Mechanical and Automobile Engineering Interview Questions

Replies

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  PuneetVerma

  What happens if gasoline is used in a
  Diesel engine?Diesel engine will work ?
  
  No, It will not work,as the Compression ratio of
  Petrol engine is 6 to 10 & that of Diesel engine
  is 15 to 22. Thus on such high compression,
  gasoline gets highly compressed & it may blast.
• 

  PuneetVerma

  Which Mechanism is used in
  Automobile gearing system ?
  
  Differential mechanism
  
  
  Why different types of sound are
  produced in different bikes though
  they say run on SI engine ?
  
  Engine specifications are different in different
  manufactures like as Bore Diameter(CC),
  Ignition timing.Also the exhaust
• 

  PuneetVerma

  Why entropy decreases with the
  increase in temperature?
  
  ds=dQ/TEntropy is inversely proportional to
  the temperature so.as temp. increases,entropy
  decreases.
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  PuneetVerma

  1 hp how much watt?
  746.2Watt
• 

  PuneetVerma

  How to calculate bearing number to
  diameter of the inner and outer ?
  
  Divide the shaft diameter size by 5, it will give
  last two digitof the bearing no. and according
  to type of load we have tochose the type
  of bearing and that will give prior no. ofthe
  bearing.
• 

  ganesh kalkutaki

  Amongs these two which have grater elasticity? Steel or rubber. ans- steel. because steel have grater youngs modulus elasticity than rubber. steel- 200GPA rubber-106N/M2
• 

  dhamu91

  what is seeback effect?
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  PuneetVerma

  Definition of Octane number & Cetane
  number
  Octane No.- Octane number is defined as the
  percentage, by volume, of iso octane in the
  mixture of iso octane and h-heptane. It is the
  measure of rating of SI engine.
  Cetane No.- Cetane number is defined as
  the percentage, by volume, of n-cetane in
  the mixture of n-cetane and alpha methyl
  naphthalene. It is the measure of rating of CI
  engine.
• 

  PuneetVerma

  Poisons ratio is higher in (rubber/
  steel/wood) ??
  When a material is compressed in one
  direction, it usuallytends to expand in the other
  two directions perpendicular tothe direction
  of compression. This phenomenon is called
  thePoisson effect. Poisson’s ratio is a measure
  of the Poisson effect.
  For rubber = 0.5
  For steel = 0.288
  For wood < 0.2
  Thus Poisson’s ratio is higher in RUBBER.
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  PuneetVerma

  The Fatigue life of a part can be improved
  by ?
  Improving the surface finish by Polishing &
  providing residual stress by Shot peening.
• 

  zaveri

  This question was asked to a guy, who specified his area of interest in his C.V as "power plant engineering".
  
  A wind turbine helps to generate electricity. so does a still ceiling fan rotating due to the passing wind, generate any power. ?
  
  No it does not, because, the fan motor is a single phase induction motor, and A.C motors , unlike D.C motors cannot be used as alternators.
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  NAVATHE SACHIN

  How to know whether the valve is inlet or exhaust by seeing the engine?
  Inlet valve has more diameter than exhaust valve.
• 

  NAVATHE SACHIN

  steam engine is discovered by jameswatt
• 

  NAVATHE SACHIN

  what is the rpm of steam engine?
  200rpm
• 

  NAVATHE SACHIN

  Is cooling is necessary in the engines?
  yes, cooling is necessary in the engines to satisfy the second law of thermodynamics.
• 

  NAVATHE SACHIN

  Is two strokes engines are suitable for S.I engines?
  No,two stroke engines are not suitable for s.i engines, because loss of fuel is more during scavenging process
• 

  CE Designer

  I was asked in my interview a very basic question yet I panicked.
  What are the different classes of metal alloys?
• 

  zaveri

  CE Designer

  I was asked in my interview a very basic question yet I panicked.
  What are the different classes of metal alloys?

  and what is the answer to that (i am panicking too).
  
  is it ferrous alloys and non-ferrous alloys ?
• 

  CE Designer

  😀 Yes Ferrous ( cast iron---carbon steels---high alloy steel (tool steel & stainless steel)
  and Non Ferrous like Aluminium, Copper, Magnesium, Titanium, Zinc...
• 

  PuneetVerma

  What is the difference between BSP
  thread and BSW thread?
  The British Standard Pipe thread (BSP thread) is
  a family of standard screw thread types that has been
  adopted internationally for interconnecting and sealing
  pipe ends by mating an external (male) with an internal
  (female) thread.
  
