nm | |
| 48. |
In a dc generator, the eddy current power loss is |
| A. | directly proportional to thickness of each lamination |
| B. | inversely proportional to thickness of each lamination |
| C. | directly proportional to square of thickness of each lamination |
| D. | none of the above |
| Answer» B. inversely proportional to thickness of each lamination | |
| 49. |
The reactance of the rotor circuit of 3-phase I.M. is maxium at |
| A. | no-load |
| B. | full-load |
| C. | half of full load |
| D. | start |
| Answer» E. | |
| 50. |
The armature torque is ------ that of shaft torque |
| A. | less than |
| B. | same as |
| C. | greater than |
| D. | none of these |
| Answer» D. none of these | |