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50 Best Mechanical Engineering Interview Questions & Answers PDF Download

Mechanical Engineering Interview Questions

After completion the written exam, the recruiters conduct the Interview round. Candidates, who effectively reach final stage and don’t want to lose this opportunity, can start their preparation for interview round by the help of Best Mechanical Engineering Interview Questions & Answers given below.

Mechanical Engineering Interview Questions are tough from the other branches. So, candidates who have qualify mechanical Engineering exam and now searching for 50 Best Mechanical Engineering Interview Questions & Answers for Interview round are at correct path. We have given PDF links of Mechanical Engineering Interview Questions on this page.

On this page of we have also presented most common mechanical engineering interview questions for freshers in pdf format which will definitely help them for preparation of HR as well as technical rounds of the process.

Mechanical Engineering Interview Questions

Candidates need to go through Mechanical Engineering Interview Questions and Answers for Interview which is given below for their better preparation. Candidates who want to qualify final round that is Interview can prepare in better way with the help of below given Basic Mechanical Engineering Interview Questions And Answers.

Latest Mechanical Engineering Interview Questions

Question 1: What is the difference between scavenging and supercharging?

Answer: 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.

Question 2:  What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes?

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

Question 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?

Answer: It will decrease.

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

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

Question 5: What are two essential conditions of perfect gas?

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

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

Answer: Temperature.

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

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

Question 8: How much resistance is offered to heat flow by drop wise condensation ?

Answer: Nil

Question 9: What is the relationship between COP of heating and cooling ?

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

Question 10: How much is the work done in isochoric process ?

Answer: Zero.

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Mechanical Engineering Interview Questions And Answers

Question 11: When maximum discharge is obtained in nozzle?

Answer: At the critical pressure ratio

Question 12: Under what condition the work done in reciprocating compressor will be least?

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

Question 13: What is the difference between stalling and surging in rotary compressions?

Answer: 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.

Question 14: Why the electric motor of a fan with backward curved blades is never got overloaded under any condition?

Answer: 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.

Question 15: Why the work per kg of air flow in axial flow compressor is less compared to centrifugal compressor for same pressure ratio?

Answer: Isentropic efficiency of axial flow compressor is higher.

Question 16:  What is the name given to portion of thermal energy to be necessarily rejected to environment?

Answer: Energy

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Question 17: What is pitting? How it is caused?

Answer: 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.

Question 18: What is caustic embrittlement ?

Answer: 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.

Question 19: Which impurities form hard scale and which impurities soft scale ?

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

Question 20: 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.
  • Acid and oxygen in feed water lead to corrosion.

Basic Mechanical Engineering Interview Questions

Question 21: What should be done to prevent a safety valve to stick to its seat ?

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

Question 22: Why large boilers are water tube type ?

Answer: 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.

Question 23: What type of boiler does not need a steam drum ?

Answer: Super-critical pressure boiler.

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Question 24: Why manholes in vessels are usually elliptical in shape ?

Answer: 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.

Question 25:  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 ?

Answer: 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.

Question 26: Why boiler is purged everytime before starting firing of fuel ?

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

Question 27: What is the principle of mechanical refrigeration ?

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

Question 28: Why high latent heat of vaporisation is desirable in a refrigerant ?

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

Question 29: What is the critical temperature of a refrigerant ?

Answer: 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.

Question 30: Explain the second law of thermodynamics.

Answer: The entropy of the universe increases over time and moves towards a maximum value.

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Interview Questions For Mechanical Engineering

Question 31:  What kinds of pipes are used for steam lines?

Answer: 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.

Question 31: What is the difference between shear center flexural center of twist and elastic center?

Answer: 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.

Question 32: What is ferrite?

Answer: Magnetic iron rock

Question 33: What is the difference between projectile motion and a rocket motion?

Answer: 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.

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Question 34: What is a cotter joint?

Answer: 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.

Question 35: What is the alloy of tin and lead?

Answer: 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.

Question 36: What does F.O.F. stand for in piping design?

