What are some of the best interview questions asked for a mechanical engineering student?

I cleared the BHEL written exam and was called for interview. No GD. Interview was for the post of Executive engineer /E1 grade. It was a 10 minutes interview with 5 persons in the panel.Among them atleast one was an IAS officier.

Vaccant post : called candidates = 1:4 ratio. Loads of question were asked momentarily.Some question I remember are:


1) Take your seat.Why are you sweating? Are you nervous?

No sir. Actually… little bit. This is my first interview for a core company.(They smiled at me).

2) What is an IC engine and how does it work?

Explained from text book knowledge.

3) Difference between petrol engine and diesel engine.Why their milage differs.

Explained properly.

4) What will happen to the room temperature if you turn your room in to a closed system by closing all the door and window perfectly and then you open the door of the room refrigerator that is in running condition.

Got puzzled.but answered as temperature of the room will increase since input is always greater than output of the system.

5)What actually entropy is? Explain me since I know only farming. 😉

I tried to explain entropy as a disorderness of a system without explaning any mathematical formula and interviewer nodded approvingly.

6)Tell me quickly ,Two co-cenric circle rolls together up to 3 mtr.Now tell me whether both the point has travelled same distance or not.


Its the perimeter they are travelling. So obviously different.

7) Explain how a human walks by using friction.What kind of friction is involved (static friction or rolling friction).

Answered though not sure.

8)What is dovetail milling.Why class 3 lever is used in reality.

Explained

9)What is the need of riser in moulding?

Explained riser as a checking process to confirm the molten metal has filled the cavity or not.but interviewer didnot agree indicating me for any other reason.closed my eye and took 5 sec and explained.

riser works as a backup reservior of molten metal when the cavity metal volume shrinks due to solidification.

Interviewer happily agreed.I was like 'God saved'.

10)Gave me a paper and pencil and asked to draw a carnot cycle and explain it.

Explained it.(never forget to give the directional arrow sign for any mechanical cycle.mind it.That is a test too)

11)Asked me bout posting preferences.If it is Ladakh will it be okay for you?

Had to agree by thinking I can drink coffee in the cold ;).Interviewer gave a strange look.

12)Why do you want to quit the biggest IT MNC since this sector is surging?

Told it honestly.Mechanical attracts me more and I will be surging along with BHEL.

After their whispering internal discussion they told "ok.you may leave".


Result: Selected.

There are thousand of question you can be asked to be judged.You need to be thorough with the text books first.Rests are presence of mind and your originality.

All the best.

Edit1: I did not think of so many likes and views (56.2K). It does feel good. Thanks guys.

Hope you get success in career and life ahead.

19 Replies to “What are some of the best interview questions asked for a mechanical engineering student?”

  1. I'm sharing this question list to fellow mechanical engineers that I made to prepare for an interview. It contains two sections viz. technical questions followed by HR questions.

    1. Technical questions:
    Type of technical questions asked will be definition type and that too from basic. Your favorite subjects will be asked first and then they start questioning what they want you to answer.Some of the questions are…

    1. Why we do not use same technology to start both SI/CI engine?
    2. Which one is more efficient? A four stroke engine or a two stroke and why?
    3. 4 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 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 slope area?
    7. What is shear force in fluid particle?
    8. How gear ratio helps in power variation?
    9. What is the angle of twist in drill?
    10. What is the difference between impact force and sudden force?
    11. How to calculate the turbine efficiency?
    12. Why centrifugal pump casing is called involutes casing?
    13. What will happen if reciprocating compressor run in exactly opposite direction?
    14. What is the effect of clearance volume in performance of air- compressor?
    15. What is the advantages and disadvantages of critical speed of turbine?
    16. What will happen if oil is mixed with boiler feed water?
    17. What is difference between fan and blowers?
    18. What are the protections required to protect turbine?
    19. what is critical temperature?
    20. Air is a bad conductor of heat. Why it becomes hot in summer?
    21. How many stages in compressor in there in gas turbine?
    22. Which is more efficient? A rear engine Volvo Bus or a Front engine Volvo Bus? (Engine Capacity is same for both) why?
    23. What is 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 boiler? Why?
    28. What is used to check the amount & quality of fuel in two stroke IC engine?
    29. Work done in throttling process is given by which formula?
    30. Function of the strainer in IC engine?
    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 safety valve and relief valve?
    39. Explain cooling and its types?
    40. What is the working principal 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. Turbo charger driven by………….? and what its speed
    49. Why…? Turbo charger used in DG….?
    50. The stage below saturation is called?
    51. Why is a condenser used in a Rankin cycle?
    52. What is servo motor?
    53. Can we use light duty vehicle axle into the heavy duty machinery axle? If no then why?
    54. Stress strain diagram for fluid?
    55. Where manning formula used?
    56. What is level of documentations for a ISO 9001 certified company?
    57. What is back plate in centrifugal pumps and its purpose?
    58. Why tyres are manufactured in black colour?
    59. Whether ductile material can fail in brittle manner? When?
    60. On what property u can distinguish material as brittle or ductile?
    61. Name fuels used in nuclear power plant?
    62. On what thermodynamic cycle nuclear power plant works?
    63. How can you increase the efficiency of power plant without changing in effort?
    64. What is purpose of governor in Diesel engine?
    65. Why petrol engines have more power than diesel engines of 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 the material no. 2062 will mild steel of density 7.85? What are the other codes?
    71. Why petrol engine gives more power than diesel engine even though diesel engine has 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 tractor is bigger than 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 with out 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 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 deference between method study & work measurement?
    118. What you know about drilling?
    119. How oil is produced? What is the size of well?
    120. Pumps used in drilling procedure and why? Why not centrifugal pump? What if we want high head and high discharge?
    121. Difference between Pipeline and Piping ?
    122. Use of CNG, LNG, LPG etc.
     
    Additional questions subject wise:

    Fluid Mechanics and Fluid Machinery

    • What is the difference between impulse & reaction turbine.
    • Explain unit speed, unit discharge unit power & specific speed.
    • Explain NPSH, in which parameter it depends on.
    • What is jet ratio?
    • What is Deriaz turbine?
    • Which turbine is good for tidal power plant?
    • What is Navier-stroke equation.
    • What are the significance of
    • Mach number
    • Weber number

    Material Science

    • What is quazi-crystal?
    • What do you understand by a free cutting steel? What elements are usually added to make a steel free cutting, & how they make the steel free cutting?
    • Explain various method of hardening of steel?
    • What do you understand by the term “Arrest point” in connecting with heat treatment of plain carbon steel?
    • What influence does grain size have on the mechanical properties of metals.
    • Describe the difference between brittle and ductile fracture.
    • What is the difference between natural & artificial aging?

    Thermodynamics

    • What is availability function for a closed system?
    • If it is possible that entropy of a system can decrease during a given process?
    • What is dead state in thermodynamics?
    • What is exergy?
    • What happens to triple point line when projected to P-T plane?
    • What is compressibility factor and what is its value for Vander walls gases.
    • What are initial conditions for formation of shock waves?
    • What do you understand by choking in nozzle flows?
    • Is it possible that pressure and velocity decreases simultaneously/
    • Distinguish between “Available energy” & Availability?
    • What is pure substances.
    • What is critical point? What is the value f critical temperature, pressure & volume of water?
    • What is sublimation curve, fusion curve & vaporization curve?
    • What is Rayleigh Line & Fanno Line?
    • What is normal shocks & when its occurs?
    • What is High Grade Energy & Low Grade Energy?

    Heat & Mass Transfer

    • What is Newton’s Law of cooling.
    • What is Recuperator & Regenerators?
    • Whether fin can actually reduce heat transfer? is it possible? When?
    • What is difference between Biot no. & Nusselt no?
    • Which one is greater, thermal boundary layer or hydrodynamic boundary layer?
    • What is film temperature in forced convection flow?
    • What is fully developed region and where it is applicable?
    • What is the critical radius of insulation, explain clearly in terms of thermal resistance and heat transfer rate?
    • At what case do you recommend Fin?
    • What is the difference between free convection & forced convection in what parameter forced & free convection depend.

    Internal Combustion Engine

    • What is the use of Carburetor in SI Engine, There is trend towards increases of injection system in Automobiles, Explain.
    • Why Supercharging is not popular with SI Engines?
    • What is performance number.
    • Explain Knocking in SI Engine & Mention, the factor that tend to reduce Knocking?
    • Explain the difference between Knocking in SI Engine & CI Engine?
    • How does “Turbulence” differ from “Swirl”?
    • Name some Antiknock additive and explain the Mechanism by which they reduce the knock?

    Power Plant engineering

    • What is slip ratio in thermal power plant?
    • In Pendant super heater whether parallel flow or counter flow heat exchange between
    • steam and flue gases.
    • What happens to mass flow in case of supersaturated flow?
    • Why clearance are provided in reciprocating compressor?
    • Explain turbojet & Rocket Engine.
    • What’s the advantage of compounding of steam turbine?
    • What’s are boiler mounting & accessory.
    • Draw the sketch of pulse jet engine. What are its main advantage & disadvantage?
    • Explain working principal of scram jet engine, what is advantage over the ramjet?
    • What are the advantage of nuclear power plants over thermal power plants.
    • What is fast breeder reactor?
    • What is circulation ratio and what is its range in power plant?
    • One 2-row Curtis turbine is equivalent to how many reaction turbines for same value of
    • blade velocity and angle of nozzle?
    • What are thermal neutrons?
    • What is breeding ratio?
    • What is the application of jet and rocket technology? Which is used in missiles?

    Strength of Materials

    • What do you mean by equal strength in a beam?
    • What is difference between pure shear and simple (normal) shear?
    • Is it possible that decrease in area gives a decrease in stress?
    • Whether shear stresses are always parallel to shear forces?
    • By which experiment, you find it toughness of material.
    • Distinguish between direct stress & bending stress.
    • What do you mean by Torsional rigidity & lateral rigidity?
    • Define “slenderness ratio”. How it is used in long and short column?

    Machine Design

    • What are rolling contact bearing?
    • What are the anti friction bearings?
    • What is stress concentration factor?
    • What is the bolt of uniform strength?
    • What is the difference Static Load carrying capacity & Dynamic Load carrying capacity?
    • Why we are not using the unit joule for torque instead of N-m.
    • What is Low cycle fatigue failure and High cycle fatigue failure? What are considerations of
    • these while designing a machine?
    • What is mechanical advantage?
    • How trains take turns though there is no differential gear?
    • Do you know epicyclical gear box? What is the practical application of epicyclical gear box?
    • What is tooth profile? Which one is better?

    Theory of Machines

    • What is Keneddy theorem?
    • Do we need a screw with efficiency less than 50%?
    • What is backlash?
    • What is damping ratio?
    • Define Resonance.
    • Define critical speed or whirling speed or whipping speed.
    • What is machine? Giving example, Differentiate between a machine & structure.
    • What is Mechanical advantage.

    Refrigeration and Air-conditioning

    • What is utility of comfort chart?
    • hat is wet compression?
    • To maximize COP what should be the condition of vapour at suction to compression?
    • What is the range of NBP (normal boiling point) in case of most refrigerants?
    • Why COP of CO2 gas is less and still why it is used in transport refrigeration?
    • What are the most crucial parts in reciprocating compressors?
    • How compressors are selected based on type of refrigerant?
    • What is correlation between wet bulb temperatures an adiabatic saturation temperature?
    • Why isothermal compressor is Desirable?
    • What is desirable property of ideal refrigerant?
    • Define effective temperature & what is the optimum design condition for comfort for summer A/C?

    Production Engineering

    • Why arc is slowly extinguished in case of arc welding?
    • Which inert gas is commonly used for thin work piece and which inert gas for thick work piece?
    • What is friction welding?
    • What is difference between brazing & braze welding?
    • Why hole basis system is adopted in manufacturing?
    • What is 3- 2-1 principle?
    • Where diamond pin locator is used?
    • How presses are rated?
    • What is spring back?
    • What is difference between fillet and corner radius?
    • What are overhead costs?
    • Why depreciation is to be taken into account in industrial management?
    • Why breakeven point is important in any industry?
    • What is sine bar?
    • What is marginal cost and marginal revenue?
    • What is shear and where it is provided in case of punching and blanking?
    • What is angle of bite?
    • What is extrusion ratio?
    • What is gutter and where it is used?
    • Which process is used for making nuclear reactor fuel rods?
    • What is difference between Amorphous and crystalline solids?
    • What are the various method of inspection of casting for internal & external defects?
    • Why are allowances provided for in the production of patterns? What do they depend on?
    • What is the deference between soldering & brazing?
    • What is meant by solid-state welding explain.
    • What is cold welding?
    • Describe the principal behind resistance welding processes.
    • What function should a lubricant perform in manufacturing process?
    • Explain the difference between punching & blanking.
    • Explain the difference between discontinuous chips and segment chips.
    • Explain the different type of tool wear.
    • What is difference between oblique & orthogonal cutting.
    • What are the main difference between jig and fixture?
    • What is AOQ
    • What is LTPD
    • What is Producer risk
    • What is Consumer’s risk
    • What is JIT approaches?
    • What is group technology? What are its main advantages?
    • Define the term “production & productivity.
    • What is the significance of ISO 9000 series & 1400 series.
    • What is artificial intelligence?
    • Which welding process does not required any filler material?
    • What is tack weld?
    • Which process used for cutting thicker plates?
    • Where drooping characteristics of power source is required in arc welding?

