lec 4 - Work Interactions Heat Interactions Mechanics...

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Unformatted text preview: Work Interactions, Heat Interactions Mechanics definition of work: ∫ ⋅ = 2 1 s s s d F W r r Examples: 1. Constant force field, e.g. earth’s gravity g m F = = W 2. A spring x k F = = W 3. Friction (dry) mg F μ = = W Thermodynamic definition of Work Interaction: A work interaction between system and environment is one where the sole resulting effect could have been the raising or lowering of a weight. Sign convention: > W work done by the system (positive) < W work done on the system (negative) Work is not a Property of the system—No single measurement can tell you how much work was done on or by the system. Thermodynamic work is based on the path the system takes between beginning and end states. As a result, Work is described by an inexact differential: ∫ = 2 1 W W δ Changes in parameters are described by exact differentials: An important example of a work interaction used to approximate thermodynamic processes is pressure - volume (compression - expansion) work....
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lec 4 - Work Interactions Heat Interactions Mechanics...

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