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I am an engineer learning physics in my spare time. My current focus is quantum field theory and the Standard Model.


Oct
21
comment Why can we say that $\bar{d}Q=TdS$?
In non-equilibrium thermodynamics, one common assumption is that of local thermodynamic equilibrium, where each infinitesimal cell in the medium is assumed to be approximated by an equilibrium state, even though there is no equilibrium at the larger scale. The addition of Onsager relations then allows for a description of how those local states interact and evolve.
Oct
21
comment Why can we say that $\bar{d}Q=TdS$?
This equation is one form of the fundemental thermodynamic equation. It is valid between equilibrium states. That is because quantities such as $U$ or $T$ are not well defined for non-equilibrium states, since there is no statistical ensemble associated with those states. However, it is often possible to have quasi-equilibrium states that are closely approximated by equilibrium states for which thoese quantities are well defined. This is why those thermodynamic relations can be broadly applied.
Oct
21
comment Why can we say that $\bar{d}Q=TdS$?
Statistical physics usually deals with static systems. Non-equilibrium thermodynamics is the branch that explores those issues further.
Oct
21
answered Compute convective heat transfer coefficient for a condensing steam
Oct
21
answered Why can we say that $\bar{d}Q=TdS$?
Oct
21
awarded  Popular Question
Sep
24
awarded  Autobiographer
Aug
24
comment Is Fourier's law of conduction a consequence of the second principle?
@Nikos: Would you have a reference textbook to suggest for me to explore this question?
Aug
21
accepted Is Fourier's law of conduction a consequence of the second principle?
Aug
21
comment Is Fourier's law of conduction a consequence of the second principle?
I find it suprising that we need to have two independent laws that imply that heat moves from hot to cold, in a non-reversible way. What would be the minimum additional assumption that would allow derivation of Fourier's law?
Aug
21
asked Is Fourier's law of conduction a consequence of the second principle?
Aug
13
answered What is the effect of an increase in pressure on latent heat of vaporization?
Aug
8
comment Why should mass be attractive in nature?
Isn't it provable that spin 2 particles like the graviton generate attractive forces between object of similar charge?
Aug
7
comment Stability of the hydrogen atom and positronium
Perhaps I should have said 'simple' process rather : tree-level or one loop order. Positronium annihilation is straightforward to write using simple Feynman diagrams, But I was not able to write one for quark and electron, and I was wondering if one reason was the lack of interaction vertex between up quark (charge +2/3) and electron (-1).
Aug
6
accepted Stability of the hydrogen atom and positronium
Aug
6
asked Stability of the hydrogen atom and positronium
Aug
5
accepted Why did the Homestake experiment only detect solar neutrinos?
Aug
5
asked Why did the Homestake experiment only detect solar neutrinos?
Aug
5
comment Why do liquids boil when their vapor pressure equals the ambient pressure?
Perhaps I should rephrase that. What I meant to say is that the bubbles that can be observed before the water is hot enough for boiling are composed of dissolved air gases.
Aug
5
answered Why do liquids boil when their vapor pressure equals the ambient pressure?