    2. HR questions:

    1. Tell me about yourself?
    2. What is your hometown famous for?
    3. Tell about your achievements in life.
    4. Your strengths and weakness
    5. Are you a team player?
    6. Tell me about your ability to work under pressure.
    7. How would you know you will be successful on this job?
    8. Describe your management style.
    9. Global warming
    10. Chief justice of India
    11. Vice President of India
    12. CEO of Apple, when did he die?
    13. Gas scenario
    14. RBI policy
    15. Corporate Governance
    16. Corporate Laws
    17. Cast system is boon or bane ?
    18. What’s the difference in the modus operandi of Amir Khan’s “Satyameva jayate” and Anna Hazares movement?
    19. What will u do on your part to remove corruption? If you travel in a train without confirmed ticket will u bribe the TT for a seat?
    20. What do u mean by optimistic. Is it always good to be optimistic or it helps sometimes to be pessimist?
    21. What is difference between confidence and over confidence?
    22. What is the difference between hard work and smart work?
    23. What are your goals?
    24. What motivates you to do a good job?
    25. What makes you angry?
    26. Give an example of your creativity
    27. Describe ideal company, job, and location?
    28. What are your hobbies?
    29. Inspiration in your life and why?
    30. What was the toughest decision you ever had to make?
    31. Define success? and how do you measure up to your definition
    32. About present job (if employed)
    33. Why did you resign from your previous job?
    34. Why have you been unemployed so long?
    35. What was the toughest challenge you have ever faced?
    36. What would you say to your boss if he is crazy about an idea, but you think it stinks?
    37. Why should I hire you?
    38. Explain how you would be an asset to this organisation.
    39. If we give you a job will you leave IIT B or your organisation?
    40. What changes would you make if you came on board?

    Thanks
    Akshay.

  2. This was asked to me in one of my interview. Assuming Interviewer as I and me, the candidate as C.

    I: What's your strongest and weakest suit in mechanical, your topic of interest.

    C: Thermal sir except RAC is my strong point while material science bugs me

    I: Okay Shubham, then tell what if I heat a steel pole at 100 °C

    C: Heat transfer phenomenon sir, Fourier's law,Conduction.

    I: What if I increase temperature to 200 °C

    C: Conduction will increase sir.

    He kept increasing the temperature, and was still saying conduction. I was perplexed what he really wants to ask,as answering same thing was killing me.

    Finally when he said 1500 °C,

    C: The pole is going to melt.

    I: Hmm, are you sure?

    C: Yes sir, as melting point of steel is 1370 °C

    I: What if ask you to collect molten material and by using any suitable process make the pole again, will the new pole be same as prior one?

    Now this was tricky, my confidence sunk. It should be same, after all you are using the same material.

    "Properties of material change over recrystallization temperature"

    The most basic line of material science.

    He was smiling witty. He had sensed my horror. I already started respecting him to turn the question from my strong area to weak. Anyway gulping down I answered.

    C: No Sir, material properties will change so it will not be the same pole.

    His witty smile changed into a calm in one.

    Result: Selected

  3. Actually if you are in final year and preparing for GATE or other Competitive exam then you know that you must have good Basic Mechanical Knowledge. you must have clear ideas and concept related to mechanical stuffs like refrigeration, AC, Pump, etc. this will help you in Personal interview. But before PI you need to crack written test so  some basic mechanical questions must be refer. Here are some …

    1. What is the difference between scavenging and supercharging ?

    Ans: Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air.

    2. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes.Ans: Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively.

    3. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ?Ans: It will decrease.

    4. Why entropy change for a reversible adiabatic process is zero ?

    Ans: Because there is no heat transfer in this process.

    5. What are two essential conditions of perfect gas ?

    Ans: It satisfies equation of state and its specific heats are constant.

    6. Enthalpy and entropy are functions of one single parameter. Which is that ?

    Ans: Temperature.

    7. Why rate of condensation is higher on a polished surface compared to rusty surface ?

    Ans: Polished surface promotes drop wise condensation and does not wet the surface.

    more Mechanical Questions

  4. Here are some general technical questions that i would like to recommend you to solve or at least have an eye on those questions so that whenever in an interview someone asks you a question at that time you don't feel strange with those questions.

    If you want to have a set of 1000 technical questions for interview and along with that i will provide you a set of HR questions( if you want) also but for that you have to mail me at umang.pabari007@gmail.com any time or you can message me either on quora with your mail id or on facebook and here is my facebook account : Facebook

    Here is a list of 200 questions that i would like to share with you guys.

    1. What is the difference between scavenging and supercharging?
    2. What are the names given to constant temperature, constant pressure, constant volume , constant internal energy, constant enthalpy and constant entropy?
    3. In a Rankine Cycle, if max. steam pressure is increased keeping steam temp. and condenser pressure same , what will happen to dryness fraction of steam after expansion?
    4. Why entropy change for a reversible adiabatic process is zero?
    5. What are two essential conditions for perfect gas?
    6. Entahlpy and entropy are functions of one single parameter. Which is that?
    7. Why rate of condensation is higher on a polished surface than compared to rusty surface?
    8. How much resistance is offered to heat flow by drop wise condensation?
    9. What is the relationship between COP of heating and cooling?
    10. How much is the work done in Isochoric process?
    11. When max. discharge is obtained in nozzle?
    12. Under what condition work done in reciprocating compressor is least?
    13. What is the difference between stalling and surging in rotary compressor?
    14. Why the electric motor of a fan with backward curved blades is never got overloaded under any condition?
    15. Why the work per kg of air flow in axial flow compressor is less compared to centrifugal compressor for same ratio?
    16. What is the name given to portion of thermal energy to be necessarily rejected to environment?
    17. What is pitting ? How it is caused?
    18. What is caustic environment?
    19. Which impurities form Hard scale and which impurities form soft scale?
    20. What is the difference between hard water and soft water?
    21. Which two elements of feed water can cause corrosion of tubes and plates in boiler?
    22. What should be done to prevent a safety valve to stick to its seat?
    23. Why large boilers are water tube type?
    24. What type of boiler does not need a steam drum?
    25. Why manholes in vessels are usually elliptical in shape?
    26. Low water in boiler drum is unsafe because it may result in overheating of water tubes in furnace. Why it is unsafe to have high water in boiler drum?
    27. Why boiler is purged every time before starting firing of fuel?
    28. What is the principle of mechanical refrigeration?
    29. Why high latent heat of evaporation is desirable in a refrigerant?
    30. What is the critical temperature of a refrigerant?
    31. Maximum combustion temperature in gas turbines i of the order of 1100 to 10 degree Celsius whereas same is around 00 degree Celsius in IC engine? Why?
    32. Why efficiency of gas turbine is lower as compared to IC engines?
    33. What do you understand by timed cylinder lubrication?
    34. What is IIUCR in relation to petrol engine?
    35. In some engines glycerin is used in place of water for cooling. Why?
    36. Why consumption of lubricating oil is more in two-stroke cycle petrol engine than four stroke cycle petrol engine?
    37. As compression ratio increases , thermal n increases. How is thermal n is affected by rich and weak mixture?
    38. How engine design needs to be changed to burn lean mixture?
    39. Horse power of IC engines can be expressed as RAC rating , SAE rating or DIN rating. To which countries these standards belong?
    40. What is the use of flash chamber in a vapour compression refrigeration cycle to improve the COP of refrigeration cycle?
    41. Why pistons are usually dished at top?
    42. What is the function of thermostat in cooling system of an engine?
    43. What are the causes of failure of boiler tubes?
    44. What are the causes of failure for super heater tubes?
    45. Why super critical boilers use less amount of steel compared to non super critical boilers?
    46. Out of electric heater and Heat pump , which is economical in operation?
    47. Which furnace burns low-ash fusion coal and returns most of the coal ash in the slag?
    48. How the thickness of thermal boundary layer and thickness of hydrodynamic boundary layer related?
    49. What is the effect of friction on flow of steam through a nozzle?
    50. Why gas turbine power plant needs efficient compressor?
    51. Why rockets using liquid hydrogen have higher specific impulse compared to liquid hydrocarbon?
    52. Why axial flow compressor is preferred for gas turbines for aero planes?
    53. What is the effect of inter cooling in gas turbine?
    54. Why iso-octane is chosen as reference fuel foe S.I engines and allotted 100 value for its octane number?
    55. Why thermal efficiency of IC engine is more than the gas turbine plant?
    56. Which are the reference fuels for knock rating of SI engines?
    57. When effect of variations in specific heat is considered then how do maximum temperature and pressure vary compared to air standard cycle?
    58. Quantities like pressure, temperature , density , viscosity etc. are independent of mass. What are these called?
    59. The amount of radiation emitted per scm per sec is called..?
    60.  In convective heat transfer , if heat flux intensity is doubled hen temperature.
    61.  How you can define coal?
    62. Which pollutant is major greenhouse gas and what is its effect?
    63.  In order to increase efficiency and reduce CO emissions and other emissions , clear coal technologies are receiving major attention. What are these?
    64. What are the important operational performance parameters in design of fuel firing equipment?
    65. What is the difference between total moisture and inherent moisture in coal?
    66. Promixity analysis of coal provides data for a first, general assessment of a coal's quality and type. What elements it reports?
    67. Ultimate analysis of coal is elementary analysis. What it is concerned with?
    68. Explain the difference between AFBC , BFBC , PFBC and PCBC in regard to fluidised technologies.
    69. What is Schmidt plot for is used in heat transfer problems?
    70  In which reactor the coolant and moderator are the same?
    71. Which reactor has no moderator?
    72. What are the thermal neutrons?
    73. What is big advantage of fast breeder reactor?
    74. What is the purpose of biological shield in nuclear plants?
    75. Which two elements have same percentage in proximate and ultimate analysis of coal?
    76. On which analysis is based the Dulong's formula for the heating value of fuel?
    77. Which element causes difference in higher and lower heating values of fuel?
    78. Which heating value is indicated by a calorimeter and why?
    79. State the difference between ultimate and proximate analysis of coal?
    80. What is the fuel ratio?
    81. How the analyses and calorific values can be reported?
    82. What is the difference between nuclear fission and fission chain reaction.
    83. Expalin difference between fissile and fertile material.
    84. What do you understand by fuel cycle in nuclear plants?
    85. What is heavy water and what is its use in nuclear plants?
    86. What is a convertor reactor?
    87. Explain nuclear reactor in brief.
    88. What is the difference between conversion and enrichment.
    89. Disposal of radioactive waste materials and spent fuel is a major and important technology. How the waste radioactive material is disposed off?
    90. Which nuclear reactor uses water as a coolant, moderator and reflector?
    91. Which reactor produces more fissionable material than it consumes?
    92. Which reactor uses natural uranium as fuel?
    93. Which reactor uses heavy water as moderator?
    94. Which reactor requires no moderator?
    95. Which reactor uses primary coolant as fluoride salts of lithium , beryllium , thorium and uranium?
    96. Why an increase in area is required to produce an increase of velocity in case of supersonic flow?
    97. Under what circumstances would there be an increase in pressure in a divergent nozzle?
    98. Why water can't be used as refrigerant for small refrigerating plant?
    99. Which parameter remains constant in a throttling process?
    100 .What is the difference between isentropic process and throttling process?
    101. What is the difference between isotropic and anisotropic material?
    102. What are orthotropic materials?
    103. What is view factor?
    104. What properties need to be considered for applications calling for following requirements
      1.Rigidity
      2.Strength for no plastic deformation under static load
      3.Strength to withstand overload with fracture
      4.Wear resistance
    105. Explain the effects of alloying chromium and nickel in stainless steel.
    106. Mention two types of dislocations.
    107. What are the principle constituents of brass?
    108. What is curie print?
    109. Specific strength of material is very high when they are in fiber size but lower when they are in bar from why?
    110. What is the percentage of carbon in cast iron?
    111. Which element is added in steel to increase resistance to corrosion?
    112. Whether individual components in composite materials retain their characteristics or not?
    113. An elastomer is a polymer when its percentage elongation rate is?
    114. If percentage elongation of a material is more than 200% , it is classed as?
    115. Why is it that the max. value which the  residual stress can reach is the elastic limit of the material?
    116. Why fatigue strength decreases as size of a part increases beyond around 10 mm?
    117. Distinguish between creep and fatigue.
    118. While normal carburizing and nitriding surface treatments increase fatigue strength ,  excessive treatment may decrease the fatigue strength. Why?
    119. List at least two factors that promote transition from ductile to brittle fracture.
    120. Which theories of failure are used for a ductile materials and brittle materials?
    121. What does thermal diffusivity of metal signify.
    122. For conduction of heat, the instantaneous rate of heat flow is product of three factors, what are these?
    123. How convective heat transfer is affected and on what factors it depends?
    124. Which is the common element between brass and bronze?
    125. What does following alloy designation indicate FG 250?
    126. How is ceramic defined?
    127. Give one example of metal classified as per structure as BCC , FCC , HCP and CCP.
    128. What is the name of solid solution of carbon in alpha iron and delta iron?
    129. Explain the difference between pearlite and cementite
    130. Give one example each of the following proportion of materials dimensional , physical , technological and mechanical.
    131. For which parts the Wahl factor and Lewis form factor used?
    132. How oxygen can be removed from steel during melting? What are fully killed steels?
    133. Hydrogen cannot be removed easily from molten steel. What harm hydrogen has on property of steel?
    134. What is allotropic? In what forms of cubic pattern , iron exists?
    135. What is the difference between alpha , delta and gamma iron?
    136. Metals , in general are of low strength and do not possess required physio-chemical and technological properties for a definite purpose. Alloys are therefore more than metals alone. Discuss the arrangement of atoms and structures of alloys.
    137. What is the difference between isotropic and homogeneous material.
    138. Explain the difference between the points of inflexion and contra flexure.
    139. What is the difference between proof resilience and modulus of resilience?
    140. What is the difference between column and strut?
    141. Explain the difference between ferrite , austenite and graphite?
    142. Explain the terms solid solution , eutectic , eutectoid and peritectic.
    143. What do you understand by critical points in iron carbon diagram?
    144. Why PERT is preferred over CPM for evaluation of project?
    145. What is percentage of chromium in 18:4:1 IISS?
    146. What is stellite?
    147. Which rays are produced by cobalt-60 in industrial radiography?
    148. What are killed steels and what for these are used?
    149. What is critical temperature in metals?
    150. Car types are usually made of?
    151. What is the structure of pure iron and whether it is soft or hard?
    152. Which elements increase the corrosion resistance of steel?
    153. What causes hardness in steel? How heat treatment alters properties of steel?
    154. Explain the formation of microstructures of pearlite , bainite and martensite in steel.
    155. How with alloying of steel it is possible to a achieve properties which cannot be achieved with heat treatment?
    156. What are the major effects of alloying elements?
    157. What is the difference between austenite stabilisers and ferrite stabilisers?
    158. What are the effects of carbon on the properties of steel?
    159. What is the role of silicon as alloying element in steels?
    160. Discuss the role of manganese in alloying steels.
    161. Define buckling factor.
    162. What do you understand by catenary cable?
    163. What is coaxing?
    164. What is difference between conjugate beam and continuous beam?
    165. What is isentropic material?
    166. Explain difference between modulus of resilience and modulus of rigidity?
    167. What is the difference between basic hole and basic shaft?
    168. What for pyranometer is used?
    169. Describe transfer machines in brief.
    170. What is burnt-out point?
    171. What do you understand by eutectic?
    172. Explain the difference between grey iron and white iron. What is mottled iron?
    173. The graphite in grey irons exists in the form of flakes which act as stress-raisers under tensile loading and consequently grey irons have relatively low tensile strength and ductility. Still grey iron is extensively used in engineering. Why?
    174. Under what condition a convergent divergent nozzle required?
    175. What is endurance limit and what is its value for steel?
    176. How the net work to drive a compressor and its volumetric efficiency behave with increase in clearance volume?
    177. What do you understand by sulphur print?
    178. What is the effect of addition of zinc in copper? What is the use of 70/30 brass?
    179. What is the difference between brass and bronze?
    180. What for admirality brass used?
    181. What is the maximum use of magnesium?
    182. What for zinc finds application?
    183. Which factors influence the type of fracture in failure of a material?
    184. What is the name given to the ratio of actual cycle efficiency and ideal cycle efficiency.
    185. List two effects of manganese in plain carbon steels.
    186. In which process internal energy remains constant?
    187. What is VSD?
    188. What is temper embrittlement in alloy steels and what are its effects?
    189. What are whiskers?
    190. What is Bauschinger effect?
    191. What is the difference between heat capacity and specific heat of a material?
    192. Explain the rule to find specific heat of aqueous solutions.
    193. What do you understand by latent heat ? Give four examples of latent heats.
    194. Define the terms free energy and free enthalpy. What is their significance and importance?
    195. Whether the superheated steam can be treated like ideal gas?
    196. Out of constant pressure and constant volume lines on TS diagram which line has higher slope? And whether slope is constant or variable?
    197. Whether entropy is intensive property or extensive property?
    198. In which process fluid expands but does no work?
    199. What is Hess law?
    200. What is the purpose of scrapper ring?
     
