lecture26

# lecture26 - Phys 2101 Gabriela Gonzlez pV=nRT If volume is...

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Phys 2101 Gabriela González

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2 If volume is constant (“isochoric” process), W=0, and Tp -1 is constant. If temperature is constant (“isothermal” process), Δ E int =0, and pV is constant. If pressure is constant (“isobaric” process), W, Q, and Δ E in are not zero, but TV -1 is constant. Adiabatic processes happen when Q = 0: the system is thermally insulated, or because the process happens very quickly. Temperature, pressure and volume all change, but the quantities pV γ and T V γ -1 are constant, where γ = C P /C V (=4/3=1.67 for monoatomic gases) The curve in a pV diagram is called an “adiabat” pV=nRT
3 One liter of gas with γ = 1.3 is at 292 K and 1.4 atm pressure. It is suddenly compressed (adiabatically) to half its original volume. Find its final pressure and temperature. Adiabatic process: pV γ and T V γ -1 are constant: p 2 = p 1 (V 1 /V 2 ) γ = 1.4 atm 2 1.3 = 3.4 atm T 2 = T 1 (V 1 /V 2 ) γ - 1 = 292K 2 0.3 = 359 K The gas is now cooled back to 292 K at constant pressure. What is its final volume? Constant pressure: p= nRT/V , or T/V, is constant V 3 =V 2 (T 3 /T 2 ) = 0.5 l (292 K/ 359 K) = 0.41 l

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4 One mole of an ideal diatomic gas undergoes a transition from a to c along the diagonal path in the figure. The temperature of the gas at point
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## This note was uploaded on 12/01/2011 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.

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lecture26 - Phys 2101 Gabriela Gonzlez pV=nRT If volume is...

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