PHY101_Chap12Fall09

# PHY101_Chap12Fall09 - Chapter 12 The Laws of Thermodynamics...

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12.1 Work in Thermodynamic Processes Dealing with a gas Assumed to be in thermodynamic equilibrium Every part of the gas is at the same temperature Every part of the gas is at the same pressure Ideal gas law applies Chapter 12 The Laws of Thermodynamics

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Work Done by a System W > 0 if Δ V > 0 expanding system does positive work W < 0 if Δ V < 0 contracting system does negative work W = 0 if Δ V = 0 system with constant volume does no work •For visualization, P-V diagrams are used to describe a thermal process. Doesn’t have to be P-V, but we have the best feel for it M M Δ y W = F d = PAd = P Δ V
If work done by a system results in increased volume, then The work done is 1.Positive 2.Negative 3.Zero 4.Not enough information Quiz Qn.1

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P-V diagram V P 1 2 V 1 V 2 P
Area on a P-V diagram has units associated with: 1.energy. 2.momentum. 3.temperature. 4.change in temperature. Quiz Qn. 2

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Example : Find the work done in (a) and (b)
12.2 The First Law of Thermodynamics Δ U = Q - W Heat flow into the system Change in internal energy of the system Work done by the system Equivalent ways of writing 1st law: Q = Δ U + W Nothing more than energy conservation Three key quantities: internal energy, heat into the system, work done by the system First law

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Quiz Qn. 3
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## This note was uploaded on 01/02/2010 for the course PHY 101 taught by Professor Pralle during the Fall '08 term at SUNY Buffalo.

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PHY101_Chap12Fall09 - Chapter 12 The Laws of Thermodynamics...

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