    All the best.

    Thanks,
    Umang Pabari.

  5. Each and every interview starts with question from the chairman of interview. He normally asks candidate to say few words about family and education background. Normally he asks, or start the interview by asking, 'Tell me about yourself'. Candidate should reply to this question by giving just brief overview of name, education background, family and family background.

    1.  What are you doing nowadays?
    Ans :

    • They are looking for your mental attitude by asking you this question.
    • If you are finding job, you should straight forward tell them the truth. They will ask for the reason why there is delay in getting job? You should tell the correct reason behind it. They actually find whether candidate is  right person with right attitude or not. Do not give meaningless answer. They will find the pit hole in it and mark them as negative points.
    • If you are working somewhere else, tell the complete details, do not hide anything. They will further ask you about company and designation of yours and some question related to it measure your behavior in that company or professional life.

    2. What is your favorite subject in Mechanical engineering?

    Ans:   

    • Just be prepared for this question. This is the moment where you can prove yourself as sound in knowledge by saying your favorite subject. Normally they are looking for the subject in which their company is based on. If you are applying for the design job and you tell them thermal science as favorite subject, there is no problem. They will just check whether you are speaking truth or not. Do not tell them your favorite subject is Machine Design. If they keep throwing question regarding Machine Design, you will be caught. Do not worry if you tell other than the subject of company. Be true to yourself. You will be trained once you will be recruited.

    3. What was your project topic during Mechanical engineering?

    Ans:

    • They will looking for leadership and overall quality in this question. If you did project in group work, they will find out your leadership quality by related question.
    • What was your role?
    • How much time it has taken to complete the project?
    • What is the role of guide in the project? Thus they will measure you

    4. How do you see yourself after 5 years from now?

    Ans :

    • They want leaning and growth as your aim in this question. Do not tell I want to be General Manager or higher post in short time. Itis joke actually. Tell the systematic plan for pursuance of your goal.

    5. What are the software you know?

    Ans :

    • You should have basic software knowledge to be used in mechanical engineering work. You should know AutoCAD, Pro-Engineer and one Analysis software like ANSYS.

    For more technical interview questions & answers for Meachanical Engineering follow my blog at

    Mechanical Engineering Interview Questions & Answer

  6. It was namesake actually.

    The company was Gherzi eastern.
    My general aptitude and technical aptitude test went very well and I was shortlisted for the next round, which was a group discussion.
    I performed well in that too as these things weren't really daunting for me.
    Based on my performance I was the only person shortlisted from Mechanical branch though having lesser grades than many. One was shortlisted from electrical and 5 from civil. It was no surprise as the company is all about construction projects.
    The civil students appeared for the interview in the college itself. Each interview lasted for about half an hour and all of them got selected too.

    The remaining 2 were called to their head office in Santacruz for their PI.
    Maybe because the guy who came to interview was himself a civil guy.

    I was all excited and nervous. So next day I was there first thing in the morning. Clean shaven, hair trimmed and with a new disproportionate tie.

    I was asked to fill a form and to wait for over 2 hours.

    When I was called by the man for the interview I observed that he wasn't really that important a man. I mean he didn't even have his own cabin.

    So, anyways, he started asking questions about where I live and what was my final year project about. I remember him asking only these 2 questions and maybe one about me being Sindhi.

    When I was done answering he started saying things that didn't make sense. He was all about why I was not fit for the job and all.
    WTF!!!
    He decided that without asking me any technical questions.

    As I remember correctly, the electrical guy's interview lasted for 10 mins. Mine didn't even last for 5 mins.

    I was all worked up. What's the point of allowing other branches to attempt if you only want civil people?
    Why give false hopes?

    On the way back when my head got a bit cooler, I understood the dynamics.

    They wanted only civil guys but they also didn't want to spoil their relation with the college as it was the best in Mumbai. SPCE it is.
    So, for the namesake they had this process of pretentious interviews.

    That day I decided, I won't ever go for a company job interview again. And I didn't. Now I am a teacher in Mechanical branch and I am doing well.

  7. Well the questions asked in Mechanical Engineering interview depends upon the industry or field in which you are applying . If you are applying for job interview for say TATA MOTORS or any  automotive industry than   be prepared for questions specifically in the field of IC engines  ,Thermodynamics,Production process etc that are employed in Automobile production. So your preparation should be according to the company profile in which you are applying so be focussed specifically on this and  try to bring the interviewer to your strong areas so that he can see your real hold on the subject, knowledge and problem tackling abilities in that field.
    Some questions generally asked for fresher  recruitment of Mechanical Engineers  in automobile  companies are
    1. distinguish between SI and CI engines.What are ranges of compression ratios in both of them.
    2.what is knocking in engines.how would you control it in both SI and CI.
    3. how to control emissions in both SI and CI engines.
    4.draw and explain 4 stoke petrol and diesel engines.
    5.how transmission system in cars work.
    6.what are catalytic converters
    7. what are some green fuels for automobiles.
    8.give an example of heat exchanger within the car and describe the heat transfer process in it.
    9.describe the production processes employed in manufacturing of automobile .
    10.which heat treatment processes should the various components of Automobile should undergo and also explain the principle of processes.
    11.what is a car differential.
    12. describe the manufacturing processes used to manufacture gears.
    13.describe welding and how it can be automated in car industry.
    14. what is blow molding process where it is used.
    15.what is bhp.
    16. explain the function of carburettor system in automobile why it is needed and how it can be maintained .
    17. what is production planning.

    Apart from these just focus on your textbook and try to hold a grasp on the basics if you are fresher no need to panic the interviewer will just ask simple questions based on your Mechanical Engineering course and if you are a professional than show your skills and experience to the interviewer.
    (source : from my own  personal interviews )

    Edit: Some guys are asking me  for the detailed answers of the above questions well I can do that but that is not going to help you in any way because these are just sample questions that I have faced in various interviews during my campus placement drive and I have compiled these into a list but when you guys will face your respective interviews the questions that will be asked depends a lot on the interviewer panel so I would advice instead of asking for answers you should improve your basics in core mechanical engineering subjects.

    For IC engine follow the book by V Ganesan IC Engines it is a compact but still a great book and it will help you to  master the IC Engine subject.

  8. This one happened while I was still in college. In L&T I was asked a lot of technical questions, about manufacturing processes. One of the question was 'Where is gas welding typically used?' I dint answer the question. So I remember it. I dont remember anyother technical questions from that day. But then  the interviewer had a  change of heart and started testing my general knowledge. It went something like this.

