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Hello guys, there is not much awareness about how your peers crack an interview, although mostly it depends upon an individual’s mindset. Recruiters create a labyrinth in which you have to carefully yet confidently and smartly take a step one at a time. What I mean is- they try to test your basic skills and personal skills and try to grasp an idea about your technical knowledge, Strength, and Weakness. Sometimes, these questions are straight forward but there may be times when they twist the statement which has the same sense as a straight question would have. In this blog, I have mentioned a few questions to see how a technical interview goes about.

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1. Explain the second law of thermodynamics.
Ans:

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

2. What Is Knurling?
Ans:
Knurling is a machining process normally carried out 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.

3. Is It The Stress That, Produces Strain Or Strain Produces Stress?
Ans:
A Force applied to an object will cause a displacement. Strain is effectively a measure of this displacement (change in length divided by the 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.

4. How Are The Pneumatic System And The Hydraulic System Similar?
Ans:
Pneumatics use gases such as air or nitrogen, hydraulics use oil or water, both systems use pressure to act on a specific application.

5. What Is The Role Of Nitrogen In Welding?
Ans:

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.

6. How Can You Convert Air Mass To Air Volume?
Ans:

Mass = density * volume.
Air density is p/RT, where R is the gas constant for air (287 J/kg-K), T is the absolute temperature, and p is the pressure, equal to 101325 Pa at sea level.
At sea level and room temperature, the density of air is rho 101325 N/m2/ (287 N-m/ (kg-K)*293 K or about a) 2 kg/mc)

7. What are the differences between pneumatics and hydraulics?
Ans:

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

8. What are the advantages of gear drive?
Ans:

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 compared 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.

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9. Which conducts heat faster steel copper or brass?
Ans:

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.

10. Why The Plastic Materials Used In The Screwdriver’s Handles?
Ans:

Due to non-conducting nature of plastic, it is widely used for electricity purposes. Moreover, plastic is cheap and strong so it is less prone to damage. Furthermore, plastic does not bend and does not slips from the users hands.

11. What Is Octane Number And Cetane Number?
Ans:

Octane number can be defined as a percentage, by volume, of iso-octane in the mixture of iso-octane and h-heptane. It is the measure of rating of SI engine.
While cetane number can be defined as a 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.

12. What is gear ratio?
Ans:

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

13. What is annealing?

Ans:
It is a process of heating a material above the recrystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

14. What are the advantages of gear drive?
Ans:

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 compared 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.

15. Why gas containers are mostly cylindrical in shape?
Ans:

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.

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16. What is the difference between scavenging and supercharging?
Ans:

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

17. What is Hess’s law?
Ans:
According to the Hess law, the energy transfer is simply independent of the way being followed. If the reactant and the product of the whole process are the same then the same amount of energy will be dissipated or absorbed.

18. Explain the difference between a pipe and a tube.
Ans:

A pipe is measured based on its inner diameter (ID) whereas a tube is measured based on the outer diameter (OD). Other than the dimensions there is no major difference between the two.

19. Explain why the diesel engine is known as a high torque and petrol engine as a high-speed engine?
Ans:

Each power stroke in a petrol engine releases more heat and is converted into mechanical energy due to a higher rate of burning. This is the reason the petrol engine has higher power and acceleration.
A diesel engine is a compression ignition engine with a higher compression ratio, therefore extreme pressure is high. Since the piston of a diesel engine is larger, more torque is delivered in produced.

20. Explain the difference between projectile motion and rocket motion.
Ans:

The major difference is that a projectile has no motor or a rocket on it, due to which the momentum is given to it as it is launched. A pen thrown across a room is a classic example of projectile motion. On the other hand, a rocket or missile has a motor on it which helps in accelerating while moving. This helps in resisting other forces such as gravity. A projectile does not have any specific shape, it is a point mass, whereas the rocket has a particular shape having its center of gravity situated at a particular point on its body. Thus rocket motion comes under kinetics and projectile comes under kinematics.

21. How does carbon affect the properties of steel?
Ans:

If carbon content is higher the degree of hardness is more and the melting point is lower, If carbon percentage is lower it is easy to forging and forge welding.

22. Why heat treatment of steel is necessary ?
Ans:

● To improve machinability.
● To obtain desired properties.
● To increase resistance of corrosion.
● To change electrical and magnetic properties.
● To relieve the stresses after cold or hot working.
● To refine the grain size.

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23. What is meant by gear ratio?
Ans:

A gear ratio is a direct measure of ratio of the rotational speeds of two or more interlocking gears.

24. What is Case hardening ?
Ans:
It is a process of making outer surfaces harder of the steel part. Generally it is done for the following purposes,
● To make outer surface harder.
● To bring the cost cheaper
● To utilize low carbon steel.

25. Why is it not possible to harden unalloyed tool steel part right through its full thickness ?
Ans:
Because it requires very high cooling rate which is only possible for its outer surface.
26. Differentiate between hardening and tempering ?
The main purpose of hardening is to resist wear and enable it to cut the other metals and reheating is not necessary. The main purpose of tempering is to reduce some of hardness and to increase the toughness. It consists of reheating after hardening to a temperature below the critical range.
27. What are the different alloying elements and their effects on the properties of the steel ?
● Cobalt: It gives excellent magnetic property and improves the cutting quality of the steel.
● Chromium: It gives greater hardness and resists corrosion and forging.
● Molybdenum: It gives greater hardness and resistance to drawing and forging.
● Nickel: It lifts the tensile strength, improves wearing property and protects from corrosion.
● Tungsten: It gives fine grain structure, greater hardness and cutting toughness.
● Vanadium: It gives cutting toughness resistance to wear and tear and greater hardness.

28. What is Soldering ?
Ans:

It is a process of joining two or more metal pieces by using solder.

29. What is the material of shaper tool ?
Ans:

Generally used HSS(High Speed Steel),sometimes satellite, carbide tipped tools may also be used.
30. Why gas containers are mostly in a cylindrical shape?
The ideal shape would be a sphere. The container must have the capacity to withstand the extremely high pressure of liquefied gas. A spherical shape helps in distributing these forces uniformly.
So, as we saw above, these are some of the many questions and queries done to take a clear analysis about you. I am eager to hear from you any request about any field. I invite questions and will come back with an answer.

Author-

Komal Gurnani
CAD Department
Seven Mentor Pvt. Ltd

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