INTERVIEW QUESTIONS OF THERMODYNAMICS !!!

1.Why Entropy decreases with increase in temperature?

 Ans: ds=dQ/T. Entropy is inversely proportional to the temperature so, as temp. Increases, entropy decreases.

2.What is the difference between heat transfer and thermodynamics?
Ans: Heat transfer deals with the energy analysis which in transition and and depends on the modes of heat transfer like conduction, convection and radiation or combination of any modes. Heat transfer deals in non equilibrium domain and conditions while thermodynamics deals with study of system at equilibrium and does not depend on how heat transfer is calculated.

3.When a real gas behaves like ideal gas?

Ans:A real gas behaves like an ideal gas in low pressure and high temperature conditions.

4.What is Hess Law?

Ans:According to the Hess law the energy transfer is simply independent of the path being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

 5.What do you understand by latent heat? Give examples of latent      heat.

Ans:For pure substances, the heat effects accompanying changes in state at constant pressure (no temperature change being evident) are known as latent heats. Examples of latent heats are the heat of fusion, vaporization, sublimation and change in crystal form.

6.What is the difference between heat capacity and specific heat of the material?

Ans:The heat capacity of material is the amount of heat transformed to raise unit mass of a material 1° in temperature.

The specific heat of material is the ratio of the amount of heat transferred to raise unit mass of a material 1° in temperature to that required raise unit mass of water 1° of temperature at some specified temperature.

For most of the engineering purposes, heat capacities may be assumed numerically equal to specific heat values.

7.Why gas containers are mostly in a cylindrical shape?

Ans: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.

8.Explain why re-heater is used in gas turbine?

Ans:

The advantage of reheater is that it significantly increases the thrust; which is a prime reason for its use in gas turbines.

MANUAL VS AUTOMATIC TRANSMISSION : WHICH ONE IS BEST ??

Let us first understand what is manual and automatic transmission and then we can proceed with the comparison.

What is Manual Transmission ?

Manual transmission cars are the cars that allow the driver to change the gears as per driving needs and there is a manual clutch pedal used while changing gears. The clutch uses solid clutch plate and pressure plate mechanism.

What is Automatic Transmission ?

Automatic transmission on the other hand works automatically depending on the vehicle speed and engine speed. In automatic transmission cars, there is no clutch pedal, and clutch-plate mechanism is replaced with a hydraulic torque converter.

Manual Transmission:

• Initial cost of manual transmission cars is low.
• Fuel Efficiency of Manual transmission is higher because of low energy loss of a clutch plate based system.
• Preventive maintenance  cost for Manual transmission is slightly lower.
• Breakdown maintenance cost of  manual transmission car due to lesser complex systems.
• Manual transmission is usually more sporty compared to automatic transmission.
• Manual transmission is less comfortable in city conditions due to changing of gears in traffic.
• It requires more skills to drive a manual transmission car as there has to be a coordination between speed and gears.

Automatic Transmission:

• Initial cost of automatic transmission car is higher.
• Fuel Efficiency of Automatic transmission car is lower because of energy losses in hydraulic torque converter are higher.
• Preventive maintenance cost for automatic transmission car is slightly higher.
• Breakdown maintenance cost of  automatic transmission car is higher due to complex system.
• The driver does not have full liberty to choose what gears  he/she wants to drive in, thus it is less sporty as compared to the manual transmission.
• Automatic transmission is very comfortable as the driver needs not worry about the clutch and there is no need to manually change the gears with changing speeds. This adds a lots of convenience in city traffic.
• It requires lesser skills to drive an automatic transmission car compared to manual transmission car.

Basically, automatic transmissions are easier to use and more comfortable for the driver, while manual transmission vehicles are less expensive and more involved.

Comment in the section below,which is best according to you.

WHY CONCRETE NEED REINFORCEMENT ??

Reinforced concrete is mostly used for construction on a large scale due to its desirable mechanical properties. Reinforced concrete, or RCC, is concrete that contains embedded steel bars, plates, or fibers that strengthen the material.

Why concrete is reinforced??

Concrete can be very strong when it comes to absorbing stress in the form of compression. However, it does not perform well against tensile strength and crumbles when up against forces that tries to pull it apart. Concrete always experiences both kinds of stress in construction and if weight is put on the concrete beam from the top, it will hold up but deforms when it experiences tensile stress.

Reinforced materials are embedded in the concrete in such a way that the two materials resist the applied forces together.Concrete consists of a cement and stone aggregate mixture that forms a rigid structure with the addition of water. When steel that has a high tensile strength is embedded in concrete, the composite material withstands compression, bending, and tensile stresses. Such a material can be used for making any size and shape, for utilization in the construction.

The main quality of reinforced concrete is similarity of its coefficient of thermal expansion with that of steel, due to which the internal stresses initiated due to variation in thermal expansion or contraction are eliminated.

TOP FIVE RECENT DEVELOPMENT IN MECHANICAL ENGINEERING !!

1.)First turbine-powered street legal motorcycle -MTT Y2K SUPERBIKE

It’s the Most powerful production bike in the world which runs on diesel with kerosene. It has Rolls Royce-Allison gas turbine engine which produces 420 HP with 678 NM torque. 2-speed automatic transmission transfers excellent power, the top speed is more than 440 kph, weighs 230 kg. The design is great and fabricated from solid billets. It obtained Guinness World Record as the most expensive production motorcycle.