    Interviewer: Do you read newspapers?
    Me: No. I watch TV news once in a while. I am not too interested in NEWS! (never make this statement to a man who is above 30, I now follow most current events, but I still dont read the newspaper)
    I: So tell me about the 2G scam.
    Mind Voice: Why are you asking me things I just told that I am not interested in.
    M: There was something wrong in the way spectrum was allocated!
    I: Hmmm, who is responsible for this?
    M: T R Balu.
    I: NO IT IS RAJA!!!
    M: I am sorry, I got confused between the two current DMK ministers at the centre.
    Interviewer gives me a long hard look.
    I: Have you been to Mumbai?
    M: No.
    I: Do you know where Gate way of India is?
    M: Mumbai!
    I: Where in Mumbai?
    M: Near the beach?
    I: Do you know the places in mumbai where the terrorists attacked?
    M: Taj hotel, ..
    I: And Taj hotel faces the gateway of India.
    M: Oh ok.
    Interviewer sighs! I start feeling that this is not going in favour of me.
    I: Who is A Premji?
    Mind Voice: Thank god!
    M: Premji Amaran is a Tamil actor and has acted in Chennai 600008, Saroja ….
    I: ASIM PREMJI IS THE CHAIRMAN OF WIPRO!
    M: ………..
    I: The interview is over, you may go.
    M: Thank You.

    That is the only interview which was not succesful of the four ones I have attended so far! (Thank God!), and thats why I wrote this down.

    Needless to say I was not selected. This is an example of how not to perform in an interview.

  9. Presume you are fresher. Generally following questions will be asked.

    1. What is your special subject
    2. What was your project. Explain
    3. What are your interests
    4. What is your career objective
    5. Why you want to join our company
    6. What department you would like. Design, project, purchase. Why

    What would be judged is your self confidence, smartness, politeness, guestures, communication skills, ability to discuss, appearance, general likings etc
    If you are experienced then mainly questions will revolve round work done by you and your interests.

  10. Hi,

    I would like to share an experience of my friend in BARC interview. He is mechanical engineer too. He got selected in BARC and then he started to prepare for interview, BARC conduct one of the toughest technical interview. He was little bit nervous cause he heard about many incidence about BARC interview. After some questionings, he was unable to answer some questions, then he got worried and more nervous.

    They were firing questions back to back.He just wanted to leave but he couldn't. After that interviewer asked a simple question that my friend fortunately knew, they offered pen and paper to write answer. My friend was writing suddenly interviewer said STATUE , Now draw Bending moment diagram of this pen paper system. My friend was like "what the heck" .. Ha ha ha

    Another incident was, They offered tea and biscuit , fellow was relaxed he took tea and biscuit. My fellow was a failure at dipping biscuit in tea, dipped part of biscuits fell down into cup. Suddenly interviewer asked, what kind of failure is this.. It was very good experience for my fellow 🙂

  11. Each and Every interview  comes with four standard areas, whether its structured interviews or unstructured interview .

    Here are those four areas :

    1. General Areas e.g. Tell me about yourself
    2. Past Experience Areas e.g. What you have done in past
    3. Technical Area e.g. Core areas of your expertise and study
    4. Misc e.g Puzzles, presence of mind, Written test, problem solving

    Here is one example of General Areas Qs.

  12. Thanks for the A2A.

    I would like to highlight some general points about mechanical interviews. You can enter the interview stage only if you have passed the written test (Technical and aptitude). All interviews will always start with "Tell me about yourself". Then they will shift to your resume and if they are interested in any of your doings you will be questioned on that. So be careful on resume preparation and include only things that you have done and have good knowledge in it.

    Next, based on the title and role of the job, the interview varies. They will test you on the areas where you will be put to work if you are selected. So vary your resume according to the company profile (For example: Areas of interest).

    If you have convinced the interviewer till now. Then you will be checked whether mentally you are ready for the job and whether you can work in a team. They also see whether you are looking for a long term commitment. If you say that you will be going for higher studies in an year, you will surely be rejected.

    This is the general process and in some interviews the technical and HR  rounds will be separated. But the procedure is same as said earlier.

    To put it in a nut shell:

    1) Prepare your resume properly. Be thorough in all the things you have specified.

    2) Show your skills and willingness to take up the job is selected.

    3) Be yourself.

    4)Admit if you are not sure of something. Don't try to manage.

    All the best




    EDIT 1:
    I would like to add few more things.

    1) Make yourself thorough with the first 2 or 3 chapters in basic Mechanical books. By that i mean,

    Kinematics – R.S.Khurmi
    Dynamics  – R.S.Khurmi
    Thermodynamics – Rajput
    Fluid Mechanics – Bansal, Rajput or Khurmi​
    Engineering Graphics – K.V.Natrajan
    Strength of materials- R.S.Khurmi
    Manufacturing Technology – VJ Ragavan 😉

    These are the few books i referred and the choice is yours but make yourself thorough in first 3 chapters of these subjects. Because all the basics for that subject wil be discussed in those and mostly you will be questioned in that during an interview. 90% Success is assured.

    2) Then choose one or two subjects from the above and study it top to bottom. This makes your area of interest.

    3) Very rarely you will be asked some tricky questions and if that happens use your brain if its beyond your knowledge. They will be testing your presence of mind sometimes.

    I will keep editing if anything strikes me.

  13. Here some Mechanical engineering Interview Questions given below

    1. Explain the second law of thermodynamics.
    2. What is ferrite?
    3. What is a cotter joint?
    4. Explain Otto cycle.
    5. What are the differences between pneumatics and hydraulics?
    6. What is a positive displacement pump?
    7. What are the advantages of gear drive?
    8. Which conducts heat faster steel copper or brass?
    9. What is an orthographic drawing?
    10. What does angular momentum mean?

    It is not enough to have solid answers only for the above questions. You need to be prepared for the full spectrum of questions that may be presented. For further practice, make sure you go through the required mock interview in online. I would like to suggest InterviewBuddy-https://interviewbuddy.in/ is the best website to practice and prepare the interview with experts in real-time.

  14. Learn and practice Technical Interview Prep, Interview Preparation, Mechanical Interview Questions and answers with explanation for interview, placement test, online test, competitive examination and entrance test
     
    1. Explain the second law of thermodynamics.
    The entropy of the universe increases over time and moves towards a maximum value.
     
    2. What kinds of pipes are used for steam lines?
    Normally galvanized pipes are not used for steam. Mild steel with screwed or welded fittings are the norm. Pressure and temperature are very important factors to be considered in what type of materials to be used. Steam even at low pressures can be extremely dangerous.
     
    3. What is the difference between shear centers flexural center of twist and elastic center?
    The shear center is the centroid of a cross-section. The flexural center is the center of twist, which is the point on a beam that you can add a load without torsion. The elastic center is located at the center of gravity. If the object is homogeneous and symmetrical in both directions of the cross-section then they are all equivalent.
     
    4. What is ferrite?
    Magnetic iron rock
     
    5. What is the difference between projectile motion and a rocket motion?
    A projectile has no motor/rocket on it, so all of its momentum is given to it as it is launched. An example of a projectile would be pen that you throw across a room. A rocket or missile does have a motor/rocket on it so it can accelerate itself while moving and so resist other forces such as gravity.
     
    6. What is a cotter joint?
    These types of joints are used to connect two rods, which are under compressive or tensile stress. The ends of the rods are in the manner of a socket and shaft that fit together and the cotter is driven into a slot that is common to both pieces drawing them tightly together. The tensile strength of the steel is proportionate to the strength needed to offset the stress on the material divided by the number of joints employed.
     
    7. What is the alloy of tin and lead?
    A tin and lead alloy is commonly called solder. Usually solder is a wire with a rosin core used for soldering. The rosin core acts as a flux.
     
    8. What does F.O.F. stand for in piping design?
    FOF stands for Face of Flange. A flange has either of the two types of faces:
    a) Raised face
    b) Flat face
    The F.O.F is used to know the accurate dimension of the flange in order to avoid the minute errors in measurement in case of vertical or horizontal pipelines.
     
    9. Explain Otto cycle.
    Otto cycle can be explained by a pressure volume relationship diagram. It shows the functioning cycle of a four stroke engine. The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, starting of combustion, power stroke, heat exchange stroke where heat is rejected and the exhaust stroke. It was designed by Nicolas Otto, a German engineer.
     
    10. What is gear ratio?
    It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

    11. What is annealing?
    It is a process of heating a material above the re- crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.
     
    12. What is ductile-brittle transition temperature?
    It is the temperature below which the tendency of a material to fracture increases rather than forming. Below this temperature the material loses its ductility. It is also called Nil Ductility Temperature.
     
    13. What is a uniformly distributed load?
    A UDL or uniformly distributed load is a load, which is spread over a beam in such a way that each unit length is loaded to the same extent.
     
    14. What are the differences between pneumatics and hydraulics?
    a) Working fluid: Pneumatics use air, Hydraulics use Oil
    b) Power: Pneumatic power less than hydraulic power
    c) Size: P components are smaller than H components
    d) Leakage: Leaks in hydraulics cause fluid to be sticking around the components. In pneumatics, air is leaked into the atmosphere.
    e) Pneumatics obtain power from an air compressor while hydraulics require a pump
    f) Air is compressible, hydraulic oil is not
     
    15. What is enthalpy?
    Enthalpy is the heat content of a chemical system.
     
    16. What is a positive displacement pump?
    A positive displacement pump causes a liquid or gas to move by trapping a fixed amount of fluid or gas and then forcing (displacing) that trapped volume into the discharge pipe. Positive displacement pumps can be further classified as either rotary-type (for example the rotary vane) or lobe pumps similar to oil pumps used in car engines. These pumps give a non-pulsating output or displacement unlike the reciprocating pumps. Hence, they are called positive displacement pumps.
     
    17. Why would you use hydraulics rather than pneumatics?
    Hydraulics is suitable for higher forces & precise motion than pneumatics. This is because hydraulic systems generally run at significantly higher pressures than pneumatics systems. Movements are more precise (repeatable) because hydraulics uses an incompressible liquid to transfer power whilst pneumatics uses gases. Pneumatic systems have some advantages too. They are usually significantly cheaper than hydraulic systems, can move faster (gas much less viscous than oil) and do not leak oil if they develop a leak.
     
    18. What is isometric drawing?
    It is a 3-D drawing used by draftsmen, architects etc
     
    19. What are the advantages of gear drive?
    In general, gear drive is useful for power transmission between two shafts, which are near to each other (at most at 1m distance). In addition, it has maximum efficiency while transmitting power. It is durable compare to other such as belts chain drives etc. You can change the power to speed ratio.
    Advantages: –
    It is used to get various speeds in different load conditions.
    It increases fuel efficiency.
    Increases engine efficiency.
    Need less power input when operated manually.
     
    20. Which conducts heat faster steel copper or brass?
    Copper conducts heat faster than steel or brass. Any material that is good for conducting heat is also good for electricity in most cases. Wood terrible for transferring heat thus is also insulator for electric.
     
    21. How pipe flanges are electrically insulated?
    Pipe flanges are protected from corrosion by means of electrolysis, with dielectric flanges. The piping system is electrically insulated by what is called a sacrificial anode. A bag of readily corrodible metal is buried in the ground with a wire running from the pipe to the bag so that the sacrificial anode will corrode first. If any electrical current charges the pipe, it also serves as a ground.
     
    22. What is a Process Flow Diagram?
    A Process Flow Diagram (or System Flow Diagram) shows the relationships between the major components in the system. It also has basic information concerning the material balance for the process.
     
    23. Where pneumatic system is used?
    Any system needs redundancy in work needs pneumatics, because the compressor of the pneumatic system has periodical operations (intermittent work, not as hydraulic pump). The compressed air could be accumulated in tanks with high pressures and used even if the compressor failed.
     
    24. Why gas containers are mostly cylindrical in shape?
    The most efficient shape for withstanding high pressure is a sphere but that would be costly to manufacture. A cylinder with a domed top and a domed bottom (look underneath, the flat base is actually welded around the outside, the bottom of the gas container is actually domed) is a much cheaper shape to manufacture whilst still having good strength to resist the internal gas pressure.
     
    25. How is marten site structure formed in steel?
    Marten site transformation begins when austenite is cooled below a certain critical temperature, called the martensitic start temperature. As we go below the marten site start temperature, more and more marten site forms and complete transformation occurs only at a temperature called marten sire finish temperature. Formation of marten site requires that the austenite phase must be cooled rapidly.
     
    26. What is an orthographic drawing?
    Orthographic projections are views of a 3D object, showing 3 faces of it. The 3 drawings are aligned so that if the page were folded, it would create part of the shape. It is also called multiview projections. The 3 faces of an object consist of its plan view, front view and side view. There are 2 types of orthographic projection, which are 1st angle projection and 3rd angle projection.
     
    27. What is representative elementary volume?
    Smallest volume over which measurements can be made that will yield a representative of the whole.
     
    28. Why are LNG pipes curved?
    LNG pipes are curved because LNG is condensed gas (-164 ℃) so it can expand the pipes that is what engineers designed the LNG pipes are curve type.
     
