1. Temperature Physics 313 Professor Lee Carkner Lecture 2

2. Thermodynamics  Thermodynamics is the study of energy   e.g. a cylinder of gas accelerated to high speed has an increased kinetic energy but the same temperature  We will discuss the properties of a system and how they relate to internal energy, through both the macroscopic and microscopic points of view 

3. Macroscopic Microscopic   Specify a few basic bulk properties   Classical Thermodynamics   Specify states of individual units   Statistical mechanics

4. Systems  Material separated from its surroundings by a boundary   Closed   e.g. gas in a piston  Open   e.g. an automobile radiator

5. Processes  State   Process   Quasi - Static (Quasi-Equilibrium) Process   slow changes  Non-quasi static processes are discontinuous

6. Equilibrium  Define two properties for a system   If the two properties remain constant the system is in equilibrium  A system is in equilibrium with itself if its properties are constant throughout the whole system 

7. System Boundaries  Adiabatic Wall   thermal insulator  Dithermal wall   thermal conductor

9. Temperature Proxies  Changes in temperature cause changes in other system properties   Two consequences:  We measure T by measuring changes in other properties    If T is not constant, nothing else is   Often given at standard temperature (0 C) or room temperature (20 C)

10. Thermal Expansion  The degree to which a linear distance varies with temperature is given by:   Change in one dimension (linear expansion)   Very small (~one part in a million per degree) in most cases   Note that  itself is temperature dependant

11. Typical “toothed” bridge expansion joint

12. “Rocker” support that allows deck expansion

13. “Sleeved” railing expansion section

14. The Brooklyn Bridge

15.  Built:  Designed: John A Roebling  Chief Engineer: Washington A. Roebling  Height:  Length:  World’s longest suspension bridge until 1903  To learn more about the Brooklyn Bridge visit your local library:  The Great Bridge : The Epic Story of the Building of the Brooklyn Bridge by David McCullough

16. Brooklyn Bridge cables

17. Stringing the Cables

18. Main Cable

19. Thermal Equilibrium  Two systems separated by a dithermal wall that do not change properties    If the two systems are not in thermal equilibrium they will exchange heat until they are 

20. Zeroth Law  Three systems A, B and T  A and T --  B and T --  Then for A and B   Two systems in thermal equilibrium with a third are in thermal equilibrium with each other

22. Isotherms  Plot pressure and volume   Curve is called an isotherm   Temperature determines thermal equilibrium

24. Temperature  Take an object T and mark it so that changes in its properties can be measured   Calibrate the measurements so that your scale corresponds to universally accepted situations   e.g. mercury thermometer

25. Temperature Scales  Gabriel Daniel Fahrenheit invented the mercury thermometer in 1714   32 F is freezing point of water, 212 is chosen for boiling point (32+180)  Anders Celsius introduced his scale in 1742   William Thomson, Lord Kelvin, developed the absolute (Kelvin) scale from his analysis of ideal engines 

26. Temperatures  Universe (Planck time) ~  Universe (today) ~  Average star ~  Average dust cloud ~  Planet (Mercury) ~  Planet (Neptune) ~  Planet (habitable) ~