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Presentation ON THERMODYNAMICS B.Sc.I , Paper II ( I Semester) By Dr. Mrs. Maheshmalkar P.R.

Presentation ON THERMODYNAMICS B.Sc.I , Paper II ( I Semester) By Dr. Mrs. Maheshmalkar P.R. THERMODYNAMICS Branch of science which deals with the processes involving heat and temperature inter conversion of heat and other forms of energy.

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Presentation ON THERMODYNAMICS B.Sc.I , Paper II ( I Semester) By Dr. Mrs. Maheshmalkar P.R.

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  1. Presentation ON THERMODYNAMICS B.Sc.I, Paper II ( I Semester) By Dr. Mrs. Maheshmalkar P.R.

  2. THERMODYNAMICS Branch of science which deals with the processes involving heat and temperature inter conversion of heat and other forms of energy.

  3. Thermodynamic State- Described by properties of the system e g P,V,T ,U called thermodynamic parameters • Equation Of State Is a relation between thermodynamic parameters • Sign convention- Heat gained by system is positive Work done by system is positive Increase in internal energy of system is positive • PV diagram- A graphical representation of the state of the system with help of two thermodynamic variables is called an indicator diagram. • Internal energy is simply the sum ofthe kinetic energies and potential energies ofthe molecules. The important thing about internal energy is that it depends only on the state of the system, not on how that state was achieved.

  4. Isothermal process-A process in which Temperature of the system remains constant though other variables may change. • Isobaric process-A process in which pressure of the system remains constant though other variables may change • Isochoric process-A process in which volume of the system remains constant though other variables may change. • Adiabatic process-A process in which no heat is exchanged is with the surroundings

  5. FIRST LAW OF THERMODYNAMICS-The general principle of conservation of • energy then implies that ΔQ = ΔU + ΔW . the energy (ΔQ) supplied to the system goes in partly to increase the internal energy of the system (ΔU) and the rest in work on the environment (ΔW). This is the First Law of Thermodynamics • If an amount of heat dQ is supplied to a system, a part of it may increase the internal energy by an amount dU while the remaining may be used as the external work done by the system. • dQ=dU + dW or • dQ=dU+ PdV

  6. The energy that can be extracted from a process can never be more than the energy put into the process • In other words • Energy out = Energy in • This is essentially the law of conservation of energy, i.e. • Energy can be neither created nor destroyed, it can only be converted from one form to another

  7. Isothermal process • Isothermal process-P,V may change but temperature is constant. • The cylinder must have conducting walls • It must happen very slowly so that heat produced during compression is absorbed by surroundings and heat lost during compression is supplied by surroundings. Work done in isothermal process • W=nRT ln(V2 /V1) • So if V2 >V1 then W>0 that is work is done by gas (isothermal expansion) • and if V1 >V2 then W<0 that is work is done on the gas (isothermal compression). Work done in isothermal process

  8. First law for isothermal process • For an ideal gas,internal energy depends only on temperature.Thus, there is no change in the internal energy of an ideal gas in an isothermal process. The First Law of Thermodynamics then implies that • heat supplied to the gas equals the work done by the gas : Q = W.

  9. Adiabatic processIn an adiabatic process, the system is insulated from the surroundings and heat absorbed or released is zero. Since there is no heat exchange with the surroundings, • When expansion happens temperature falls • When gas is compressed, temperature rises.

  10. Cyclic process Cyclic process- • In a cyclic process, the system returns to its • initial state. Since internal energy is a state • variable, ΔU = 0 for a cyclic process. The total heat absorbed equals the • work done by the system.

  11. HEAT ENGINES • Heat engine is a device by which a system is made to undergo a cyclic process that results in conversion of heat to work. • Components of a heat engine • 1 A working substance– For example, a mixture of fuel vapour and air in a gasoline or diesel engine or steam in a steam engine are the working substances. • 2 A hot reservoir or the source of heat • 3 A cold reservoir or the sink of heat • 4 mechanism for doing work Efficiency of heat engine • Efficiency is defined as external work obtained/heat energy absorbed by the source = W/Q1 • Or (Q1-Q2)/Q1 • Max value is 1 when Q2 =0

  12. Second Law Thermodynamics Kelvin-Planck statement- No process is possible whose sole result is the absorption of heat from a reservoir and complete conversion of the heat into work. Clausius statement No process is possible whose sole result is the transfer of heat from a colder object to a hotter object.

  13. THANK YOU

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