    29. What does angular momentum mean?
    Angular momentum is an expression of an objects mass and rotational speed. Momentum is the velocity of an object times it is mass, or how fast something is moving how much it weigh. Therefore, angular momentum is the objects mass times the angular velocity where angular velocity is how fast something is rotating expressed in terms like revolutions per minute or radians per second or degrees per second.
     
    30. Can you use motor oil in a hydraulic system?
    Hydraulic fluid has to pass a different set of standards than motor oil. Motor oil has tackifiers, lower sulfur content, and other ingredients that could prove harmful to the seals and other components in a hydraulic system. If it is an emergency only should you do it.
     
    31. What causes white smoke in two stroke locomotive engines?
    That is the engine running too lean (lack of fuel). This condition will lead to overheating and failure of the engine.
     
    32. What is the role of nitrogen in welding?
    Nitrogen is used to prevent porosity in the welding member by preventing oxygen and air from entering the molten metal during the welding process. Other gases are also used for this purpose such as Argon, Helium, Carbon Dioxide, and the gases given off when the flux burns away during SMAW (stick) welding.
     
    33. What does Green field project mean?
    Green field projects are those projects, which do not create any environmental nuisance (pollution), follows environmental management system and EIA (environment impact assessment). These projects are usually of big magnitude.
     
    34. Is it the stress that, produces strain or strain produces stress?
    A Force applied to an object will cause a displacement. Strain is effectively a measure of this displacement (change in length divided by original length). Stress is the Force applied divided by the area it is applied. (E.g. pounds per square inch) Therefore, to answer the question, the applied force produces both “Stress and Strain”. “Stress and Strain” are linked together by various material properties such as Poisson's ratio and Young's Modulus.
     
    35. How does iron ore turn into steel?
    To make Steel, Iron Ore is refined into iron and all the carbon is burned away using very high heat (Bessemer). A percentage of Carbon (and other trace elements) are added back to make steel.
     
    36. What is knurling?
    Knurling is a machining process normally carried our on a centre lathe. The act of Knurling creates a raised criss- cross pattern on a smooth round bar that could be used as a handle or something that requires extra grip.
     
    37. What is the mechanical advantage of a double pulley?
    It only takes half the effort to move an object but twice the distance.
     
    38. What is extruding aluminum?
    Extrusion is the process where a metal or a metal bar is pulled through a mandrel to elongate it and/or give it a final shape. Extruded Aluminum is a common form of making small aluminum wire, bars or beams and many varieties of small non-structural, decorative pieces.
     
    39. What is a Newtonian fluid?
    A Newtonian fluid possesses a linear stress strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.
     
    40. What are the points in the stress strain curve for steel?
    Proportional limit, elastic limit or yield point, ultimate stress and stress at failure

  15. Generally asked question in an interview are following

    1. Which subject do you like
    2. What were you project
    3. Why do you want to join our company
    4. What do you know about our company
    5. What's your career object
    6. In which department would you like to work

    But other questions varies from interview to interview like i have appeared in Nuclear Power Corporation India Limited and the 1st question was just write your three favourite subject so I wrote SOM, MD & Thermo then they told me to drive expression for thin pressure vessel but when I appeared for IES interview that time they also asked me about my favourite subject and my answer was same but after that they asked me about black box so it depends on the mood of interviewer at some extent we be can get the idea that what they will ask in interview but it doesn't work always.

  16. These were some of the questions I came across during my technical interviews which I find tricky:

    1.Difference between Pipe and tube?

    Answer:

    • There always a debate between differentiation of pipe and tube. Pipe is always designated by its Inside Diameter (ID) because main purpose of pipe is to carry fluid, while the
    • Tube is always designated by its Outside Diameter (OD). Pipe's thickness is sometimes called asschedule and tube's thickness isgauge.
    • As per the tolerance basis, tubes requires lower tolerances as to that of pipe and tubes are more costlier in manufacturing compared to pipe production.

    2. Draw a possible isometric view for the object that has the following plan and elevation views?

    Answer:

    3.Difference between Performance and Efficiency?

    Answer:

    The accomplishment of a given task measured against preset known standards of accuracy, completeness, cost, and speed is called as Performance. Efficiency is defined as the input given and the work obtained from that input like money, time, labour etc. It’s the main factor of productivity.

    Hope it's helpful.

    Edit: Tubes require lower tolerances.

  17. # Top 200 mostly asked question in Interview of Mechanical Engineer

    MECHANICAL ENGINEERING Interview Questions with Answers :-

    1. What is the difference between isotropic and anisotropic materials ?

    If a material exhibits same mechanical properties regardless of loading direction, it is isotropic, e.g., homogeneous cast materials. Materials lacking this property are anisotropic.

    2. What are orthotropic materials?

    It is a special class of anisotropic materials which can be described by giving their properties in three perpendicular directions e.g. wood; composites.

    3. What is view factor ?

    View factor is dependent upon geometry of the two surfaces exchanging radiation.

    4. What properties need to be considered for applications calling for following requirements :

    (i) rigidity

    (ii) strength for no plastic deformation under static load

    (iii) strength to withstand overload without fracture.

    (iv) wear resistance

    (v) reliability and safety.

    (i) Rigidity—Elastic modulus and yield strength

    (ii) Strength (for no plastic deformation under static loading)—yield point

    (iii) Strength (overload)—Toughness and impact resistance

    (iv) Wear resistance—Hardness

    (v) Reliability and safety—Endurance limit and yield point.

    5. Explain the effects of alloying chromium and nickel in stainless steel.

    Addition of nickel and chromium increases the tensile strength and increase in resistance to corrosion takes place.

    MECHANICAL ENGINEERING Interview Questions

    6. Mention two types of dislocations.

    Dislocation refers to a break in the continuity of the lattice. In edge dislocation, one plane of atoms gets squeezed out. In screw dislocation the lattice atoms move fom their regular ideal positions.

    7. What are the principal constituents of brass?

    Principal constituents of brass are copper and zinc.

    8. What is Curie point ?

    Curie point is the temperature at which ferromagnetic materials can no longer be magnetised by outside forces.

    9. Specific strength of materials is very high when they are in fibre size but lower when they are in bar form Why ?

    Crystal structure has ordered, repeating arrangement of atoms. Fibres are liable to maintain this and thus have high specific strength. As size increases, the condition of ordered and repeating arrangements can’t be guaranteed because of several types of defects and dislocations and thus the specific strength gets lower.

    10. What is the percentage of carbon in cast iron ?

    2.5%.

    11. Which element is added in steel to increase resistance to corrosion ?

    Chromium.

    12. Whether individual components in composite materials retain their characteristics or not?

    yes.

    13. An elastomer is a polymer when its percentage elongation rate is ?

    Greater than 100%.

    14. If percentage elongation of a material is more than 200%, it is classed as ?

    Rubber.

    15. Why is it that the maximum value which the residual stress can reach is the elastic limit of the material ?

    A stress in excess of elastic limit, with no external force to oppose it, will relieve itself by plastic deformation until it reaches the value of the yield stress.

    16. Why fatigue strength decreases as size of a part increases beyond around 10 mm?

    Perfection of material conditions is possible at lower sizes and as size increases, it is not possible to attain uniform structure of the material.

    17. Distinguish between creep and fatigue.

    Creep is low and progressive deformation of a material with time under a constant stress at high temperature applications. Fatigue is the reduced tendency of material to offer resistance to applied stress under repeated or fluctuating loading condition.

    18. While normal carburising and nitriding surface treatments increase fatigue strength, excessive treatment may decrease the fatigue strength. Why ?

    .Normal carburising/nitriding treatments increase volume due to phase transformation at Surface and introduce residual compressive surface stress and thus increase the fatigue strength. By excessive treatment the high compressive stresses are introduced but these are balanced by high internal tensile stresses of equal value and the subsurface fatigue cracks may develop in the regions of high tensile stress and lead to early fatigue failure.

    19. List at least two factors that promote transition from ductile to brittle fracture.

    Manner of loading, and the rate of loading promote transition from ductile to brittle fracture. A machine member may have ductile failure under static loading but may fail in brittle fashion when the load is fluctuating. Similarly a material may evidence ductile failure under tensile loading at ordinary testing speed but if load is applied at a high velocity then failure may be brittle.

    20. Which theories of failure are used for (a) ductile materials, and (b) brittle materials ?

    For ductile materials, theories of failure used are maximum shear stress theory, and maximum energy of distortion theory; while for brittle materials, theory of maximum principal stress, and maximum strain are used.

    21. What does thermal diffusivity of metals signify.

    Thermal diffusivity is associated with the speed of propagation of heat into solids during changes in temperature with time.

    22. For conduction of heat, the instantaneous rate of heat flow is product of three factors. What are these ?

    Ans:

    1. Area of the section of the heat flow path, perpendicular to the direction of heat flow.
    2. temperature gradient, i.e. change of temperature w.r.t. length of path.
    3. Thermal conductivity of material.

    23. How convective heat transfer is effected and on what factors it depends ?

    Convective heat transfer is effected between a solid and fluid by a combination of molecular conduction within the fluid in combination with energy transport resulting from the motion of fluid particles. It depends on boundary layer configuration, fluid properties and temperature difference.

    24. Which is the common element between brass and bronze ?

    Copper.

    25. What does following alloy designation indicate FG 250 ?

    Grey cast iron with tensile strength of 250 MPa.

    26. How is ceramic defined ?

    It is a solid formed by combination of metallic and non-metallic elements.

    27. Give one example of metal classified as per structure as BCC, FCC, HCP and CCP.

    Ans:

    • BCC (body centred cubic) structure—Molybdenum
    • FCC (face centred cubic) structure—Aluminium
    • HCP (hexagonal closed packed) structure—Zinc
    • CCP (cubic dosed packed) structure-Copper.

    28. What is the name of solid solution of carbon in alpha iron and delta iron ?

    Ferrite and austenite respectively.

    29. Explain the difference between pearlite and cementile ?

    Pearlite is eutectoid mixture of ferrite and cementile. Cementite is chemical compound of iron and carbon.

    30. Give one example each of the following proportion of materials dimensional, physical, technological and mechanical.

    Roughness, enthalpy, toughness, and hardness respectively.

    31. For which parts the Wahl factor and Lewis form factor used ?

    For springs and gears respectively.

    32. How oxygen can be removed from steel during melting? What are fully killed steels ?

    Oxygen can be removed by adding elements such as manganese, silicon or aluminium which, because of their high affinity for oxygen, react with it to form non-metallic oxides which rise into the slag. Steels which have had most of their dissolved oxygen removed are called “fully killed steels”.

    33. Hydrogen cannot be removed easily from molten steel. What harm hydrogen has on property of steel ?

    Execessive hydrogen results in the formation of small fissures often described as hairline cracks or flakes in the steel. Large forgings in alloy steel are particularly sensitive to this phenomenon.

    34. What is allotrope ? In what forms of cubic pattern, iron exists ?

    Some elements exist in more than one crystalline form. Each form is known as “allotrope”. Iron exists in two forms of cubic pattern, namely body centered cubic (bcc) and face-centered cubic (fee).

    35. What is the difference between alpha iron, delta iron and gamma iron ?

    The bcc form of iron exists between room temperature and 910°C, and between 1400°C and the melting point at 1539°C. The lower temperature form is known as “alpha”-iron and the higher temperature form as “delta”-iron. The face-centered cubic form existing between 910°C and 1400°C is referred to as “gamma-iron”.

    36. Metals, in general are of low strength and do not possess required physio-chemical and technological properties for a definite purpose. Alloys are therefore more than metals alone. Discuss the arrangement of atoms and structures of alloys.

    Alloys are produced by melting or sintering two ore more metals, or metals and a non-metal, together. Alloys possess typical properties inherent in the metallic state. The chemical elements that make up an alloy are called its components. An alloy can consist of two or more components. The phase and structures of alloys describe the constitution, transformations and properties of metals and alloys. A combination of phases in a state of equilibrium is called a system. A phase is a homogeneous portion of a system having the same composition and the same state of aggregation throughout its volume, and separated from the other portions of the system by interfaces. For instance, a homogeneous pure metal or alloy is a single-phase system. A state in which a liquid alloy (or metal) coexists with its crystals is a two-phase system. Structure refers to the shape, size or the mutual arrangement of the corresponding phases in metals or alloys. The structural components of an alloy are its individual portions, each having a single structure with its characteristic features.

    37. What is the difference between isotropic material and homogeneous material ?

    In homogeneous material the composition is same throughout and in isotropic material the elastic constants are same in all directions.

    38. Explain the difference between the points of inflexion and contraflexure.

    At points of inflexion in a loaded beam the bending moment is zero and at points of contraflexure in loaded beam the bending moment changes sign from increasing to decreasing.

