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Chapter 12

Chapter 12. The Laws of Thermodynamics. Work in a Gas Cylinder. PV Diagrams. First Law of Thermodynamics. What is first law of thermodynamics? What does it do? What is the equation? How do I use it?. First Law – Signs. Signs of the terms in the equation Q

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Chapter 12

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  1. Chapter 12 The Laws of Thermodynamics

  2. Work in a Gas Cylinder

  3. PV Diagrams

  4. First Law of Thermodynamics • What is first law of thermodynamics? • What does it do? • What is the equation? • How do I use it?

  5. First Law – Signs • Signs of the terms in the equation • Q • Positive if energy is transferred to the system by heat • Negative if energy is transferred out of the system by heat • W • Positive if work is done on the system • Negative if work is done by the system • DU • Positive if the temperature increases • Negative if the temperature decreases

  6. Molar Specific Heat

  7. Degrees of Freedom

  8. Isolated System

  9. Second Law of Thermodynamics • What is the second law? • What does it do? • How do I use it?

  10. Types of Thermal Processes • Isobaric • Pressure stays constant • Horizontal line on the PV diagram • Isovolumetric • Volume stays constant • Vertical line on the PV diagram • Isothermal • Temperature stays the same • Adiabatic • No heat is exchanged with the surroundings

  11. Cyclic Processes

  12. Heat Engine

  13. Thermal Efficiency of a Heat Engine

  14. Heat Pumps and Refrigerators

  15. Reversible and Irreversible Processes

  16. Sadi Carnot • 1796 – 1832 • French Engineer • Founder of the science of thermodynamics • First to recognize the relationship between work and heat

  17. Carnot Cycle

  18. Example How much work is done by an ideal gas in expanding isothermally from an initial volume of 3 liters at 20 atm to a final volume of 24 liters?

  19. Example You have one and half hour before guest start arriving to your party when you suddenly realized that you forgot to buy ice for your drinks. You quickly put 1.0 L of water at 10 degree Celsius into your ice cube tray and pop them into the freezer. Will you have ice for your guest. The label on your refrigerator states that COP=5.5 and power rating 550W. Assume that only 10% of power contributes to freezing water.

  20. Example Find the efficiency of an Otto cycle shown in the figure and express the answer in terms of the ratio R=Va/Vb.

  21. Entropy • What is entropy?

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