176-final-exam-review

176-final-exam-review - Physics 176 Topics to Review For...

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Physics 176 Topics to Review For the Final Exam Professor Henry Greenside May 2, 2011 Thermodynamic Concepts and Facts 1. Practical criteria for identifying when a macroscopic system is in thermodynamic equilibrium: all macroscopic features are time independence, temperature same everywhere, pressure same everywhere unless there is an external spatially varying field, chemical potential same everywhere, properties independent of history, and no relative macroscopic motion (only rigid rotation and translation of the macroscopic system allowed). 2. Concept of a relaxation time τ , especially thermal, diffusive, and mechanical relaxation times. Know the fact that τ L 2 where L is some characteristic size of the system, and understand how the L 2 scaling is connected to a random walk arising from collisions. 3. The concepts of thermal energy U , heat Q and work W for some macroscopic equilibrium system, and that they are related by the first law of thermodynamics, Δ U = Q + W . Make sure you understand how the signs of Q and W are chosen. 4. The concept of a state variable such as energy, volume, entropy, temperature, and chemical potential. However, heat and work are not state variables. 5. The concept of an equation of state that relates various state variables ( PV = NkT is an example). While most equations of state are discovered experimentally and known empirically, they can sometimes be discovered by calculating the pressure P in terms of some thermodynamic potential, e.g., P = - ( ∂F/∂V ) T,N , which in turn lets one compute P in terms of a partition function. 6. The concepts of intensive and extensive thermodynamic variables. 7. The definition and applications of heat capacity and specific heats, especially that C V = ( ∂U/∂T ) V and C P = ( ∂H/∂T P where H = U + PV is the enthalpy. One therefore has C P = C V + P ( ∂V/∂T ) P . 8. Detailed quantitative knowledge of the experimental heat capacities C ( T ) of a solid, of a gas of identical diatomic molecules, and of a paramagnet as a function of temperature. 9. The concepts of quasistatic, reversible, and irreversible thermodynamic processes. 10. The concept of a quasistatic adiabatic process, which is also a constant-entropy process. 11. How to calculate changes in entropy: via Δ S = Q/T for a constant temperature process (phase transition or reservoir) and via integrals R C ( T ) /T dT over temperature ranges involving a known heat capacity C ( T ). 12. The thermodynamic definition of temperature 1 /T = ( ∂S/∂U ) N,V in terms of the entropy. From a given equation of state S = S ( U,V,N ), how to derive the temperature T of the system, the energy dependence U ( T ) and so the heat capacity C = C ( T ). 13. How to calculate the changes in energy, heat, work, temperature, and entropy for an arbitrary process of
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This note was uploaded on 10/20/2011 for the course PHYSICS 176 taught by Professor Behringer during the Spring '08 term at Duke.

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176-final-exam-review - Physics 176 Topics to Review For...

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