Answer: FOF stands for Face of Flange. A flange has either of the two types of faces:

  • Raised face
  • 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.

Question 37: Explain Otto cycle.

Answer: 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.

Question 38: What is gear ratio?

Answer: It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

Question 39: What is annealing?

Answer: 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.

Question 40: What is ductile-brittle transition temperature?

Answer: 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.

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Mechanical Engineering Interview Questions And Answers Book

Question 41: What is a uniformly distributed load?

Answer: 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.

Question 42: What are the differences between pneumatics and hydraulics?


  • Working fluid: Pneumatics use air, Hydraulics use Oil
  • Power: Pneumatic power less than hydraulic power
  • Size: P components are smaller than H components
  • Leakage: Leaks in hydraulics cause fluid to be sticking around the components. In pneumatics, air is leaked into the atmosphere.
  • Pneumatics obtain power from an air compressor while hydraulics require a pump
  • Air is compressible, hydraulic oil is not

Question 43: What is enthalpy?

Answer: Enthalpy is the heat content of a chemical system.

Question 44: What is a positive displacement pump?

Answer: 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.

Question 45: Why would you use hydraulics rather than pneumatics?

Answer: 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.

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Question 46: What is isometric drawing?

Answer: It is a 3-D drawing used by draftsmen, architects etc

Question 47: 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.

Question 48: Which conducts heat faster steel copper or brass?

Answer: 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.

Question 49: What is representative elementary volume?

Answer: Smallest volume over which measurements can be made that will yield a representative of the whole.

Question 50: Why are LNG pipes curved?

Answer: LNG pipes are curved because LNG is condensed gas (-164 deg cel) so it can expand the pipes that is what engineers designed the LNG pipes are curve type.

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Mechanical Engineering Interview Questions And Answers PDF

Basic Mechanical Engineering Interview Questions And Answers PDF

About Mechanical Engineering

Mechanical engineering is the discipline that applies to the engineering, physics, and materials science principles to design, analyze, manufacture, and maintain mechanical systems. Mechanical Engineering is one of the oldest of the engineering disciplines.

Fundamental subjects of mechanical engineering:

  • Mathematics (in particular, calculus, differential equations, and linear algebra)
  • Basic physical sciences (including physics and chemistry)
  • Statics and dynamics
  • Strength of materials and solid mechanics
  • Materials Engineering, Composites
  • Thermodynamics, heat transfer, energy conversion, and HVAC
  • Fuels, combustion, Internal combustion engine
  • Fluid mechanics (including fluid statics and fluid dynamics)
  • Mechanism and Machine design (including kinematics and dynamics)
  • Instrumentation and measurement
  • Manufacturing engineering, technology, or processes
  • Vibration, control theory and control engineering
  • Hydraulics, and pneumatics
  • Mechatronics, and robotics
  • Engineering design and product design
  • Drafting, computer-aided design (CAD) and computer-aided manufacturing (CAM)

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What is the work of Mechanical Engineer?

All the Mechanical engineers examine, design, develop, build, and also test a mechanical as well thermal device that includes tools, engines, and machines. Generally, Mechanical engineers do the work which is given below here.

  • To analyze the problem, how can mechanical and thermal devices help to solve the problem
  • They Design or redesign mechanical as well as thermal devices by using analysis and computer-aided design.
  • Mechanical Engineer develops and test prototypes of devices they design.
  • They also examine the test results and can change the design if required.
  • Supervise the industrialized process for the device.

Top Companies Employing Mechanical Engineers

If you possess degree or diploma in mechanical engineering, you can easily find job in various government as well as private sector companies. Several government sector companies that employ mechanical engineers are as follows. You can also check Mechanical Engineering Salary In India from here

  • Indian Army
  • Indian Railways
  • Civil services
  • NTPC
  • CESC
  • ISRO
  • BHEL

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If, you have any doubt related to Mechanical Engineering Interview Questions & Answers PDF, Mechanical Engineering Technical Interview Questions then you are free to ask it in below given comment box. Our expert team will definitely solve your query about mechanical engineering interview questions pdf.

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