    39. What is the difference between proof resilience and modulus of resilience ?

    Proof resilience is the maximum strain energy that can be stored in a material without permanent deformation. Modulus of resilience is the maximum strain energy stored in a material per unit volume.

    40. What is the difference between column and strut ?

    Both column and strut carry compressive load. Column is always vertical but strut as member of structure could carry axial compressive load in any direction.

    41. Explain the difference between ferrite, austenite and graphite ?

    Ferrite is the solid solution of carbon and other constituents in alpha-iron. It is soft, ductile and relatively weak.

    Austenite is the solid solution of carbon and other constituents in gamma-iron. It exists in ordinary steels at elevated temperatures, but it is also found at ordinary temperatures in some stainless steels.

    Graphite has a hexagonal layer lattice. ‘

    42. Explain the terms solid solution, eutectic, eutectoid and peritectic.

    Ans:

    • Solid Solution. When a homogeneous mixture of two (or more) atomic forms exists in solid state, it is known as solid solution.
    • Eutectic. A mixture of two (or more) phases which solidify simultaneously from the liquid alloy is called an eutectic. Alloys in which the components solidify simultaneously at a constant temperature the lowest for the given system, are called eutectic alloys.
    • Eutectoid. Eutectoid alloys are the alloys for which two solid phases which are completely soluble become completely insoluble on cooling before a certain temperature called eutectoid temperature.
    • Peritectic. A peritectic transformation involves a reaction between a solid and liquid that form a different and new solid phase. This three phase transformation occurs at a point called peritectic point.

    43. What do you understand by critical points in iron, iron-carbide diagram ?

    The temperatures at which the phase changes occur are called critical points (or temperatures).

    45. Why PERT is preferred over CPM for evaluation of project ?

    PERT is based on the approach of multiple time estimates for each activity.

    46. What is the percentage of chromium in 18 : 4 : 1 IISS ?

    4%.

    47. What is stellite ?

    It is a non-ferrous cast alloy containing cobalt, chromium and tungsten.

    48. Which rays are produced by cobalt-60 in industrial radiography ?

    Gamma rays.

    49. What are killed steels and what for these are used ?

    Killed steels are deoxidised in the ladle with silicon and aluminium. On solidification no gas evolution occurs in these steels because they are free from oxygen.

    50. What is critical temperature in metals ?

    It is the temperature at which the phase change occurs in metals.

    51. Car tyres are usually made of ?

    Styrene-butadine rubber.

    52. What is the structure of pure iron and whether it is soft or hard ?

    Ferrite and it is soft.

    53. Which elements increase the corrosion resistance of steel ?

    Chromium and nickel.

    54. What causes hardness in steel ? How heat treatment alters properties of steel ?

    The shape and distribution of the carbides in the iron determines the hardness of the steel. Carbides can be dissolved in austenite is the basis of the heat treatment of steel. If steel is heated above the A critical temperature to dissolve all the carbides, and then cooled, suitable cooling through the cooling range will produce the desired size and distribution of carbides in the ferrite, imparting different properties.

    55. Explain the formation of microstructures of pearlite, bainite and martensite in steel.

    If austenite containing about 0.80 percent carbon is slowly cooled through the critical temperature, ferrite and cementite are rejected simultaneously, forming alternate plates or lamellae. This microstructure is called pearlite. At temperatures just belot the A1, the transformation from http://austenite.to pearlite may take an appreciable time to initiate and complete, but the product will be lameller pearlite. As the transformation temperature is lowered, the time to initiate transformation shortens but the product is pearlite of increasing fineness, and at temperatures approaching 550°C it cannot be resolved into its lamellar constituents. Further deerease in transformation temperature causes a lengthening of the ncubation period and a change in structure of the product to a form known as “bainite”.

    If the temperature is lowered sufficiently, the diffusion controlled nucleation and growth modes of transformation are suppressed completely and the austenite transforms by a diffusionless process in which the crystal lattice effectively shears to a new crystallographic configuration known as “martensite”. This phase has a tetragonal crystal structure and contains carbon in supersaturated solid solution.

    56. How with alloying of steel it is possible to a achieve properties which can not be achieved with heat treatment ?

    A prerequisite to the hardening of steels is that martensite should be formed on cooling, but this can only be achieved if the rate of cooling is great enough to suppress the formation of pearlite or bainite and in plain carbon steels this can be achieved by quenching relatively small specimens

    57. What are the major effects of alloying elements?

    1. To alter the transformation temperatures and times
    2. To modify the room temperature and elevated temperature strengths of given structures by (a) stiffening the crystals and (b) introducing complex precipitates which tend to harden the steel.
    3. To modify the type of oxide film formed on the surface of the steel and thereby affect its corrosion resistance.

    58. What is the difference between austenite stabilisers and ferrite stabilisers ?

    • Austenite stabilisers have the effect of extending the temperature range overwhich austenite is formed. Such elements are carbon, manganese, nickel, copper and cobalt.
    • Ferrite stabilisers have the effect of extending the temperature range over which alpha and delta ferrite are formed, which consequently reduces temperature range over which austenite is formed. Such elements are silicon, chromium, molybdenum, tungsten, titanium and niobium.

    59. What are the effects of carbon on the properties of steel.

    In general, an increase in carbon content produces higher ultimate strength and hardness but lowers ductility and toughness of steel alloys. Carbon also increases air-hardening tendencies and weld hardness, especially in the presence of chromium. In low-alloy steel for high-temperature applications, the carbon content is usually restricted to a maximum of about 0.15% in order to assure optimum ductility for welding, expanding, and bending operations. To minimize intergranular corrosion caused by carbide precipitation, the carbon content of austenitic (18-8 type) alloys is limited in commercial specifications to a maximum of 0.08%, or even less, i.e. 0.03% in the extremely low-carbon grades used in certain corrosion-resistant applications.

    In plain carbon steels in the normalised condition, the resistance to creep at temperatures below 440°C appears to increase with carbon content up to 0.4% carbon, at higher temperatures there is

    but little variation of creep properties with carbon content.

    An increase in carbon content lessens the thermal and electrical conductivities of steel and increases its hardness on quenching.

    60. What is the role of silicon as alloying element in steels ?

    Silicon contributes greatly to the production of sound steel because of its deoxidizing and degasifying properties. When added in amounts up to 2.5%, the ultimate strength of the steel is increased without loss in ductility. Silicon in excess of 2.5% causes brittleness, and amounts higher than 5% make the steel non-malleable.

    Resistance to oxidation and surface stability of steel are increased by the addition of silicon. These desirable effects partially compensate for the tendency of silicon to lower the creep properties of steel. Silicon increases the electrical resistivity of steel and decreases hysteresis losses.

    61. Discuss the role of manganese in alloying steels.

    Manganese is an excellent deoxidizer and sulfur neutralizer, and improves the mechanical properties of steel, notably the ratio of yield strength to tensile strength at normal temperatures. As an alloying element, manganese serves as an inexpensive means of preventing “hot shortness”. It improves rolling properties, hardenability, and resistance to wear. However manganese increases the crack sensitivity of weldments, particularly with steels of higher carbon content.

    62. Define buckling factor.

    It is the ratio of the equivalent length of column to the minimum radius of gyration.

    63. What do you understand by catenary cable ?

    A cable attached to the supports and carrying its own weight.

    64. What is coaxing ?

    It is the process of improving fatigue properties by first under-stressing and then increasing the stress in small increments.

    65. What is difference between conjugate beam and continuous beam ?

    • A conjugate beam is an imaginary beam of same size as original beam and carrying a distributed load in accordance with the bending moment diagram.
    • A continuous beam is one which is resting on more than two supports.

    66. What is isotropic material ?

    It is a material having same elastic constants in all directions.

    67. Explain difference between modulus of resilience and modulus of rigidity ?

    Modulus of resilience is the maximum strain energy stored in a material per unit volume and modulus of rigidity is the ratio of shearing stress to the shearing strain within the elastic limit.

    68. What is the difference between basic hole and basic shaft ?

    A basic hole is one whose lower deviation is zero and in case of basic shaft the upper deviation is zero.

    69. What for pyranometer is used ?

    It is used to measure the total hemispherical solar radiation.

    70. Describe transfer machines in brief.

    It is an automatic machine in which workpiece alongwith fixture is transferred from one station to other automatically and several operation on workpiece are performed at each station.

    71. What is burnt-out point ?

    It corresponds to maximum heat flux at which transition occurs from nucleate boiling to film boiling.

    72. What do you understand by eutectic ?

    It is mechanical mixture of two or more phases which solidify simultaneously from the liquid alloy.

    72. Explain the difference between grey iron and white iron. What is mottled iron ?

    The carbon in cast iron could exist at room temperature as either iron carbide, or as graphite which is the more stable form. Irons containing carbon as graphite are soft, easily machinable and are called “grey irons”. Irons with carbon present as iron carbide are extremely hard, difficult to machine and are called “white” irons. Irons with fairly equal proportions of graphite and iron carbide have intermediate hardness and are called “mottled” irons.

    73. The graphite in grey irons exists in the form of flakes which act as stress-raisers under tensile loading and consequently grey irons have relatively low tensile strength and ductility. Still grey iron is extensively used in engineering. Why ?

    Grey iron is extensively used in engineering because of following characteristics.

    1. Cheapness.
    2. Low melting point and high fluidity making it suitable for castings of intricate shape.
    3. Relatively good erosion and corrosion resistance.
    4. High damping capacity, with respect to vibration.
    5. Relatively good mechanical properties under compressive loading.

    74. Under what condition a convergent divergent nozzle required ?

    When pressure ratio is greater than critical pressure ratio.

    75. What is endurance limit and what is its value for steel ?

    Endurance limit is the maximum level of fluctuating stress which can be tolerated indefinitely. In most steels this stress is approximately 50% of the ultimate tensile strength and it is defined as the stress which can be endured for ten million reversals of stress.

    76. How the net work to drive a compressor and its volumetric efficiency behave with increase in clearance volume ?

    Work remains unaltered and volumetric efficiency decreases.

    77. What do you understand by sulphur print ?

    Sulphides, when attached with dilute acid, evolve hydrogen sulphide gas which stains bromide paper and therefore can be readily detected in ordinary steels and cast irons. While sulphur is not always as harmful as is sometimes supposed, a sulphur print is a ready guide to the distribution of segregated impurities in general.

    78. What is the different between brass and bronze ?

    Brass is an alloy of copper with zinc; and bronze is alloy of copper with tin.

    79. What is the effect of addition of zinc in copper? What is the use of 70/30 brass ?

    By addition of zinc in copper, both tensile strength and elongation increases. The 70/30 brass has excellent deep drawing property and is used for making radiator fins.

    80. What for admirality brass used ?

    Admirality brass with 29% zinc and 1% tin has good corrosion resistance and is used for condenser and feed heater tubes. Aluminium is also added to brass to improve corrosion resistance.

    81. What is the maximum use of magnesium ?

    Magnesium is used to alloy with aluminium and as an additive for making SG (Spheroidal Graphite) iron.

    82. What for zinc finds applications ?

    Galvanizing consumes the largest proportion of zinc. Zinc is resistant to corrosion but is attacked by acids and alkalies. Zinc alloy.s are suited for making die casting since the melting point is reasonably low.

    83. Which factors influence the type of fracture in failure of a material ?

    Seven factors influencing type of failure are :

    1. Type of material (inherent structure properties),
    2. Manner of loading (Static versus dynamic),
    3. Range of imposed stress,
    4. Strain rate (static, dynamic, impact),
    5. Stress distribution (discontinuity in material/shape),
    6. temperature, and
    7. surface treatment.

    84. What is the name given to ratio of actual cycle efficiency and ideal cycle efficiency.

    Efficiency ratio.

    85. List two effects of manganese in plain carbon steels.

    Manganese increases tensile strength and hardness. It decreases weldability.

    86. Name the strongest and weakest type of atomic bonds.

    Metallic bond is strongest and molecular bond also known as Vander Waals bond is weakest.

    87. In which process internal energy remains constant ?

    Isothermal process.

    88. What is temper embrittlement in alloy steels and what are its effects ?

    Embrittlement attack is usually intergranular in metals, i.e. cracks progress between the grains of the polycrystalline material. It imparts a tendency to fail under a static load after a given period of time in those alloy steels which are susceptible to embrittlement.

    89. What are whiskers ?

    Whiskers are very small crystals which are virtually free from imperfections and dislocations.

