Interview Technical Questions

Here are 100+ Technical Questions from Mechanical Engineering for Placements or PSUs interviews.

1. Why we do not use the same technology to start both SI/CI engine?

2. Which one is more efficient? A four-stroke engine or a two-stroke and why?
Ans: The Four-Stroke engine is more efficient primarily Because of the presence of valves which precisely control the flow of charge into the chamber and exit the exhaust gases with proper timing which is hard to achieve by ports in a 2 stroke engine.

4. Why there is no differential in a train. What happens when a train takes a turn?

5. A cantilever beam is loaded at a point on its ends what will be the effect in shear force?

6. Why vehicle does not move when its gear is applied though parked in the slope area?

7. What is the shear force in fluid-particle?

8. How gear ratio helps in power variation?

9. What is the angle of twist in drilling?

10. What is the difference between the impact force and sudden force?

11. How to calculate turbine efficiency?

12. Why centrifugal pump casing is called involutes casing?

13. What will happen if a reciprocating compressor runs the exactly in opposite direction?

14. What is the effect of clearance volume in the performance of air- compressor?

15. What are the advantages and disadvantages of the critical speed of the turbine?

16. What will happen if the oil is mixed with boiler feed water?

17. What is the difference between fans and blowers?

18. What are the protections required to protect the turbine?

19. what is the critical temperature?

20. Air is a bad conductor of heat. Why it becomes hot in summer?

21. How many stages are there in the compressor and in gas turbines?

22. Which is more efficient? A rear-engine Volvo Bus or a Front-engine Volvo Bus? (Engine Capacity is the same for both) why?

23. What is the difference between stress and pressure?

24. What is Boiler HP?

25. What is Auto Dosing?

26. What happens when too much oil is injected in the working cylinder?

27. How many manholes should be there on the boiler? Why?

28. What is used to check the amount & quality of fuel in two-stroke IC engine?

29. Work done in the throttling process is given by which formula?

30. The function of the strainer in the IC engine is?

31. What is the difference between the air pre-heater & air blower?

32. Why the compression ratio of the diesel engine should be high?

33. A vertical plate and a horizontal plate are suspended in an open room. Both are heated to the same temperature. Which one will cool first? Why?

34. What is the color of flame if the boiler is running?

35. Which is the best lubricant-air, oil or water?

36. Tell the octane number in Indian petrol?

37. Difference between enthalpy & entropy?

38. What is the difference between a safety valve and a relief valve?

39. Explain cooling and its types?

40. What is the working principle of air compressor?

41. What is cryogenics and what are its fundamentals?

42. What is the difference between a shaper machine and a planner machine?

43. Why stress relieving of stainless steel is not proffered?

44. What are the advantages of PID controllers compared with those of a PLC?

45. Which two continents are mirror images of each other?

46. Where half nut is used?

47. What is the need for drafting?

48. A turbocharger is driven by.............? and what its speed

49. Why turbocharger used in DG....?

50. The stage below saturation is called?

51. Why is a condenser used in a Rankin cycle?

52. What is a servo motor?

53. Can we use light-duty vehicle axles into the heavy-duty machinery axle? If no then why?

54. Stress-strain diagram for fluid?

55. Where manning formula used?

56. What is the level of documentation for an ISO 9001 certified company?

57. What is backplate in centrifugal pumps and its purpose?

58. Why tires are manufactured in black color?

59. Whether ductile material can fail in a brittle manner? When?

60. On what property can you distinguish material as brittle or ductile?

61. Name fuels used in nuclear power plants?

62. On what thermodynamic cycle nuclear power plant works?

63. How can you increase the efficiency of powerplant without changing in the effort?

64. What is the purpose of the governor in a Diesel engine?

65. Why petrol engines have more power than diesel engines of the same capacity?

66. What is the difference between Torque and Power (layman Idea)?

67. What will be the induced stress in the bar?

68. What is the Difference between Rated Speed and Economic Speed?

69. How to convert from HP to BHP or CC to Bhp please explain?

70. How material no. 2062 will mild steel of density 7.85? What are the other codes?

71. Why petrol engine gives more power than the diesel engine even though the diesel engine has a high compression ratio?

72. What is mean by Resistance welding?

73. Compare Brayton and Otto cycle.

74. Why we have to know the specific frequency of any equipment? does anybody know about specific frequency?

75. What is pulverization?

76. What is the function of an isolator?

77. Why the back wheel of the tractor is bigger than the front wheel?

78. Flow will increase or decrease or remain same?

79. Why Mechanical seal used in Pumps?

80. The ratio of Emissive to absorption power of heat by a body is equal to heat emitted by a perfect black body. Who said the statement?

81. What is colour of flame if the of Halide Torch detects a refrigerant leakage?

82. How can we remove paint from (painted over)plastic or nylon objects without damaging the object?

83. How to calculate or arrive the capacity of a mechanical press?

84. The property of a metal that is determined by the indentation on a metal surface

85. The amount of thickness of the metal sheet that can be welded by ultrasonic welding is?

86. The amount of carbon present in Cast Iron?

87. Numeric control is used for?

88. The amount of moisture that is to be present in wood to be called dry wood is?

89. The pattern material used in Investment casting Process is?

90. What is the use of offset follower in cam? Why and where we have to use this type of follower?

91. What is the use of offset follower in cam? Why and where we have to use this type of follower?

92. State the difference between Forging & Fabrication?

93. What is flange rating?

94. What amount of heat energy loss in ESP?

95. What happen when diesel is injected in petrol engine?

96. What do you mean by property of system?

97. Why joule-Brayton cycle is not suitable for a reciprocating engine?

98. How does “turbulence” differ from swirl?

99. Is octane number beyond 100 is possible?

100. Explain the effect of fuel structure on knocking.

101. Discuss the advantages and disadvantages of LPG as a fuel in S.I. Engine?

102. What is the impact of using throttling device instead of expander in vapour compression cycle?

103. What is moisture choking? Which refrigerants are more prone to it?

104. What is Montreal protocol and why CFCs are being phased out?

105. Why reverse Joule Brayton is used in aircraft refrigeration system?

106. Explain how solar-energy can used in refrigeration system?

107. Is wet bulb temperature a thermodynamic property?

108. What is the utility of comfort chart?

109. How would you decide whether a reciprocating compressor or centrifugal compression is to be used in a refrigerating system?

110. Why smoking is not allowed in the air-conditioned enclosure?

111. Why desert coolers become ineffective in raining season?

112. Why package units are being preferred over central air conditioning system?

113. What is MAPI.

114. What is capital budgetary?

115. What is group technology layout?

116. What is leveling & smoothing in production technology?

117. What is the difference between method study & work measurement?

118. How oil is produced? What is the size of well?

119. Pumps used in drilling procedure and why? Why not centrifugal pump? What if we want high head and high discharge?

120. Use of CNG, LNG, LPG etc.

121. What is FPPPA charge?

122. What is Whilling Charge? 

123. What is preventive maintenances?

Additional Technical Questions

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