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.