Top 50 Mechanical Interview Questions You Must Prepare 24.Jun.2024

Q1. In Order To Increase Efficiency And Reduce Co Emissions And Other Emissions, Clear Coal Technologies Are Receiving Major Attention. What Are These ?

  1. Advanced pulverised and pressurised pulverised fuel combustion.
  2. Atmospheric fluidised bed combustion and pressurised fluidised bed combustion.
  3. Supercritical boilers.
  4. Integrated gasification combined cycle systems.
  5. Advanced integrated gasification, including fuel cell systems.
  6. Magneto hydrodynamic electricity generation.

Q2. What Does Following Alloy Designation Indicate Fg 250 ?

Grey cast iron with tensile strength of 250 MPa.

Q3. What Are The Losses In A Centrifugal Pump ?

The losses in a centrifugal pump are : Friction losses due to eddies in flow, leakage, friction loss due to rotation of impeller in chamber of water, gland and bearing power losses.

Q4. What Are The Main Factors That Are Responsible For The Formation Of Built Up Edge ?

The main factors that are responsible for the formation of built up edge are :

  1. Extreme pressure in the cutting zone
  2. High friction in the tool chip interface
  3. High local temperature.

Q5. How Does The Head Change In Pipe Flow With Change In Diameter, If Capacity Is Constant?

At constant capacity, head is proportional to

Q6. What Is The Difference Between Geometric, Kinematic, And Dynamic Similarities Between Model And Prototype ?


Geometric similarity is mainly for same shape for model and prototype, kinematic similarity is concerned with streamline pattern, whereas dynamic similarity concerns the ratio of forces.

Q7. What Is The Difference Between Firm Power And Secondary Power In Hydro Power Plants ?

The approximate constant and continuous power which is assured at power station and would be available throughout the year is called firm power.

In run-of-the river schemes which are generally designed for % availability of water, the firm power would be available for at least % of the years during the life of the scheme. However in some years discharge in the river may be more than % availability discharge and some extra power known as secondary power can be generated.

Q8. 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.

Q9. Which Refrigerant Is Used For Ice Plant And Trport Refrigeration ?

Ammonia and CO2 respectively.

Q10. What Is Metacentre ?

Metacentre is the point at the intersection of the buoyancy with the vertical axis of the body.

Q11. Why Steam Is In Open Space And Water Inside Tube In Condensers Used In Power Plants ?

Overall heat trfer coefficient can be increased by increasing velocity of water in tube. Further steam needs more space due to higher specific volume.

Q12. 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.

Q13. 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.

Q14. Briefly Explain The Advantages Of Cycloidal And Involute Gears?

The advantages of the Cycloidal gears are as follows:

  • Having a wider flank as compared to Involute gears they are considered to have more strength and hence can withstand further load and stress.
  • The contact in case of cycloidal gears is between the concave surface and the convex flank. This results in less wear and tear.
  • No interference occurs in these types of gears.

The advantages of Involute gears are as follows:

  • The primary advantage of involute gears is that it allows the changing of the centre distance of a pair without changing the velocity ratio.
  • The pressure angle remains constant from start to end teeth, this results in less wear and smooth running of the gears.
  • The involute gears are easier to manufacture as they can be generated in a single curve ( the face and flank ).

Q15. On What Factors The Efficiency Of Pump Depends ?

Efficiency of a pump (centrifugal) depends on the size, speed, and proportions of the impeller and casing.

Q16. 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.

Q17. List Two Effects Of Manganese In Plain Carbon Steels?

Manganese increases tensile strength and hardness. It decreases weldability.

Q18. What Is Capillarity And When Liquid Rises Or Falls ?

Capillarity : The rise or fall of a liquid in a capillary tube caused by surface tension. The magnitude of rise or fall depends on the relative magnitudes of the cohesion of the liquid and adhesion of the liquid to the walls of the containing vessels. Capillarity is of importance in tubes smaller than 10 mm diameter.

Rise of liquid : Liquids rise (in capillary tube) when they wet and adhesion of the liquid to the walls is greater than the cohesion of the liquid.

