T H E R M O D Y N A M I C S
(1) Explain briefly what you understand about Microscopic and Macroscopic approaches to study Thermodynamics.
ANSWER: There are two approaches to study thermodynamic problem. They are known as
Where as when we analyse a system by its gross or time averaged effects of molecules we say the approach is macroscopic. Here matter is assumed to be continuous not discrete. It is regarded as a continuum, just like a physical field is taken as continuum.
(ii) As no. of molecules are very large hence its not possible to study individual molecules, hence the analysis in microscopic approach is done by statistical methods with the help of the theory of probability and the concept is known as Statistical Mechanics.
Where as in macroscopic approach the analysis is done on the basis classical or Newtonian Mechanics.
(iii) In Microscopic approach Statistical Mechanics and different probability distribution theories like Maxwell's velocity distribution theory have been employed.
Where as in Macroscopic approach is based on classical mechanics and calculus.
(iv) In Microscopic approach the value of the system parameters are indirectly calculated as most of them cant be directly measured.
Where as in macroscopic approach most of properties are not only measurable but also sensible too.
(2) What do you understand by the term Temperature? What is Thermal Equilibrium?
Here I want to write my view points about the term "equilibrium" with it's precise definition as an physical real events.
We all know that although we comprehend matter as a continuous distribution of masses that means that we can take infinitesimally and arbitrarily small volume of mass, but in reality, matter is composed of tiny particles called molecules. These molecules in gases are almost free of intermolecular forces, and always move randomly which is named as Brownian Motion. Gas molecules posses kinetic energy, so whenever they collide with the wall of the container within which the gas has been kept. Every collision is responsible for the momentum transfer to the wall which the wall resisted due to it's elastic properties. The change in momentum produces a thrust to the wall and we call it the pressure of the gas which means total force per unit surface area of the wall of the container. So, gross kinetic energy of the molecules due to their random Brownian motion has two effects on the wall of the container, one is due to the thrust on the wall named as Pressure of the enclosed gas. And the average Kinetic Energy of a molecules is the basis of stored energy of the gas molecules and we perceive it as temperature.
When a body at certain temperature, T1 is kept in contact with another body having a different temperature T2, it means that there exists a difference in average kinetic energy of the molecules between the bodies.
(3) Explain the term Thermodynamic Equilibrium. Explain the conditions of Thermodynamic Equilibrium. Also explain the conditions of Thermodynamic Equilibrium. (5)
Ans: Equilibrium is a state or condition of a system, when there is no change in the value of properties with respect to time. In equilibrium condition, there exists no driving force inside the system and absence of driving force ensures that there is no change in the properties of the system. Basically, changes occur due to the existence of either (a) a temperature gradient, (b) a pressure gradient or (c) chemical potential in the system or between system and surroundings.
Based on these equilibrium conditions are of three types.
(ii) Mechanical Equilibrium: If there doesn't exist any pressure difference between a system and its surroundings, then the system is in Mechanical Equilibrium and it tells that there will not be any work interactions between a system and its surroundings.
(iii) Chemical Equilibrium: If in a system that contains multi-components working fluid/substance and if there is not any chemical potential between them, then there will not be any chemical reaction inside a system and this condition is called as chemical equilibrium.
When a system is in thermal, mechanical and chemical equilibrium, then the system is called is in Thermodynamic equilibrium.
(4) Explain the statements of Second law of thermodynamics.
Answer: Kelvin Planck and Clausius statements of the second law of Thermodynamics.
The second law of thermodynamics can also be stated using Clausius, Kelvin and Planck statements also. Each statement is based on an irreversible process. The Clausius and the Kelvin and Planck statements of the second law of Thermodynamics are given below:
Clausius statement:
Clausius statement states “it is impossible for a self acting machine working in a cyclic process without any external force, to transfer heat from a body at a lower temperature to a body at a higher temperature. It considers transformation of heat between two heat reservoirs.