    90. What is Bauschinger effect ?

    According to Bauschinger, the limit of proportionality of material does not remain constant but varies according to the direction of stress under cyclic stresses.

    91. What is the difference between heat capacity and specific heat of a material ?

    Ans:

    • The heat capacity of a material is the amount of heat transformed to raise unit mass of a material 1 degree in temperature.
    • The specific heat of a material is the ratio of the amount of heat transferred to raise unit mass of a material 1 degree in temperature to that required to raise unit mass of water 1 degree of temperature at some specified temperature.
    • For most engineering purposes, heat capacities may be assumed numerically equal to;specific heats.

    92. Explain the rule to find specific heat of aqueous solutions.

    For aqueous solutions of salts, the specific heat can be estimated by assuming the specific heat of the solution equal to that of the water alone. Thus, for a 15% by weight solution of sodium chloride in water, the specific heat would be approximately 0.85.

    93. What do you understand by latent heat ? Give four examples of latent heats.

    For pure substances, the heat effects accompanying changes in state at constant pressure (no temperature change being evident) are known as latent heats. Examples of latent heats are : heat of fusion, vaporisation, sublimation, and change in crystal form.

    94. Define the terms free energy and free enthalpy. What is their significance and importance ?

    Free energy (or Helmholtz function) is defined as/= u -Ts.

    It is equal to the work during a constant-volume isothermal reversible nonflow process.

    Free enthalpy (or Gibbs function) is defined as g = h – Ts

    (where u = internal energy, h = enthalpy, T = temperature, s = entropy)

    Gibbs function is of particular importance in processes where chemical changes occur. For reversible isothermal steady-flow processes or for reversible constant-pressure isothermal nonflow processes, change in free energy is equal to net work.

    95.Which parameter remains constant in isochoric process ?

    Volume.

    96. What is polytropic process ? Under what conditions it approaches isobaric, isothermal, and isometric process ? In which reversible process no work is done ?

    A polytropic process is one that follows the equation pun = constant (index n may have values from – oc to + oo. This process approaches isobaric when n = 0, isothermal when n = 1, and isometric when n = . No work is done in isometric process.

    97. Whether superheated steam can be treated like ideal gas ?

    Yes.

    98. Out of constant pressure and constant volume lines on TS diagram which line has higher slope ? And whether slope is constant or variable ?

    Constant volume line. Slope is variable.

    99. Whether entropy is intensive property or extensive property ?

    Entropy is extensive property.

    100. In which process fluid expands but does no work ?

    Throttling process.

    101. What is the difference between scavenging and supercharging ?

    Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air.

    102. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes.

    Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively.

    103. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ?

    It will decrease.

    104. Why entropy change for a reversible adiabatic process is zero ?

    Because there is no heat transfer in this process.

    105. What are two essential conditions of perfect gas ?

    It satisfies equation of state and its specific heats are constant.

    106. Enthalpy and entropy are functions of one single parameter. Which is that ?

    Temperature.

    107. Why rate of condensation is higher on a polished surface compared to rusty surface ?

    Polished surface promotes drop wise condensation and does not wet the surface.

    108. How much resistance is offered to heat flow by drop wise condensation ?

    Nil

    109. What is the relationship between COP of heating and cooling ?

    COP of heating is one(unity) more than COP of cooling.

    110. How much is the work done in isochoric process ?

    Zero.

    111. When maximum discharge is obtained in nozzle ?

    At the critical pressure ratio.

    112. Under what condition the work done in reciprocating compressor will be least ?

    It is least when compression process approaches isothermal. For this purpose, attempts are made to cool the air during compression.

    113. What is the difference between stalling and surging in rotary compressions ?

    Stalling is a local phenomenon and it occurs when How breaks away from the blades. Surging causes complete breakdown of flow and as such it affects the whole machine.

    114. Why the electric motor of a fan with backward curved blades is never got overloaded under any condition ?

    The maximum power is consumed at about 70% of maximum flow in case’of fan with backward blades. For higher flow, power consumption gets lower.

    115. Why the work per kg of air flow in axial flow compressor is less compared to centrifugal compressor for same pressure ratio ?

    Isentropic efficiency of axial flow compressor is higher.

    116. What is the name given to portion of thermal energy to be necessarily rejected to environment ?

    Anergy.

    117. What is pitting ? How it is caused ?

    Non uniform corrosion over the entire metal surface, but occuring only in small pits is called pitting. It is caused by lack of uniformity in metal.

    118. What is caustic embrittlement ?

    It is the actual physical change in metal that makes it extremely brittle and filled with minute cracks. It occurs particularly in the seams of rivetted joints and around the rivet holes.

    119. Which impurities form hard scale and which impurities soft scale ?

    Sulphates and chlorides of lime and magnesium form hard scale, and carbonates of lime and magnesium form soft scale.

    120. What is the difference between hard water and soft water ?

    Hard water contains excess of scale forming impurities and soft water contains very little or no scale forming substances.

    121. Which two elements in feed water can cause corrosion of tubes and plates in boiler ?

    Acid and oxygen in feed water lead to corrosion.

    122. What should be done to prevent a safety valve to stick to its seat ?

    Safety valve should be blown off periodically so that no corrosion can take place on valve and valve seat.

    123. Why large boilers are water tube type ?

    Water tube boilers raise steam fast because of large heat transfer area and positive water circulation. Thus they respond faster to fluctuations in demand. Further single tube failure does not lead to catastrophy.

    124. What type of boiler does not need a steam drum ?

    Super-critical pressure boiler.

    125. Why manholes in vessels are usually elliptical in shape ?

    Elliptical shape has minimum area of opening and thus plate is weakened the least. Further it is very convenient to insert and take out the cover plate from elliptical opening.

    126. Low water in boiler drum is unsafe because it may result in overheating of water tubes in furnace. Why it is unsafe to have high water condition in boiler drum ?

    High drum level does not allow steam separation to be effective and some water can be carried over with steam which is not desirable for steam turbine.

    127. Why boiler is purged every time before starting firing of fuel ?

    Purging ensures that any unburnt fuel in furnace is removed, otherwise it may lead to explosion.

    128. What is the principle of mechanical refrigeration ?

    Axis. A volatile liquid will boil under the proper conditions and in so doing will absorb heat from surrounding objects.

    129. Why high latent heat of vaporisation is desirable in a refrigerant ?

    A high latent heat of vaporisation of refrigerant results in small amount of refrigerant and thus lesser circulation system of refrigerant for same tonnage.

    130. What is the critical temperature of a refrigerant ?

    Critical temperature is the maximum temperature of a refrigerantrat which it can be condensed into liquid and beyond this it remains gas irrespective of pressure applied.

    131. Maximum combustion temperature in gas turbines is of the order of 1100 to 10°C whereas same is around 00°C in I.C. engine ? Why ?

    High temperature in I.C. engine can be tolerated because it lasts for a fraction of second but gas turbines have to face it continuously which metals can’t withstand.

    132. Why efficiency of gas turbines is lower compared to I.C. engines ?

    In gas turbines, 70% of the output of gas turbine is consumed by compressor. I.C. engines have much lower auxiliary consumption. Further combustion temperature of I.C. engines is much higher compared to gas turbine.

    133. What do you understand by timed cylinder lubrication ?

    For effective lubrication, lub oil needs to be injected between two piston rings when piston is at bottom of stroke so that piston rides in oi during upward movement. This way lot of lub oil can be saved and used properly.

    134. What is IIUCR in relation to petrol engine ?

    HUCR is highest useful compression ratio at which the fuel can be used in a specific test engine, under specified operating conditions, without knocking.

    135. In some engines glycerine is used in place of water for cooling of engine. Why ?

    Glycerine has boiling point of 90°C which increases its heat carrying capacity. Thus weight of coolant gets reduced and smaller riadiator can be used.

    136. Why consumption of lubricating oil is more in two-stroke cycle petrol engine than four-stroke cycle petrol engine ?

    In two-stroke engine lub oil is mixed with petrol and thus some lub oil is blown out through the exhaust valves by scavenging and charging air. There is no such wastage in four stroke petrol engine.

    137. As compression ratio increases, thermal n increases. How is thermal n affected by weak and rich mixture strength ?

    Thermal n is high for weak mixture and it decreases as mixture strength becomes rich.

    138. How engine design needs to be changed to burn lean mixture ?

    Engine to burn lean mixture uses high compression ratio and the highly turbulent movement of the charge is produced by the geometry of the combustion chamber.

    139. Horse power of I.C. engines can be expressed as RAC rating, SAE rating, or DIN rating. To which countries these standards belong ?

    U.K., USA and Germany respectively.

    140. What is the use of flash chamber in a vapour compression refrigeration cycle to improve the COP of refrigeration cycle ?

    When liquid refrigerant as obtained from condenser is throttled, there are some vapours. These vapours if carried through the evaporator will not contribute to refrigerating effect. Using a flash chamber at some intermediate pressure, the flash vapour at this pressure can be bled off and fed back to the compression process. The throttling process is then carried out in stages. Similarly compression process is also done in two separate compressor stages.

    141. Why pistons are usually dished at top ?

    Pistons are usually hollowed at top to (i) provide greater spa’e for combustion, (ii) increase surface for flue gases to act upon, and (iii) better distribution of stresses.

    142. What is the function of thermostat in cooling system of an engine ?

    Thermostat ensures optimum cooling because excessive cooling decreases the overall efficiency. It allows cooling water to go to radiator beyond a predetermined temperature.

    143. What are the causes of failure of boiler tubes ?

    Boiler tubes, usually are made from carbon steel and are subject to (a) high rates of heat transfer, (b) bending stresses due to uneven heating, especially at expanded or welded joints into headers or drums, (c) external erosion from burners and flue gas, (d) possible corrosion on the boiler side, and (e) occasional manufacturing defects.

    Failure may occur due to following reasons :

    (a) High thermal ratings may lead to rapid failure if the internal fluid flow is reduced for any reason. The resultant overheating leads to a failure by creep, characterised by the bulging of the tube with the eventual development of a longitudinal split.

    (b) Fatigue cracking due to bending stresses occur. These are associated with change of section and/or weld undercut, where tubes are expanded or welded into headers.

    (c) Failure may arise due to overstressing of a reduced section of metal.

    (d) Sudden failure of the boiler tube due to corrosion arises from embrittlement of the carbon steel due to interaction between atomic hydrogen from the corrosion process and the iron carbide present in the steel.

    (e) Defects in tube manufacture, although far from being a regular occurrence, can be a cause of serious trouble. Lamination in boiler tubes or score marks arising from the cold drawing of tubes, give rise to premature failure and may promote corrosion at these regions.

    144. What are the causes of failure of superheater tubes ?

    Superheater tubes are subjected to the most severe combination of stress, temperature and corrosive environment. In addition to high-temperature strength, resistance to corrosion is also important. For example, low-alloy ferritic steel such as -1/% Cr, 1% Mo would not be used at metal temperatures above 580°C because of inadequate resistance to corrosion and oxidation over a full service life of 100,000/150,000 hr.

    Failures in superheater tubes may arise from :

    (a) Prior fabrication history (b) Faulty heat treatment

    (c) Consequences of welding (d) Overheating of the tube metal

    (e) Gas-side corrosion (f) Stress corrosion (austenitic steels).

    145. Why supercritical boilers use less amount of steel compared to non-supercritical boilers ?

    Supercritical boilers do not head heavy drum for separation of steam from mixture of water and steam.

    146. Out of electric heater and heat pump, which is economical in operation ?

    Heat pump.

    147. Which furnace burns low-ash fusion coal and retains most of the coal ash in the slag?

    Cyclone furnace.

    148. How the thickness of thermal boundary layer and thickness of hydrodynamic boundary layer related ?

    Ratio of their thickness = (Prandtl number)-1/3.

    149. What is the effect of friction on flow of steam through a nozzle ?

    To decrease both mass flow rate and wetness of steam.

    150. Why gas turbine power plant needs efficient compressor ?

    Because a large portion of turbine work is eaten away by compressor and its inefficiency will affect net power output and cost of generation.

    151. Why rockets using liquid hydrogen have higher specific impulse compared to liquid hydrocarbon ?

    Liquid hydrogen has higher burning velocity.

    152. Why axial flow compressor is preferred for gas turbines for aeroplanes ?

    Because it has low frontal area.

    153. What is the effect of inter cooling in gas turbines ?

    It decreases thermal efficiency but increases net output.

    154. Why iso-octane is chosen as reference fuel for S.I. engines and allotted 100 value for its octane number ?

    Iso-octane permits highest compression without causing knocking.