Fall of liquid : Liquids fall (in capillary tube) when they do not wet and the cohesion of the liquid is greater than the adhesion of the liquid to the walls.

Q19. We Often Come Across Use Of Jet Pumps In Process Industry ? What Is The Reason For This ?

Jet pumps are easy to maintain and can be used to trport gases, liquids and mixtures of both.

Q20. Which Reactor Uses Heavy Water As Moderator ?


Q21. Which Parameter Remains Constant In A Throttling Process ?


Q22. What Are The Harmful Effects Of Sulphur In Coal Used For Power Generation ?

Sulphur in coal gives rise to number of ecological problems ranging from acid mine drainage to ash waste problems and air pollution due to SO2 emission. Emission of S02 is the cause of acid rain and is responsible for severe environmental damage.

Q23. In Which Type Of Motion, Acceleration Is Directly Proportional To Displacement ?


Q24. What Are The Factors To Be Considered While Evaluating The Machinability ?

  1. Tool life
  2. Rate of metal removal
  3. Power required
  4. Surface texture and size of component
  5. Temperature of tool (or) chip.

Q25. On What Basis Can Sliding Contact Bearings Be Classified? Explain?

Sliding contact bearings can be classified on the basis of the thickness of the lubricating agent layer between the bearing and the journal. They can be classified as follows:

  • Thick film bearings: These type of bearings have their working surface separated by a layer of the lubricant. They are also known as hydrodynamic lubricated bearings.
  • Thin film bearings: In this type of bearings the surfaces are partially in direct contact with each other even after the presence of a lubricant. The other name for such type of bearings is boundary lubricated bearings.
  • Zero Film Bearings: These type of bearings as their name suggests have no lubricant present between the contact layers.
  • Externally or hydrostatically pressurized lubricated bearings: These bearings are able to without any relative motion support steady loads.

Q26. What Is The Necessary And Sufficient Condition For Bodies In Floatation To Be In Stable Equilibrium ?

Centre of gravity of body should be located below metacentre.

Q27. Explain The Difference Between Energy Line And Hydraulic Grade Line ?

The energy line is a graphical representation of the energy at each section.

Hydraulic grade line lies below the energy line by an amount equal to the velocity head at the section.

Q28. For Which Type Of Flow The Velocity Distribution In A Pipe Is Parabolic?

For uniform laminar flow.

Q29. What Are The Different Types Of Springs And Explain Them Briefly?

Springs can be broadly classified into the following types:

  • Helical Springs: These springs as their name suggests are in coil form and are in the shape of helix. The primary purpose of such springs are to handle compressive and tensile loads. They can be further classified into two types: compression helical spring and tension helical spring each having their own unique areas of application./
  • Conical and volute springs: Both these spring types have specialized areas of usage where springs with adaptable rate according to the load is required. In case of conical springs they are wound so as to have a uniform pitch while on the other hand volute springs are wound in a slight manner of a paraboloid.
  • Torsion Springs: The characteristics of such springs is that they tend to wind up by the load. They can be either helical or spiral in shape. These types of springs are used in circuit breaker mechanisms.
  • Leaf springs: These types of springs are comprised of metal plates of different lengths held together with the help of bolts and clamps. Commonly seen being used as suspensions for vehicles.
  • Disc Springs: As the name suggests such types of springs are comprised of conical discs held together by a bolt or tube.
  • Special Purpose Springs: These springs are all together made of different materials such as air and water.

Q30. What Are The Three Functions Served By A Surge Tank In A Hydro Plant ?

The three functions served by a surge tank are

  1. flow regulation - act as a reservoir for acceptance or delivery of water to meet requirements of load changes.
  2. water-hammer relief or pressure regulation.
  3. improvement in speed regulation.


Q31. What Is Vapour Pressure And When It Becomes Important ?

Vapour pressure is the partial pressure created by the vapour molecules when evaporation takes place within an enclosed space. It becomes important when negative pressures are involved.

Q32. Explain The Difference Between Horizontal And Vertical Components Of Hydrostatic Force ?

