1. Physics 52 - Heat and Optics Dr. Joseph F. Becker Physics Department San Jose State University © 2005 J. F. Becker

2. Chapter 17 Temperature and Heat THERMODYNAMICS © 2005 J. F. Becker San Jose State University Physics 52 Heat and Optics

3. Thermometers are used to measure temperature – a measure of hotness and coldness. (a) A system whose temperature is specified by the value of the length L. (b) A system whose temperature is specified by the value of the pressure p.

4. The Zeroeth Law of Thermodynamics. (a) If systems A and B are each in thermal equilibrium with system C, then (b) A and B are in thermal equilibrium with each other. Blue = insulation, red = conducting material.

5. (a) A bimetallic strip bends when heated because one metal (red) expands more than the other. (b) A bimetallic strip, usually in the form of a spiral, may be used as a thermometer.

6. Graph of absolute pressure versus temperature for a constant-volume low-density gas thermometer. p V = n R T = N k T

7. Relations among Kelvin, Celsius, and Fahrenheit temperature scales.

8. We can visualize forces between neighboring atoms by imagining them to be connected by springs that are easier to stretch than to compress. Graph of potential energy versus distance between neighboring atoms shows that the forces are not symmetrical.

9. The volume of one gram of water in the temperature range from 0 o C to 10 o C. By 100 o C the volume will have increased to 1.034 cm 3. If the coefficient of volume expansion were constant the curve would be straight.

10. The same temperature change of the same system may be accomplished by: (a) doing work on it or (b) adding heat to it. work heat

11. Specific heat capacity of water as a function of temperature. The value of c varies by less than 1% between 0 o C and 100 o C.

12. Temperature versus time for water initially in the solid phase (ice). Heat is added at a constant rate. Phase change: Q = +/- m L

13. Steady-state heat flow due to conduction in a uniform rod.

14. Conduction of heat. We can approximate heat flow through the walls of a picnic cooler by heat flow through a single flat slab of Styrofoam.

15. Heat flow along two metal bars, one of steel and one of copper, connected end- to-end in SERIES. H total = H Cu = H Steel

16. Heat flow along two metal bars, one of steel and one of copper, connected end- to-end in PARALLEL. H total = H Cu + H Steel

17. A long rod is in perfect thermal contact with boiling water at one end and an ice- water mixture at the other end. Find H = ? and L 2 = ? H = dQ / dt = k A ( T H - T C ) / L 100 o C0oC0oC Area = 4.00 cm 2

18. Water has higher specific heat than land. CONVECTION

19. Convection in a thunder storm. Hot, moist air is less dense that cool, dry air and hence is lifted by buoyancy.

20. Electric water heater to supply a continuous supply of hot water. Water 0.500 kg/min T H = ? = 120 Volts = 15 Amp.

21. Review