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Covers the study of (primarily homogeneous) macroscopic systems from a heat/energy/entropy point of view. Consider also using the tag: [statistical-mechanics].

7 votes
Accepted

What is the physical meaning of logarithm?

Lastly, since you ask about thermodynamics and the formula graven on Boltzmann's headstone, the logarithm is the grounding of the natural encoding of the idea that numbers of possibilities (volumes of …
Selene Routley's user avatar
1 vote

Heat balance: how to obtain $T(t)$ with energy in the form $u(T(t))$

Your question cannot be answered in its present form. The RHS is simply the heat flux out of the system, and that will be different depending on what your system is surrounded by and how those surroun …
Selene Routley's user avatar
1 vote
Accepted

What is the formula to find the temperature at a specific location of a material as a functi...

You'll need to read up on a little bit of mathematics to numerically solve problems like this. You need to solve the heat diffusion equation for the temperature $T(\vec{r},\,t)$ as a function of time …
Selene Routley's user avatar
1 vote

Nature of system taken in thermodynamics

See my answer to Why are the laws of thermodynamics “supreme among the laws of Nature”? for further discussion of these ideas. …
Selene Routley's user avatar
0 votes

Simplest way to analytically determine whether a claimed heat transfer process obeys the sec...

I think you should accept Nathaniel's answer, because the process you cite does indeed fulfill $\Delta\,S<0$, thus by the second law is impossible. Another way to show this (less general and elegant …
Selene Routley's user avatar
2 votes
Accepted

Converting speed distribution to frequency distribution

The Boltzmann distribution is the main and fundamental result you use here; see the Wikipedia article on the Microcanonical Ensemble. This is: $$p(E) = \frac{1}{\mathcal{Z}}\,g(E)\,\exp\left(-\frac{E …
Selene Routley's user avatar
1 vote

Why is entropy k times log of multiplicity?

Intuitively, this makes entropies add when we calculate the number of microstates for the combination of two systems: if the two systems are independent (uncorrelated), we simply multiply these number …
Selene Routley's user avatar
3 votes

Why cannot wood be fully burnt?

Wood is mostly cellulose, which burns to yield carbon dioxide and water, so this indeed can "burn fully". The rest - particulate matter in smoke and wood ash is made of minerals that the tree either d …
Selene Routley's user avatar
29 votes

Why are the laws of thermodynamics "supreme among the laws of Nature"?

Firstly, the laws of thermodynamics have very different origins and putative theoretical justifications and indeed the Eddington quote only talks about the second. … This, of course, is a "laboratory form" of the second law of thermodynamics. …
Selene Routley's user avatar
3 votes
Accepted

What determines how much energy a stone can hold?

You're problem is not fully defined, but let's begin to define it. Firstly, you're looking for something with a high emissivity $\epsilon$, so that it will absorb most of the incident light. This fa …
Selene Routley's user avatar
4 votes
Accepted

If black and white object are in isolated space will the black absorb heat from the white?

Maybe the following will help thinking about what is a really quite a complex question: it would be a fantastic last question for an undergrad thermodynamics exam BTW: You can abstract detail away by saying …
Selene Routley's user avatar
1 vote

Boltzmann constant--why units aren't joules per degree PER MOLECULE

Nature "does not forget" how it gets into a certain state, and a necessary condition for this to hold is that a system's information content cannot shrink, which of course is the second law of thermodynamics … and the wish to unite Shannon's information theory with Boltzmann / Gibbs thermodynamics. …
Selene Routley's user avatar
3 votes
Accepted

Explain entropy (again)

You're on the right track. Your statement can be true in special cases. More generally, the entropy is defined by the Boltzmann-headstone-equation you write down if $\Omega$ is the number of different …
Selene Routley's user avatar
2 votes

Spin version of Maxwell's demon: Where's the energy?

However, this system still complies with the second law of thermodynamics through Landauer's Principle. … One of the best references around on this stuff is Charles Bennett's review paper: Charles Bennett, "The Thermodynamics of Computation: A Review", Int. J. Theo. Phys., 21, No. 12, 1982 …
Selene Routley's user avatar
2 votes
Accepted

How does aerogel attain its enormous heat isolation properties?

Two ideas are especially to the heat isolation properties of aerogels: (i) aerogels are mostly gas and (ii) the Knudsen Effect. Clearly, heat isolation is achieved by blocking heat transfer paths: t …
Selene Routley's user avatar

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