Chapter19 - Chapter 19 Demos:

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PHYS141, S09 Chapter 19 1 Chapter 19 Demos: http://www.physics.umd.edu/deptinfo/facilities/lecdem/lecdem.htm I1-13 – Thermal expansion – bimetal strip I4-31 – ice bomb I1-11 thermal expansion – ball and hole I6-01 gas pressure – model I4-01 pvt phase diagrams for c02 and h20 I2-22: thermodynamics by touch I2-27: thermal equilibrium between aluminum and copper I3-52: constant volume gas thermometer Cup of hot coffee Standard thermometer Thanks to Prof LaPorta and “Peer Instruction” by Eric Mazur
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Thermodynamics PHYS141, S09 Chapter 19 2 Beginnings of a field that, at its more advanced level, is called statistical physics. So far, we have considered point objects, rigid objects, or objects with only a few permitted internal motions. We will now study the behavior of large groups of independent (although simple) objects. Development of this field was simultaneous with the development of machines, power plants, steam engines, etc (1850’s) Will study things like: • How to control/changes a material’s temperature • What happens when objects of different temperature are put into contact • How changes in temperature affect materials • temperature, conservation of energy and work • a microscopic understanding of these phenomena • the laws of thermodynamics and heat engines • Entropy
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Temperature PHYS141, S09 Chapter 19 3 In Statistical mechanics, see that the internal energy (kinetic and potential) stored in an object is related to the object’s temperature and to the “number of internal degrees of freedom” (ways of storing energy) the material possesses. E int = n deg rees 2 N molecules k B T
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PHYS141, S09 Chapter 19 4 When two objects are placed in contact, they will exchange energy until they come to a common, stable temperature. They are then said to be in thermal equilibrium. heat: energy exchanged between two objects because of a difference in temperature. When a very “large” object (we’ll see more precisely what we mean by large later) is placed in contact with a very small object, the heat lost/gained by the large object to the small will have a negligible effect on its temperature. Some objects have properties that depend on their temperature. We’ll put them in contact with some object whose temperature we want to know and use them as a thermometer. I2-27: thermal equilibrium between Al and Cu
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Chapter19 - Chapter 19 Demos:

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