The horizontal component of the hydrostatic force on any surface is equal to the normal force on the vertical projection of the surface and acts through the center of pressure for the vertical projection.

Vertical component of the hydrostatic force on any surface is equal to the weight of the volume of liquid above the area and passes through the e.g. of the volume.

Q33. What Do You Mean By Drill Sleeve And A Drill Socket ?

The drill sleeve is suitable for holding only one size of shank. If the taper shank of the tool is smaller than the taper in the spindle hole, a taper sleeve is used.

When the taper tool shank is larger than the spindle taper, drill sockets are used to hold the tools. Drill sockets are much longer in size than the drill sleeves.

Q34. Whether Bernoulli's Equation Is Applicable For Streamline Straight And Rotational Flows ?


Q35. How The Characteristics Of Fuel Like Front End Volatility, Mid-range Volatility And Tail End Volatility Affect S.i. Engines ?

These characteristics affect SI engines in cold starting, icing of carburettor and dilution in crankcase respectively.

Q36. Explain What You Understand By The Term Hydrostatic Paradox ?

Hydrostatic paradox is the phenomenon that the floor load of water in vessels of different shapes carrying water at same level depends only on the area of the bottom surface and not on the shape of the vessel.

Q37. Explain The Difference Between Rotational And Irrotational Flow?

In rotational flow the vorticity is non zero and in irrotational flow it is zero. In irrotational flow the net rotation of a fluid element about its own mass centre is zero as it moves from one place to another. For it, dv/dx = du/dy.

Q38. What Is The Name Given To Combined Process Of Cooling And Humidifying ?

Evaporative Cooling.

Q39. No.,, Reduction In Gas Turbines Is Challenge To Meet Environmental Regulations. What Measures Are Taken In This Regard ?

NO* in gas turbines is controlled by

  1. injecting water/steam into combustor,
  2. using selective catalytic redaction (SCR) and non-catalytic reduction system (NRS), and
  3. better combustor design.

Q40. What Are Thermal Neutrons ?

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

Q41. Which Element Is Added In Steel To Increase Resistance To Corrosion ?


Q42. What Is The Criterion For Determining Economic Diameter Of Power Tunnel ?

The economic diameter of a power tunnel is determined such that the total value of following two factors is least

  1. annual loss of revenue on account of power head lost due to friction.
  2. recurring annual expenditure.

Q43. In Which Type Of Flow The Stream Lines, Streak Lines And Path Lines Are Identical ?

In steady flow.

Q44. Name Pressure Compounded And Velocity Compounded Turbine?

Rateau and Curtis respectively.

Q45. Under What Condition The Thickness Of Thermal Boundary Layer And Hydrodynamic Boundary Layer Is Same ?

When Prandtl number is equal to unity.

Q46. What Is Factor Of Evaporation ?

It is the ratio of heat change from feed water to steam and the heat of vaporization of steam at atmospheric pressure.

Q47. Why Belts Are Subject To Creep ?

Due to uneven extension and contraction of belt.

Q48. Describe Briefly The Different Cold Drawing Processes?

Some of the important cold drawing processes are as follows:

  • Bar and Rod Drawing: In the case of bar drawing the hot drawn bars are at first pickled, washed and coated to prevent oxidation. Once this is done a draw bench is used for the process of cold drawing. In order to make an end possible to enter a drawing die the diameter of the rod is reduced by the swaging operation. This end is fastened by chains to the draw bench and the end is gripped by the jaws of the carriage. In this method a high surface finish and accuracy dimensionally is obtained. The products of this process can be used directly without any further machining.
  • Wire Drawing: Similar to the above process the bars are first pickled, washed and coated to prevent any oxidation. After this the rods are passed through several dies of decreasing diameter to provide a desired reduction in the size ( diameter ). The dies used for the reduction process is generally made up of carbide materials.
  • Tube Drawing: This type of drawing is very similar to the bar drawing process and in majority of cases it is accomplished by the use of a draw bench.

Q49. When Maximum Discharge Is Obtained In Nozzle ?

At the critical pressure ratio.

Q50. Which Elements Increase The Corrosion Resistance Of Steel ?

Chromium and nickel.