Kelvin – Planck statement:
Kelvin – Planck statement states “it is impossible to construct an engine, which is operating in a cycle produces no other effect except to external heat from a single reservoir and do equivalent amount of work.
It considers the transformation of heat into work.
Equivalence of Clausius statement to the Kelvin – Planck statement
Consider a reservoir having temperature T1 and another reservoir at temperature T2. The temperature T1 is higher than the temperature T2. Consider a heat pump which requires no work and transfers an amount of Q2 from low temperature to a higher temperature reservoir, which is violating the Clausius statement. Consider an amount of heat Q1 (greater than Q2) be transferred from higher temperature reservoir to a heat engine which develops a net work, W = Q1 – Q2 and rejects Q2 to the low temperature reservoir.
Since there is no heat interaction with the low temperature, it can be eliminated. The combined system of the heat engine and heat pump acts then like a heat engine exchanging heat with a single reservoir, which violates the Kelvin – Planck statement.
(5) Explain the concepts of continuum with the help of density.explain whether we can term density as an intensive properties of the system,justify your answer.
Ans: "Continuum" is a concept.
(6)What is a thermodynamic process? Explain the differences between reversible and irreversible process? What are the common causes of irreversibility.
(7)"....heat and work done are actually different forms of energy...and we termed them as energy in transition..." justify the statement.
(8) Discuss the importance of zeroth law. discuss its role in temperature measurement
(9) What is internal energy? Prove that internal energy is a property of the system.
(10) What is the difference between flow work and pdV or displacement work. Also explain the term enthalpy.
(11) Classify thermodynamic system with example.discuss each of them briefly.
(12) What is SSSF energy equation? explain it and derive the equation.
First Law of Thermodynamics:
Statement: When a closed system executes a complete cycle the sum of heat interactions is equal to the sum of work interactions.
Mathematically, ΣQ=Σ W
The summations being over the entire cycle.
(1) Explain briefly what you understand about Microscopic and Macroscopic approaches to study Thermodynamics.
or
Differentiate between them. Also state which approaches is considered in studying Engineering thermodynamics. ANSWER: There are two approaches to study thermodynamic problem. They are known as
- (i) Microscopic approach and
- (ii) Macroscopic approach.
Where as when we analyse a system by its gross or time averaged effects of molecules we say the approach is macroscopic. Here matter is assumed to be continuous not discrete. It is regarded as a continuum, just like a physical field is taken as continuum.
(ii) As no. of molecules are very large hence its not possible to study individual molecules, hence the analysis in microscopic approach is done by statistical methods with the help of the theory of probability and the concept is known as Statistical Mechanics.
Where as in macroscopic approach the analysis is done on the basis classical or Newtonian Mechanics.
(iii) In Microscopic approach Statistical Mechanics and different probability distribution theories like Maxwell's velocity distribution theory have been employed.
Where as in Macroscopic approach is based on classical mechanics and calculus.
(iv) In Microscopic approach the value of the system parameters are indirectly calculated as most of them cant be directly measured.
Where as in macroscopic approach most of properties are not only measurable but also sensible too.
(2) What do you understand by the term Temperature? What is Thermal Equilibrium?
Here I want to write my view points about the term "equilibrium" with it's precise definition as an physical real events.
We all know that although we comprehend matter as a continuous distribution of masses that means that we can take infinitesimally and arbitrarily small volume of mass, but in reality, matter is composed of tiny particles called molecules. These molecules in gases are almost free of intermolecular forces, and always move randomly which is named as Brownian Motion. Gas molecules posses kinetic energy, so whenever they collide with the wall of the container within which the gas has been kept. Every collision is responsible for the momentum transfer to the wall which the wall resisted due to it's elastic properties. The change in momentum produces a thrust to the wall and we call it the pressure of the gas which means total force per unit surface area of the wall of the container. So, gross kinetic energy of the molecules due to their random Brownian motion has two effects on the wall of the container, one is due to the thrust on the wall named as Pressure of the enclosed gas. And the average Kinetic Energy of a molecules is the basis of stored energy of the gas molecules and we perceive it as temperature.
