Lect07 - Physics 213! ! Sept. 14, 2006 Physics 213! ! Sept....

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today 2nd Law of Thermodynamics (see last lecture’s notes) Entropy Electric charge and the structure of matter Conductors and insulators Induced charges Physics 213 Sept. 14, 2006 7.1 … and a note on heat pumps Consider T in ~ 68° F and T out ~ 41° F: K Carnot = T H /(T H -T C ) = 293K/15K ~ 20 K Actual ~ 4 Method: Natural Gas Furnace Electric Heat Heat Pump Heating Efficiency or COP 90% 100% K~4 Fuel used per 1000 J of Heat 1kJ/0.9=1110J Electricity used per 1000 J of Heat 20 J 1000 J 1000 J/4=250 J Electric Power Plant Efficiency 0.4 0.4 0.4 Energy used to make Electricity 20 J/0.4=50 J 1000 J/ 0.4=2500 J 250 J/0.4=625 J Energy resources wasted 110J +30J=140J 1500 J 375 J What is consumed, What you pay $ for 1160 J 2500 J 625 J Physics 213 Sept. 14, 2006 7.2 Entropy: • quantitative measure of disorder • a state variable A gas increases its disorder if it expands (V ! V +dV.
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This note was uploaded on 05/25/2008 for the course PHYS 2213 taught by Professor Perelstein,m during the Spring '07 term at Cornell University (Engineering School).

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Lect07 - Physics 213! ! Sept. 14, 2006 Physics 213! ! Sept....

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