HIS 322m - The Law of Conservation of Energy (First Law of...

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The Law of Conservation of Energy (First Law of Thermodynamics) total  amount of energy in a closed system is a constant Energy cannot be created or destroyed; can be transferred through  work to other forms  Sadi Carnot (French, 1796-1832) analyzed the workings of steam engines  in his 1824 Reflections of the Motive Power of Heat.  Saw need for both hot and  cold; used idea of caloric flowing in Carnot Cycle to find maximum efficiency James Joule (English, 1818-1889): ‘paddlewheel experiment’ (1847)  measured conversion of work into heat in a set ratio; ‘mechanical equivalent of  heat.’  Heat seen as a form of energy. First lay of thermodynamics: energy can  neither be created or destroyed If total energy is conserved, why can’t we get it all;  In 1850s, Rudolf  Clausius (German, 1822-1888) and William Thomson (Lord Kelvin, Scottish,  1824-1907) formulated broad empirical principle: Left to itself, heat flows from hot  cold; ‘lukewarmness; or entropy increases, and the energy available to us for use  decreases.  Second Law of Thermodynamics says the world is running down  toward an inevitable ‘heat death’ As the lukewarmness increases, the average heat increases   Science discovers, technology applies; can go other direction: scientists  try to explain what technology is already doing
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The Mechanical Program and the Kinetic Theory of Gases 2 April 2008 The gas laws: pressure, volume, and temperature P1(V2)=K(T1) P2(V2)=K(T2) Before people believed in the Caloric Model of gas: Gas particle inside, caloric atmosphere around: When squeezed, the gas particle is released, creating heat. If heat isn’t ‘caloric,’ what is it? And why does it tend to flow from hot to cold? According to kinetic theory, gases consist of particles bouncing around at high speeds. In 1857, Rudolf Clausius said the temperature of a gas could be identified with the average kinetic energy of its particles, and its total heat with the sum of the kinetic energies of all of its particles. Why does smell takes so long to travel across a room if they move at the speed of light? B/C they molecules are bouncing around and hitting things and each other. In 1860s, James Clerk Maxwell (Scottish, 1831–1879) extended this by applying statistical concepts borrowed from social sciences: temperature, pressure, etc.,were stable averages resulting from the random motions of huge numbers of particles. Heat flow, and thus increase in entropy, result from particle speeds averaging out through collisions. T2>T1 (picture of two waves T1 and T2: #of molecules on y axis and speed of molecules
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This note was uploaded on 04/28/2008 for the course HIS 322m taught by Professor Hunt during the Spring '08 term at University of Texas at Dallas, Richardson.

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HIS 322m - The Law of Conservation of Energy (First Law of...

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