When a body at certain temperature, T1 is kept in contact with another body having a different temperature T2, it means that there exists a difference in average kinetic energy of the molecules between the bodies.
(3) Explain the term Thermodynamic Equilibrium. Explain the conditions of Thermodynamic Equilibrium. Also explain the conditions of Thermodynamic Equilibrium. (5)
Ans: Equilibrium is a state or condition of a system, when there is no change in the value of properties with respect to time. In equilibrium condition, there exists no driving force inside the system and absence of driving force ensures that there is no change in the properties of the system. Basically, changes occur due to the existence of either (a) a temperature gradient, (b) a pressure gradient or (c) chemical potential in the system or between system and surroundings.
Based on these equilibrium conditions are of three types.
- Thermal Equilibrium
- Mechanical Equilibrium
- Chemical Equilibrium
(ii) Mechanical Equilibrium: If there doesn't exist any pressure difference between a system and its surroundings, then the system is in Mechanical Equilibrium and it tells that there will not be any work interactions between a system and its surroundings.
(iii) Chemical Equilibrium: If in a system that contains multi-components working fluid/substance and if there is not any chemical potential between them, then there will not be any chemical reaction inside a system and this condition is called as chemical equilibrium.
When a system is in thermal, mechanical and chemical equilibrium, then the system is called is in Thermodynamic equilibrium.
(4) Explain the statements of Second law of thermodynamics.
Answer: Kelvin Planck and Clausius statements of the second law of Thermodynamics.
The second law of thermodynamics can also be stated using Clausius, Kelvin and Planck statements also. Each statement is based on an irreversible process. The Clausius and the Kelvin and Planck statements of the second law of Thermodynamics are given below:
Clausius statement:
Clausius statement states “it is impossible for a self acting machine working in a cyclic process without any external force, to transfer heat from a body at a lower temperature to a body at a higher temperature. It considers transformation of heat between two heat reservoirs.
Kelvin – Planck statement:
Kelvin – Planck statement states “it is impossible to construct an engine, which is operating in a cycle produces no other effect except to external heat from a single reservoir and do equivalent amount of work.
It considers the transformation of heat into work.
Equivalence of Clausius statement to the Kelvin – Planck statement
Consider a reservoir having temperature T1 and another reservoir at temperature T2. The temperature T1 is higher than the temperature T2. Consider a heat pump which requires no work and transfers an amount of Q2 from low temperature to a higher temperature reservoir, which is violating the Clausius statement. Consider an amount of heat Q1 (greater than Q2) be transferred from higher temperature reservoir to a heat engine which develops a net work, W = Q1 – Q2 and rejects Q2 to the low temperature reservoir.
Since there is no heat interaction with the low temperature, it can be eliminated. The combined system of the heat engine and heat pump acts then like a heat engine exchanging heat with a single reservoir, which violates the Kelvin – Planck statement.
(5) Explain the concepts of continuum with the help of density.explain whether we can term density as an intensive properties of the system,justify your answer.
Ans: "Continuum" is a concept.
(6)What is a thermodynamic process? Explain the differences between reversible and irreversible process? What are the common causes of irreversibility.
(7)"....heat and work done are actually different forms of energy...and we termed them as energy in transition..." justify the statement.
or
Compare Heat Transfer with Work transfer...also explain why they are termed as path function? Differentiate between path and point function of a thermodynamic system. (8) Discuss the importance of zeroth law. discuss its role in temperature measurement
(9) What is internal energy? Prove that internal energy is a property of the system.
(10) What is the difference between flow work and pdV or displacement work. Also explain the term enthalpy.
(11) Classify thermodynamic system with example.discuss each of them briefly.
(12) What is SSSF energy equation? explain it and derive the equation.
First Law of Thermodynamics:
Statement: When a closed system executes a complete cycle the sum of heat interactions is equal to the sum of work interactions.
Mathematically, ΣQ=Σ W
The summations being over the entire cycle.
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