2.)Car engine - most powerful up to now 

The Devel Sixteen V16 Hyper-car - The custom made the real most powerful engine in the world is Devel Sixteen V16 Hyper-car which has 5000-hp, Quad-Turbo, 12.3-Liter V16. this is craziest power ever which has red-line of 8000 - hp. It is first revealed in Dubai Motor show, it reaches PS 0-60 in 1.8 seconds, and a top speed nearing 350 mph.

3.)Toyota launches first mass-market fuel cell car - Mirai, which converts hydrogen into electricity and emits nothing but water drops. It’s going to be the breakthrough in future for other vehicles like Forklifts, trucks, buses.

4.)Self driving Car

Google’s self driving car is almost driver less(manual assist needs in some dangerous turns) with start and stop option and which uses chauffeur system. The LIDAR(combined SONAR and RADAR) technology with Google map works in a precision manner. It uses 64 typical laser beams to find the objects around the car (360 degree). Cost of this system is around US $ 1 lakh. Accuracy, precision is more in this system which enables pre safe. Top speed is 40 kph.

5.)3D printing Technology

3D- printed steam turbine turbo-machinery used to convert Seawater into drinking water which was developed by GE.

Miniaturized Turbine used to compress and stream a mixture of air, salt and water through a hyper-cooling loop that freezes seawater. By freezing the mixture, the salt naturally separates in solid form, leaving just the ice. The ice is then melted, leaving clean water.

MULTIPLE CHOICE QUESTIONS ON ENGINE LUBRICATION SYSTEM !!

1-Lubricating oil

(A) Minimizes wear in moving parts

(B) Helps in keeping the parts cool

(C) Washes away and carries away dirt

(D) All of the above

(Ans: D)

2-Viscosity index (VI) is a measure for the change of viscosity with change in

(A) Temperature

(B) Pressure

(C) Volume

(D) All of the above

(Ans: A)

3-The following type of Lubrication system is used in two stroke engines

(A) Petroil (mist) system

(B) Wet sump system

(C) Dry sump system

(D) All of the above

(Ans: D)

4-In the following system, lubricating oil is carried in separate tanks from where it is fed to the engine

(A) Mist lubrication system

(B) Wet sump system

(C) Dry sump system

(D) Splash system

(Ans: C)

5-The following type of Lubrication system is used in Aircraft Engines

(A) Mist lubrication system

(B) Wet sump system

(C) Dry sump system

(D) Splash system

(Ans: C)

6-The following type(s) of Oil pump(s) is (are) used in Engine Lubrication system

(A) Gear type

(B) Rotor type

(C) Plunger type

(D) All of the above

(Ans: D)

7-The following is (are) oil pressure gauge(s)

(A) Pressure expansion type

(B) Electric type

(C) both (A) and (B)

(D) None of the above

(Ans: C)

8-The purpose of crankcase ventilation is to

(A) remove harmful particles from the engine

(B) provide proper lubrication to the engine

(C) provide air for combustion to the engine

(D) all of the above

(Ans: A)

9-The following part(s) is(are) lubricated by splash system

(A) Piston and piston rings

(B) Tappets

(C) Cams on camshaft

(D) All of the above

(Ans: D)

10-The following part is not lubricated by Pressure feed system

(A) Timing gears

(B) Valve rods and Push rods

(C) Rocker arms

(D)  Main bearings of crankshaft

(Ans: B)

INTERVIEW QUESTIONS OF PRODUCTION TECHNOLOGY !!

1) What do you mean by Smelting ?
 
Process of extraction of iron is called Smelting.

2) What do you understand by Specific Gravity and Tenacity ?

Specific Gravity . It is the ratio of the mass of 1cubic cm. of a substance to the mass of the same capacity of water.

• Tenacity .It is the property of metal due to which a metal becomes strong enough to resist the pulling force.

3) Define the following metal properties (a) Machinability (b)Malleability

(a) Machinability is the property of metal due to which a metal can easily be cut by cutting tools to obtain good surface finish. E.g.: Brass, Mild steel

• (b) Malleability is the property of the metal on account of which it can be extended in all directions by hammering or rolling. E.g.: Tin, Lead

4) Define Hardness of the metal ?

It is the property of the metal which makes a metal capable to resist surface penetration by other metals .Hard metals are High carbon steel and High speed steel.

5) What is the Toughness of metal ?

Toughness is the property of metal due to which without fracture a metal is able to withstand bending or torsion. Mild steel and wrought iron are tough metals.

6) Define the following properties of metal : (a) Fusibility (b) Stiffness (c) Ductility

Fusibility. It is the property of metal due to which a metal becomes fluid when it is heated.
Stiffness. It is the property of metal due to which a metal is capable of resisting deflection due to an externally applied load.
Ductility. It is the property of metal due to which a metal can be drawn into the form of wires without rupture.

7) Why are cast iron seasoned before machining ?

For easy machining and saving the cutting edge of the tool.

8) How does carbon affects the properties of steel ?

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.

9) Why are machine beds made of cast iron ?

Because it has more compressive strength and negligible shrinkage. It can easily cast into any integral shape, wear resisting and can absorb vibrations.

10) What is the difference between Wrought iron, Cast iron and Pig iron ?

Wrought iron contains less than 0.1% carbon and this is a product of puddling furnace. Cast iron is produced from cupola furnace. It contains 3­3.5% carbon in combined or free state. Pig iron is an iron carbon alloy contains 3­5% carbon along with impurities like manganese, sulphur and phosphorous. It is a product of blast furnace.

TIPS TO REMEMBER THERMODYNAMIC PROCESSES EXPLAINED !!

In thermodynamics you might get confused with various thermodynamic processes like isobaric, isochoric, isothermal, isetropic. This video explains various tricks to remember the meaning of various thermodynamic processes.