    155. Why thermal efficiency of I.C. engines is more than that of gas turbine plant ?

    In I.C. engine maximum temperature attained is higher than in gas turbine.

    156. Which are the reference fuels for knock rating of S.I. engines ?

    n-heptane and ISO-octane.

    157. When effect of variations in specific heats is considered then how do maximum temperature and pressure vary compared to air standard cycle ?

    Temperature increases and pressure decreases.

    158. Quantities like pressure, temperature, density, viscosity, etc. are independent of mass. What are these called ?

    Intensive properties.

    159. The amount of radiation emitted per scm per sec is called …. ?

    Emissive power.

    160. In convection heat transfer, if heat flux intensity is doubled then temperature difference between solid surface and fluid will ?

    Get doubled.

    161. How you can define coal ?

    Coal is a naturally occurring hydrocarbon that consists of the fossilised remains of buried plant debris that have undergone progressive physical and chemical alteration, called coalification, in the course of geologic time.

    162. Which pollutant is major greenhouse gas and what is its effect ?

    CO is major greenhouse gas and it traps the radiation of heat from the sun within earth’s atmosphere.

    163. In order to increase efficiency and reduce CO emissions and other emissions, clear coal technologies are receiving major attention. What are these ?

    (i) Advanced pulverised and pressurised pulverised fuel combustion.

    (ii) Atmospheric fluidised bed combustion and pressurised fluidised bed combustion.

    (iii) Supercritical boilers.

    (iv) Integrated gasification combined cycle systems.

    (v) Advanced integrated gasification, including fuel cell systems.

    (vi) Magneto hydrodynamic electricity generation.

    164. What are the important operational performance parameters in design of fuel firing equipment ?

    Fuel flexibility, electrical load following capability, reliability, availability, and maintenance ease.

    165. What is the difference between total moisture and inherent moisture in coal ?

    The moisture content of the bulk as sampled is referred to as total moisture, and that of the air dried sample is called inherent moisture.

    166. Proximity analysis of coal provides data for a first, general assessment of a coal’s quality and type. What elements it reports ?

    Moisture, volatile matter, ash and fixed carbon.

    167. Ultimate analysis of coal is elementary analysis. What it is concerned with ?

    Carbon, hydrogen, nitrogen, and sulphur in coal on a weight percentage basis.

    168. Explain the difference between AFBC, BFBC, PFBC and PCFB in regard to fluidised bed technologies.

    AFBC (Atmospheric fluidised bed combustion) process consists of forming a bed of inert materials like finely sized ash or ash mixed with sand, limestone (for sulphur removal), and solid fuel particles in a combustor and fluidising it by forcing combustion air up through the bed mixture. The gas flows thorugh bed without disturbing particles significantly but gas velocity is high enough to support the total weight of bed (fluidisation). At slightly higher velocity excess gas passes through the bed as bubbles (fluidised bed) and gives the bed the appearance of a boiling liquid.

    Bubbling fluidised bed combustion (BFBC) has a defined height of bed material and operates at or near atmospheric pressure in the furnace.

    Pressurised fluidised bed combustion (PFBC) system operates the bed at elevated pressure. Exhaust gases have sufficient energy to power a gas turbine, of course, gases need to be cleaned.

    In fluidised combustion, as ash is removed some unburned carbon is also removed resulting in lower efficiency. In circulating fluidised bed combustion (CFBC) system, bed is operated at higher pressure leading to high heat transfer, higher combustion efficiency, and better fuel feed. Circulating fluidised beds operate with relatively high gas velocities and fine particle sizes. The maintenance of steady state conditions in a fast fluidised bed requires the continuous recycle of particles removed by the gas stream (circulating bed). The term circulating bed is often used to include fluidised bed systems containing multiple conventional bubbling beds between which bed material is exchanged.

    169. What for Schmidt plot for is used in heat transfer problems ?

    Schmidt plot is a graphical method for determining the temperature at any point in a body at a specified time during the transient heating or cooling period.

    170. In which reactor the coolant and moderator are the same ?

    Pressurised water reactor.

    171. Which reactor has no moderator ?

    Fast breeder reactor.

    172. What are thermal neutrons ?

    Thermal neutrons are slow neutrons (having energy below 1 eV) which are in thermal equilibrium with their surroundings.

    173. What is big advantage of fast breeder reactor ?

    It has rapid self breeding of fissile fuel during the operation of the reactor, and thus, it offers about sixty times the output with same natural uranium resources through ordinary non-breeder nuclear reactor.

    174. What is the purpose of biological shield in nuclear plants ?

    Biological shield of heavy concrete prevents exposure to neutrons, beta rays and gamma rays which kill living things.

    175. Which two elements have same percentage in proximate and ultimate analysis of coal?

    Moisture and ash.

    176. On which analysis is based the Dulong’s formula for the heating value of fuel ?

    On ultimate analysis.

    177. Which element causes difference in higher and lower heating values of fuel ?

    Hydrogen.

    178. Which heating value is indicated by a calorimeter and why ?

    Gross heating value because steam is condensed and heat of vapour formed is recovered.

    179. State the difference between ultimate and proximate analysis of coal ?

    In ultimate analysis, chemical determination of following elements is made by weight: Fixed and combined carbon, H, O, N, S, water and ash. Heating value is due to C, H and S.

    In proximate analysis following constituents are mechanically determined by weight. Moisture, volatile matter, fixed carbon and ash. Heating value is due to fixed carbon and volatile matter.

    180. What is fuel ratio ?

    Fuel ratio is the ratio of its % age of fixed carbon to volatile matter.

    181. How the analyses and calorific values of fuels can be reported ?

    It may be reported as

    (a) as received or fired (wet) basis

    (b) dry or moisture free basis

    (c) combustible or ash and moisture free basis

    182. What is the difference between nuclear fission and fission chain reaction.

    The process of splitting of nucleus into two almost equal fragments accompanied by release of heat is nuclear fission. Self sustained, continuing, sequence of fission reactions in a controlled manner is fission chain reaction.

    183. Explain difference between fissile and fertile materials.

    The materials which can give nuclear fission e.g. U 35, Pu 39, U 33 are fissile materials. Fertile material itself is not fissionable, but it can be converted to a fissionable material by irradiation of neutrons in a nuclear reactor.

    184. What do you understand by fuel cycle in nuclear plants ?

    Fuel cycle a series of sequential steps involved in supplying fuel to a nuclear power reactor. The steps include : Mining, refining uranium, fabrication of fuel elements, their use in nuclear reactor, chemical processing to recover remaining fissionable material, re-enrichment of fuel from recovered material, refabrication of new fuel elements, waste storage etc.

    185. What is heavy water and what is its use in nuclear plants ?

    Water containing heavy isotopes of hydrogen (Deuterium) is known as heavy water. Heavy water is used as a moderator. Heavy water has low cross section for absorption of neutrons than ordinary water. Heavy water slows down the fast neutrons and thus moderates the chain reaction.

    186. What is a converter reactor ?

    A reactor plant which is designed to produce more fuel than it consumes. The breeding is obtained by converting fertile material to fissile material.

    187. Explain nuclear reactor in brief.

    A plant which initiates, sustains, controls and maintains nuclear fission chain reaction and provides shielding against radioactive radiation is nuclear reactor.

    188. What is the difference between conversion and enrichment ?

    Ans:

    • The process of converting the non fissile U 38 to fissile U-35 is also called “Conversion”. The material like U 38 which can be converted to a fissile material by the neutron flux is called “fertile material”. The conversion is obtained within the nuclear reactor during the chain reaction.
    • Enrichment is the process by which the proportion of fissile uranium isotope (U-35) is increased above 0.7% (original % in natural uranium).
    • The concentration of U-35 in the uranium hexafluoride is increased from the 0.7% in natural uranium to to 4%. This is called enrichment and is accomplished in an enrichment plant.

    189. Disposal of radioactive waste materials and spent fuel is a major and important technology. How the waste radioactive material is disposed off ?

    Nonusable fission products are radioactive and take short/medium/long time for radioactive decay to reach safe level of radioactivity. Accordingly three methods of disposal are :

    (a) Zero or low radioactivity material is dispersed or stored without elaborate shielding.

    (b) Medium radioactivity material is stored for short duration of about 5 years to allow decay of radioactivity.

    (c) High radioactive material. They are stored in water for several months to permit radioactive decay to an accepetable low level.

    190. Which nuclear reactor uses water as a coolant, moderator and reflector ?

    Pressurised water reactor.

    191. Which reactor produces more fissionable material than it consumes ?

    Breeder reactor.

    192. Which reactor uses natural uranium as fuel ?

    Gas cooled reacator.

    193. Which reactor uses heavy water as moderator ?

    CANDU.

    194. Which reactor requires no moderator ?

    Breeder reactor.

    195. Which reactor uses primary coolant as fluoride salts of lithium, beryllium, thorium and uranium ?

    Molten salt breeder reactor.

    196. Why an increase in area is required to produce an increase of velocity in case of supersonic flow ?

    Increase in area for increase in velocity for supersonic flow is required because the density decreases faster than velocity increases at supersonic speeds and to maintain continuity of mass, area must increase.

    197. Under what circumstances would there be an increase in pressure in a divergent nozzle ?

    For subsonic flow at inlet section of a diffuser a lower velocity and higher pressure will exist at the exit section. For supersonic isentropic flow at the inlet section a higher velocity and lower pressure will exist at the exit but if a shock wave occurs in the diffuser then a higher pressure will exist at the exit.

    198. Why water can’t be used as refrigerant for small refrigerating equipment ?

    The refrigerant should be such that vapour volume is low so that pumping work will be low. Water vapour volume is around 4000 times compared to R- for a given mass.

    199. Which parameter remains constant in a throttling process ?

    Enthalpy.

    200. What is the difference between isentropic process and throttlinglprocess ?

    In isentropic process, heat transfer takes place and in throttling process, enthalpy before and after the process is same.

    • Q. What is a CI engine and a SI engine? How do they differentiate from one another?
    • Q. How does an Air Conditioner works?

    (followed by)

    • Q. How does a compressor functions?
    • Q. What are HVACs?
    • Q. What will happen if we use petrol in a CI engine?
    • What is CVT, dtsi, CRDI?

    Then some basic questions from IT and programming

    • Q.What is 's' in HTTPS?
    • Q.Write the algorithm to print the reverse of a number in c++?
    • Q. Write the algorithm to print alternate prime numbers.
    • Q. What is stacking? Give example.
    • Q.What is the approach follwed by c? TOP DOWN or BOTTOM UP?
    • Q.What is sorting? What is a bubble sort?
    • Q.What is Round Robin Scheduling?
    • Q.What does SDLC stands for?

    There were some more from programming…
    Then some general questions..

    • What is ISIS?
    • What do you think about the "MAKE IN INDIA" programme of government?

    Then the last question:-

    • Why did you opt for Mechanical Engineering?

    This interview was for ..INFOSYS.

  18. Company : MDL (Mazagon Dock Limited)

    Questions :
    Q: Tell me something about yourself and your family background.
    me : told.

    Q: Which city in Nepal is attached to the  border of Bihar ?
    me: I didn't knew (They told me it's Birganj )

    Q: Give us an overview of your summer internship. What was its practical application? Try to keep it as short as possible.
    me: told

    Q: What was you B.Tech project about? Explain in detail.
    me: told.

    Q: What does MDL (company's name) do?
    me: It makes warships, ship buildings and offshore vessels for companies like ONGC.

    Q: Apart from MDL where else have you applied for?
    me: ONGC, NTPC, IOCL and BARC.

    Q: Tell me your area of interest?
    me: Thermodynamics and fluid mechanics (they started laughing because this was the area of interest common in more than 90% candidates they interviewed)

    Q: Draw the P-V and T-S diagram of otto cycle. What does 'S' in 'T-S' stands for?
    me:

     'S' stands for entropy.

    Q: Out of 4 stroke and 2 stroke SI engine, which one has better fuel efficiency? What about Power efficiency?
    me:  fuel efficiency of 4 stroke is better and power efficiency of 2 stroke is better.
          
    Q: So it's my final question. Suppose if you get selected in any of the above companies, would you prefer MDL over these companies?
    me: Sir both,my internship as well as my B.Tech project, were based on design and I would like to join a company which allows me to explore in this field, so I will surely join mdl because there is not much to explore in design field  in the above mentioned companies.   (They seem pretty satisfied with my answer)

    Advice : Thoroughly prepare your B.Tech Project and summer internship. It consumes about 70% of the total interview duration. Prepare Fluid mechanics, IC engines and Manufacturing for technical.  Be ready with your answers for HR questions.

    EDIT: I was selected.

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