371 reputation
113
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location Brisbane
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visits member for 3 years, 2 months
seen Dec 16 at 0:59

I'm an undergraduate Engineering/Mathematics Student down in Brisbane, Australia. Interested in learning as much as I possibly can about maths, particularly the ideas/constructions/history/motivation behind the classic undergraduate concepts.


Nov
8
awarded  Tumbleweed
Nov
1
answered Exact Relation between voltage and current
Nov
1
asked Callen's Second Postulate - Composite or Closed+Composite systems?
Oct
23
asked Two Limits in Thermodynamics - Reducing Driving Force and Increasing Resistance
Oct
14
awarded  Popular Question
Oct
14
awarded  Nice Question
Oct
14
comment How did Kelvin make this fascinating calculation?
Thanks, that's beautiful in the terribly-obvious-when-you-see-it kind of way :)
Oct
14
accepted How did Kelvin make this fascinating calculation?
Oct
13
asked How did Kelvin make this fascinating calculation?
Oct
9
asked Is every imaginable quasi-static locus (with non-decreasing entropy) physically realisable?
Sep
24
awarded  Autobiographer
Sep
18
comment Inconsistency between Helmholtz and Gibbs Free Energies
This is probably a terribly silly question, but if two phases are at equilibrium at constant $p, T$ and $N$, doesn't that mean that they have equal Gibbs free energy (per mole), so that irrespective of the fraction of ice or water, the Gibbs free energy is the same single value?
Sep
18
accepted Inconsistency between Helmholtz and Gibbs Free Energies
Sep
18
comment Inconsistency between Helmholtz and Gibbs Free Energies
I can imagine that being a problem. Thanks for your help: I've only skimmed through Chapter 8 of Callen, but it's probably time to study it in a bit more depth :)
Sep
18
comment Inconsistency between Helmholtz and Gibbs Free Energies
OK, I think I'm seeing where you're coming from. Concavity of $A(V)$ would certainly solve the problem, as then both $P(V)$ and $V(P)$ would be single-valued and we'd all be happy. I was under the impression though that they need not always both be single-valued - sometimes at a certain pressure the volume could be multiple-valued - say at a phase transition with liquid and gas co-existing. Ahh, but that would just be at one single value of $P$, wouldn't it? That would be the discrete jump of $V(P)$ you mention. At that discrete jump then in some sense $V(P)$ is multi-valued, but only there.
Sep
18
comment Inconsistency between Helmholtz and Gibbs Free Energies
Thanks for your answer :) Just to clarify, are you saying that $G$ need not be a single-valued function of $p, N$ and $T$, as I'd assumed? I was under the impression that the whole point of making the Legendre transformation was to change coordinate systems, so that we find a new 'thermodynamic potential' $G$ with the same minimization properties as the internal energy, but which is a (presumably single-valued) function of the intensive variables. Thanks
Sep
13
asked Inconsistency between Helmholtz and Gibbs Free Energies
Sep
6
comment Generalisation of Reversible Equation to Non-Reversible Situations Because it Only Contains 'Properties of the System'
I asked this question years ago, and your response is exactly what I'd say to my younger self today :) The only thing I dislike is the use of the word 'reversible' - I prefer quasi-static, and reserve reversible for quasi static isentropic processes, in line with callen's thermodynamics text.
Aug
29
awarded  Popular Question
Aug
12
accepted Why doesn't Euler's theorem provide an *absolute* energy scale