BASICS OF THERMODYNAMICS Vikasana - Bridge Course 2012 1
Energy: 1. Energy is an abstract physical quantity 2. It can be measured only by means of its effect Vikasana - Bridge Course 2012 2
HEAT Heat is a form of energy Vikasana - Bridge Course 2012 3
Effects of Heat: 1. Expansion 2. Rise in temperature 3. Work done Vikasana - Bridge Course 2012 4
Work done: According to the law of mechanics, energy is measured by amount of work done Vikasana - Bridge Course 2012 5
Thermodynamics: Macroscopic science it deals with bulk system Branch of physics deals with inter conversion of heat into other form of energy (work) Vikasana - Bridge Course 2012 6
Examples: 1. When water in a container starts t boiling, plate covering the container starts moving up and down. 2. Rub your hands one against the another for few second you will feel that your hands are wormed. Vikasana - Bridge Course 2012 7
Mechanical work of rubbing hands is converted in to heat Vikasana - Bridge Course 2012 8
Conclusion: It is possible to convert work in to heat or heat in to work. Vikasana - Bridge Course 2012 9
LORD Kelvin Named the process as Thermodynamics Vikasana - Bridge Course 2012 10
In Latin thermodynamics means Motion of Heat Vikasana - Bridge Course 2012 11
Basic terms required to understand thermodynamics Vikasana - Bridge Course 2012 12
1. Closed system: There is no mass transferred between the system and the surroundings. Vikasana - Bridge Course 2012 13
02. Open system: There will be both matter and energy transfer across the boundary of the system. Vikasana - Bridge Course 2012 14
03. Isolated system: There is neither matter nor energy transfer across the boundary of the system. Vikasana - Bridge Course 2012 15
04. Thermodynamic system: A certain amount of matter under investigation. Vikasana - Bridge Course 2012 16
05. Surroundings: A given thermodynamic system interacts with all other matter outside the system. The matter outside the system is called the surrounding. Vikasana - Bridge Course 2012 17
Thermodynamic Variables OR Thermodynamic co-ordinates, ordinates, measurable quantities such as i) )p pressure ii) volume and iii) temperature are called thermodynamic variables. Vikasana - Bridge Course 2012 18
Mechanical Equilibrium: There should be no unbalanced forces between the various parts of the systems or between the system and the surrounding Vikasana - Bridge Course 2012 19
Thermal Equilibrium: The temperature of every part of the system must be same as that t of surroundings *A *B *C *D T A = T C = T B = T D Vikasana - Bridge Course 2012 20
Chemical Equilibrium: Chemical composition of the system stand remain fixed and definite. Vikasana - Bridge Course 2012 21
Thermodynamic Equilibrium: A thermodynamic system is said to be in complete equilibrium, it is in mechanical, thermal and chemical equilibrium. Vikasana - Bridge Course 2012 22
Equation of State: t The equation relating the thermodynamic co-ordinates ordinates is called the equation of state. Ex:- PV = RT represents the equation of state for a perfect gas Vikasana - Bridge Course 2012 23
Thermodynamic process: Taking the thermodynamic system form one thermodynamic state to another thermodynamic state. Ex:- Compression or Expansion of gas Vikasana - Bridge Course 2012 24
Internal Energy: Every system (solid, liquid or gas) possess two types of energy. 1. Potential Energy (PE) 2. Kinetic Energy (KE) Vikasana - Bridge Course 2012 25
* Kinetic Energy is due to motion of molecules l with in the system. * Potential Energy is due to molecular configurations of the molecules. Total energy of the system (E) = PE + KE Vikasana - Bridge Course 2012 26
Internal energy of the Real gas depends on volume and temperature. Vikasana - Bridge Course 2012 27
When temperature of the gas is increased, the molecules move rapidly and randomly, there by increasing the K.E Vikasana - Bridge Course 2012 28
Increasing the KE in turn increases the internal energy of the gas Vikasana - Bridge Course 2012 29
Internal energy can be taken as a measure of temperature. Vikasana - Bridge Course 2012 30
In thermodynamics there are three laws: 1. Zeroth Law of thermodynamics 2. First Law of thermodynamics, and 3. Second Law of thermodynamics Vikasana - Bridge Course 2012 31
Zeroth Law of Thermodynamics: R.H Flower formulated this law in 1931, By that time I Law and II Law had already been formulated. Hence this law is called Zeroth Law. It is more basic Vikasana - Bridge Course 2012 32
Zeroth Law of Thermodynamics Statement:- If a two system A and B are separately in thermal equilibrium with third system C, then A and B are in thermal equilibrium with each other. Vikasana - Bridge Course 2012 33
Explanation:- If T A = T C then A and C are in equilibrium. Similarly if T B = T c then B and C are in equilibrium. According to zeroth law A and B are in thermal equilibrium with each other if T A = T C and T B = T C, then T A = T B AT A CT C T B T B Vikasana - Bridge Course 2012 34
Significance of zeroth Law: zeroth law gives a measurable quantity to decide whether two systems are in equilibrium or not. Vikasana - Bridge Course 2012 35
First Law of Thermodynamics Statement:- Heat energy given to a system is equal to the sum of the increase in internal energy and the external workdone by the system. Vikasana - Bridge Course 2012 36
Explanation: dq = du + dw du change in internal energy dw work done dq Heat energy given to a system Vikasana - Bridge Course 2012 37
Sign convension: * When heat is given to a system dq is taken as +ve. * If the heat is drawn from the system dq is taken as ve. Vikasana - Bridge Course 2012 38
Phase diagram: A graphical representation of variation of pressure (P) and temperature (T) at constant volume (V). Vikasana - Bridge Course 2012 39
Indicator diagram (P-V diagram): The graphical representation of variation of Pressure with the Volume of the system is called P-V diagram or Indicator diagram Vikasana - Bridge Course 2012 40
p-v diagram or Indicator diagram y-axis A(p 1 v 1 ) p B(p 2 v 2 ) v x-axis Vikasana - Bridge Course 2012 41
Indicator diagram help us to determine work done by the gas or on the gas during thermodynamic process Vikasana - Bridge Course 2012 42
Applications of first law of Thermodynamics Vikasana - Bridge Course 2012 43
1. Isothermal process: It is a thermodynamic process that takes place at constant temperature dq = du + dw du = 0 dq = dw Ex: Ice is converted into water at 0 C Vikasana - Bridge Course 2012 44
2. Adiabatic process: Heat can neither enters the system nor leaves the system dq = 0 du = - dw. Ex: Bursting of cycle tyre. Vikasana - Bridge Course 2012 45
3. Isobaric process: The thermodynamic process that takes place at constant pressure none of the quantities du, dw and dq is zero. Ex: 1) Heating water in atmospheric pressure. 2) Conversion of ice into water. Vikasana - Bridge Course 2012 46
4. Isochoric process: The thermodynamic process that t takes place at constant volume dw = 0 dq = du + p.dv dq = du Ex: When ice melts, the change in volume is negligeble. Vikasana - Bridge Course 2012 47
Reversible process: The process that t can be retraced in the reverse direction, so that all the changes occurring in the direct process are reversed. Ex:- 1. Evaporation of water 2. Condensation of vapour 3. Ice changing into water. Vikasana - Bridge Course 2012 48
Irreversible process: The process that cannot be retraced back in the reverse direction. Ex:- 1. Sudden expansion of gas 2. Heat produced by friction Vikasana - Bridge Course 2012 49