  British Standard Whitworth (BSW) is one of a
  number of imperial unit based screw thread standards
  which use the same bolt heads and nut hexagonal sizes.
• 

  PuneetVerma

  How Cavitation can be eliminated in a
  Pump?
  Cavitation means bubbles are forming in the
  liquid.
  · To avoid Cavitation, we have to increase the
  Pump size to One or Two Inch;
  · To increase the pressure of the Suction Head,
  or
  · Decrease the Pump Speed.
• 

  PuneetVerma

  Which pump is more efficient Centrifugal
  pump or Reciprocating pump?
  Centrifugal pump.
  Because flow rate is higher compared to
  reciprocating pump. Flow is smooth and it
  requires less space to install. Lower initial cost
  and lower maintenance cost.
• 

  PuneetVerma

  Why Centrifugal Pump is not called as a
  Positive Displacement Type of Pump?
  The centrifugal has varying flow depending
  on pressure or head, whereas the Positive
  Displacement pump has more or less constant
  flow regardless of pressure.
  Likewise viscosity is constant for positive
  displacement pump where centrifugal pump
  have up and down value because the higher
  viscosity liquids fill the clearances of the pump
  causing a higher volumetric efficiency. When
  there is a viscosity change in supply there is also
  greater loss in the system. This means change in
  pump flow affected by the pressure change.
  One more example is, positive displacement
  pump has more or less constant efficiency,
  where centrifugal pump has varying efficiency
  rate.
• 

  PuneetVerma

  Why cavitation will occur in Centrifugal
  Pumps and not in Displacement pumps?
  The formation of cavities (or bubbles) is induced
  by flow separation, or non-uniform flow
  velocities, inside a pump casing. In centrifugal
  pumps the eye of the pump impeller is smaller
  than the flow area of pipe. This decrease in flow
  area of pump results in increase in flow rate. So
  pressure drop happened between pump suction
  and the vanes of the impeller. Here air bubbles
  or cavities are formed because of liquid vapour
  due to increase in temperature in impeller.
  This air bubbles are transmitted to pump which
  forms cavitation.
• 

  PRASENJIT TOMAR

  NIce work ...... helpfull stuff... thanx...
• 

  serawit

  How do you get the belt number for standard v belt surrounding two pulleys?
  Answer:
  the circumference of the imaginary belt line surrounding the pulleys in inches is the belt number.
• 

  zaveri

  Itspuneet

  Why cavitation will occur in Centrifugal
  Pumps and not in Displacement pumps?
  The formation of cavities (or bubbles) is induced
  by flow separation, or non-uniform flow
  velocities, inside a pump casing. In centrifugal
  pumps the eye of the pump impeller is smaller
  than the flow area of pipe. This decrease in flow
  area of pump results in increase in flow rate. So
  pressure drop happened between pump suction
  and the vanes of the impeller. Here air bubbles
  or cavities are formed because of liquid vapour
  due to increase in temperature in impeller.
  This air bubbles are transmitted to pump which
  forms cavitation.

  a much simple answer to this is, that centrifugal is a dynamic type of pump.
• 

  ankush sharma

  here i also attached a file related to interview questions for mechanical engineer.
• 

  gopi gulivindala

  dhamu91

  what is seeback effect?

  when two bodies are different temparature i.e. hot&cold.if they are connected by wires(thermo couple) power will genarate.
• 

  The myth buster

  How can this be possible..so are saying that with the increase in temperature, ds becomes negative..but this isn't possible..as for any process to occur, ds shoulb be greater than or equal to zero..so it's not correct to say that entropy decreases with temperature rise..rather in the ds term there is a term for entropy generation..which settle this issue..this term is always positive or zero and keeps the total entropy change >=0.
• 

  Sarathkumar Chandrasekaran

  What is meant by the term "OVERDRIVE" in automobile?
  It is a term describing the process where the drive shaft speed is more than that of engine shaft speed.So attaining our target speed without stressing the engine to run to its peak speed.It also helps in minimizing the wear of engine as we are using it in optimum performance without high fatigue and also increase efficiency as the fuel consumption is decreased.
• 

  Ankita Katdare

  Here are some of the frequently asked questions:
  
  Explain the reason why big tyres are used in rear of vehicles.
  
  Explain the basic difference between BS2 and BS3 engine.
  
  What is an injector pressure in heavy vehicles? Why it is used?
  
  During the drive torque, what will be the weight shift?
  
  In a tractor, how the hydrostatic propulsion systems work?
  
  What is the range of engine efficiency in case of two stroke engine?
  
  What is back compressor in engines?
  
  What is octane number and cetane number?
  
  What is the reason for emitting the white exhaust smoke during start of the vehicle? How will you prevent this?
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  Satyendr yadav

  PuneetVerma

  Hi..
  
  In this thread I will be posting some popular Mechanical Interview Question and there answers too..
  
  Just Click Watch Thread for future updates to this thread.

  My BEL mechanical interview is on 14 September... Can you suggest something for interview.... Thnx in advance
• 

  vhes

  Nice thread:

  Some of good interview Questions are available here on mechanical design 

• 

  Tarun pal

  i think pre combustion ahead 

• 

  Abhay Pandey

  If any one have an idea which types of questions asked in engine maintenance engineer please share questions with answer  ,thanks 

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  Hassan Ndaliro

  I     am much happy with the Interview questions & answers that you have given here.