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Unformatted text preview: FNT #14: Heat, work and thermodynamics Damien Martin December 2, 2006 Question 1 Complete an activity, no solution as such. Question 2 Question 3 Here are three conditions: (I) Q = 0 (II) Δ U = 0 (III) W = 0 Consider the following processes applied to a fixed amount of ideal gas. Which of the following must hold for these types of processes. a) An isochronic (constant volume) process As W . = P V . any process at constant volume must mean V . = 0. Therefore W = 0, and so (I) is true. We know that we can heat a gas at constant volume, and this would be an example of Δ U = Q 6 = 0. Therefore the fact that the process occurs at constant V does not imply (II) or (III). b) An isobaric (constant pressure) process Here we have W = P Δ V . There is no requirement that Δ V = 0, so W 6 = 0 (generally). 1 Looking now at our ideal gas law: PV = nRT ⇒ P Δ V = nR Δ T (constant P ) If V increases (Δ V > 0) then T must also increase. This tells us that Δ U > as Δ U = Δ E thermal for an ideal gas. Therefore we can have processes withfor an ideal gas....
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 Summer '09
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 Thermodynamics, Energy, Entropy

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