2014-09-18

basics of thermodynamics-part-3

What is meant by thermodynamic equilibrium?
When a system is in thermodynamic equilibrium, it should satisfy the following three conditions.
(a) Mechanical Equilibrium :- Pressure remains constant
(b) Thermal equilibrium :- Temperature remains constant
(c) Chemical equilibrium : There is no chemical reaction.

What do you understand by pure substance?
A pure substance is defined as one that is homogeneous and invariable in chemical composition throughout its mass.

What is the difference between a heat pump and a refrigerator?
Heat pump is a device which operating in cyclic process, maintains the temperature of a hot body at a temperature higher than the temperature of surroundings.

A refrigerator is a device which operating in a cyclic process, maintains the temperature of a cold body at a temperature lower than the temperature of the surroundings.

What is the characteristic gas equation?
 Characteristic gas equation is pV = mRT
Where,
                p = pressure
                V = Volume
                R = Characteristic gas constant
                T = Temperature.

What do you mean by quasi-static process?
Infinite slowness is the characteristic feature of a quasi-static process. A quasi-static process is that a succession of equilibrium states. A quasi-static process is also called as reversible process.

State the law of conservation of energy and give a mathematical equation for it. Mention also examples to support this law.
Energy can neither be created nor destroyed although it may be transformed from one form to another. Mathematical form of the law is

DE = q + w

In the running of an electric motor, electrical energy is converted into mechanical energy.

Why does the amount of entropy in the universe always increase?
The second law of thermodynamics states the entropy in the universe always increases:  some energy is always lost as heat, and heat is a disordered form of energy.

What is meant by steady flow process?
During the process the rate of flow of mass and energy across the boundary remains constant, is known as steady flow process.

What is the difference between steady flow and non – flow process?
During the steady flow process the rate of flow of mass and energy across the boundary remains constant.
In case of non – flow across the system and boundary.

What are the processes involved in Carnot cycle.
Carnot cycle consist of
           i) Reversible isothermal compression
           ii) Isentropic compression
           iii) Reversible isothermal expansion
           iv) Isentropic expansion