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Part -3 Most commonly asked Mechanical Interview Questions

Most commonly asked Mechanical Interview Questions with answer

1. What is the difference between Technology and Engineering?Ans. Engineering is application of science. Technology shows various methods of Engineering. A bridge can be made by using beams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is laws of force/load distribution.

2. How to Measure Temperature in Wet Bulb Thermometer?Ans. Wet bulb temperature is measured in a wet bulb thermometer by covering the bulb with a wick and wetting it with water. It corresponds to the dew point temperature and relative humidity.

3. What are the Advantages and Disadvantages of using LPG in Car?Ans. Advantages

1. Complete combustion
2. Fuel saving
3. Homogenous combustion

Disadvantages
1. As complete combustion is occurring ,more heat liberated,not advised for long journey, engine will be over heated
2. Installation is difficult
3. Reduce engine life efficiency
4. What is the difference between Speed and Economic Speed?Ans. The rated speed tells us about the maximum speed which can be achieved by a vehicle or some other machine but the economical speed means the speed limit at which the machine works efficiently with least consumption of fuel.eg-in normal bikes(not racing),the max.speed limit shown on speedometer is upto 120 kmph but companies always advice their customers to drive such bikes at around 60 kmph to have maximum mileage.

5. What is Powder Technology?Ans. Powder technology is one of the ways of making bearing material. In this method metals like bronze, Al, Fe are mixed and compressed to make an alloy.

6. State all the laws of Thermodynamics?Ans. There are three laws of the thermodynamics.
First Law: Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the total energy remains the same.
Second Law: When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but not in equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not decreased.
Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.

7. State the difference between Unilateral and Bilateral Tolerance?Ans. A unilateral tolerance is tolerance in which variation is permitted only in one direction from the specified direction.e.g. 1800 +0.000/-0.060 Bilateral tolerance is tolerance in which variation is permitted in both direction from the specified direction.e.g. 1800 +0.060/-0.060

8. What is the abbreviation of welding rod 7018?Ans. 7018 =
70=tensile strength 70000psi
1= welding position
8=current flux

9. What is difference between Welding and Brazing?Ans. In Welding concentrated heat (high temperature) is applied at the joint of metal and fuse together.
In Brazing involves significantly lower temperatures and does not entail the melting of base metals. Instead, a filler metal is melted and forced to flow into the joint through capillary action.
10. Which has more Efficiency Diesel Engine or Petrol Engine?Ans. Diesel engine has the better efficiency out of two.

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