Lecture_25

# Lecture_25 - happens to T, P, V) What sign does W have?...

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Thermodynamics

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Thermodynamics How do heat and other forms of energy exchange between systems. What are the limits? Objects are no microscopically identical but have the same macroscopic properties (P, V, N, T). Interactions between systems (forces, energy transfer) can be described by work done by one on the other or heat flow between them.
0 th Law Review: If two systems are both in thermal equilibrium with a third system, then they are in thermal equilibrium with each other

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1 st Law If some heat, Q, flows into a system, the system does some work, W, on its environment, then the internal energy of the system changes by Δ U = U f U i = Q W Thermodynamic process
Positive or Negative? Example: Consider a balloon for which W = Q. What can we say about the thermodynamic process (e.g. What can we say about what

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Unformatted text preview: happens to T, P, V) What sign does W have? Calculating Work We can plot P-V diagrams. The area under the curve is W. W = F Δ x F = PA W = P ( A Δ x )= P Δ V Fixed Quantities Fixed Quantities W = n RT ln ( V f V i ) Fixed Quantities P ∝ 1 V γ Δ U =− W Example: Here W>0. What can we say about T? The Path Makes a Difference Reversibility Reversible: When a process is reversed, the final state (of the system and the environment) is exactly the same as the initial state. Irreversible: There is no way to return the system and its environment to the original state 2 nd Law Heat flows spontaneously from a warm body to a colder one. It is not possible for heat to flow spontaneously from a cold body to a warmer one....
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## This note was uploaded on 12/07/2011 for the course PHYS 220 taught by Professor Chang during the Fall '09 term at Purdue University.

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Lecture_25 - happens to T, P, V) What sign does W have?...

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