Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Maybe combine with [tag:statistical-mechanics].

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Proving that the Boltzmann entropy is equal to the thermodynamic entropy

I've been trying to understand how we can equate the Boltzmann entropy $k_B \ln \Omega$ and the entropy from thermodynamics. I'm following the approach found in the first chapter in Pathria's ...
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1answer
13 views

Why does a soda bottle foam or froth when dropped? [duplicate]

Secondly, if I do drop a soda bottle how long do I have to keep it for it to return to its original state or condition, I.e. safe to open without froth spraying everywhere; or is there some rule of ...
3
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1answer
44 views

What is the temperature of water at the end of the pipe?

I need to solve the following problem for a practical application. Water, initially at temperature $T_0$, flows with a constant speed $v$ through a PVC tube of length $l$ and diameter $D$. The ...
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1answer
48 views

Which temperature does $T$ in Clausius inequality ($\oint \frac{\delta Q}T\le 0$) refer to?

I got a little confused about the temperature in Clausius inequality. As you can see in this answer of Luboš Motl, it seems that temperature is the temperature of the system. But in some answers of ...
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1answer
47 views

Proof of ideal gas equation for container of arbitrary shape (kinetic theory)

While deriving ideal gas equation - we take gas molecules to be contained in a cubical container (convenient shape) , but how do we derive it for a gas inside some arbitrarily shaped container ? I ...
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34 views

Is the universe inside some huge black body? [on hold]

I've been reading about the black body radiation. A perfect black body can absorb all possible wavelengths- which can be put from zero to infinity. But that will depend on the size of the black body ...
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4answers
62 views

Is perfect thermal insulation possible?

Supposing someone says they have a sample of insulanium with the following properties: If you make a thermos out of insulanium, it will keep a drink hot or cold forever. If you put your hand on a ...
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1answer
36 views

Calculation of temperature distribution in bulk glass due to laser heating

I'm trying to figure out how to simplify the problem where laser pulses are focused to a small spot in bulk glass. The waist of the beam is about 20 microns. At the wavelength used there is only two-...
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0answers
22 views

Is the free energy density analytic in temperature at the Kosterlitz-Thouless phase transition?

I know that the KT transition is infinite-order so the free energy density is a smooth (i.e. infinitely differentiable) function of temperature, but is the function actually analytic at the critical ...
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2answers
62 views

What happens to gold under immense pressure? [on hold]

What would happen to gold if you put it under immense atmospheric pressures? For example 2M atmospheres.
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1answer
58 views

Proper definition of Internal energy

In Internal energy of a gas ($U$), we have to include ALL types of energies possible like $KE$, bond energies, nuclear interaction energies, etc.., However we have derived that $U = (f/2)nRT$ from ...
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0answers
25 views

What variables affect a Heat engine's efficiency? (and more)

I'm writing a Minecraft mod and I'm trying to create the equations for the engines players can build. I'm a highschool sophomore, so my knowledge of physics and mathematics is limited. I asked first a ...
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19 views

Where does this data comparing the CMB with Eddington's 'temperature of space' come from?

Eddington estimated the temperature of space assuming that star light would be scattered by interstellar dust. He came pretty close to the temperature of the CMB. http://www.astro.ucla.edu/~wright/...
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3answers
51 views

Theoretical Calculation of Specific Heat of a Gas

I've read that the theoretical specific heat of a monatomic gas (like dissociated hydrogen or oxygen) is $20.8\, \mathrm{\dfrac{J}{mol\cdot K}}$ at constant pressure and $12.5\, \mathrm{\dfrac{J}{mol\...
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0answers
33 views

Why do insulated cooler bags have aluminum on the inside?

I understand that aluminum can partially reflect the sun and other heat radiation if placed on the outside of cooler bags. However, most types of cooler bags only actually have the foil on the inside ...
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2answers
35 views

Thermodynamics- $PVT$ adiabatic system

In thermodynamics, what is a phase? Imagine a container full of air where the walls of this container are adiabatic and there is a piston on the top of it. If we push the piston downwards, the ...
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2answers
36 views

Temperature distribution in a column of air

Say there is a sealed cylinder of air that has a height $\mathrm{h}$ and area $\mathrm{A}$ on the ends. The initial temperature throughout the column is $T_0$ and has a uniform initial density $\rho_0$...
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5answers
2k views

Why does a critical point exist? [duplicate]

I still cannot fully comprehend the essence of a critical point on phase diagrams. It is usually said in textbooks that the difference between liquid and gaseous state of a substance is quantitative ...
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2answers
110 views

Wouldn't the thermodynamic cost of creating alternate universes make the Many Worlds interpretation implausible?

I was thinking about the many interpretations of quantum physics, and one thing that never made sense to me was the many world's interpretation. Basically at any given moment for which something ...
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1answer
67 views

Approximate formula for the volume of water at a given temperature

Sorry for asking this kind of question. Do you recongnize this formula? $$V(T) = 0.0000679T^3+0.0085043T^2- 0.0624T+999.87$$ when $V$ is volume of water in $\mathrm{ml}$, $T$ is temperature in ...
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1answer
49 views

Why don't the less denser steam move up, leaving the more denser water drop to fall on hot pan in Leidenfrost effect?

In Leidenfrost effect, the hot steam suspends water droplets above it and prevent the drop from touching the hot pan. My question is, as the steam is less denser than water, should the steam not ...
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0answers
17 views

Self Heating in Platinum Resistance Thermometers

In order to use a PRT a small excitation current has to be passed through it, which creates a heating effect that in turn adds an error to the measured temperature. The question is this: If we have ...
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0answers
48 views

Mathematical method of Physics [closed]

Please any one can tell me how to get lecture of mathematical method of physics complete course online download complete lecture series. Which professor best for this subject please guide me how to ...
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0answers
29 views

How would you go about solving this difficult diatomic efficiency problem? [closed]

I've tried using the ideal gas law and got the following answer: (5/2)*4*8.31451*140 =11640.314 J. However, I don't know what to do next...?
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15 views

Question about a particular thermal shock scenario

I watched this video https://www.youtube.com/watch?v=xbuvcQrAOSk Where they heat up a pyrex pot and then add a few drops of cold water to see how the pot will react (while shooting the scene with a ...
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1answer
13 views

Multiplicity Identity in Kittel's Thermal Physics

On page 25 of Kittel's Thermal Physics, the author derives the multiplicity of $N$ harmonic oscillators with total quanta of energy $n$, $g(N,n)$. He writes \begin{align} g(N,n) &= \lim_{t\...
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45 views

Why isn't mass conservation counted among the laws of thermodynamics? [on hold]

Is this purely a historical artifact, a consequence of how the original formulators of the three laws were thinking and experimenting at the time? Or is there a compelling scientific/logical reason ...
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2answers
52 views

Is energy only transmitted through electromagnetic and particle radiations? [on hold]

Which are the other ways of transmission if any? If energy does not require any medium for transmission(as for sunlight reaching earth, the heat too), is it transmitted in quanta in particle radiation ...
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0answers
8 views

Pressure factor affecting reversibility of a process [duplicate]

It is said that for a finite pressure difference between system and the surrounding the process is irreversible. From the diagram can you please tell me how the process is irreversible ? Does this ...
3
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1answer
212 views

Will heat flow by conduction oscillate until thermodynamic equilibrium is reached in a solid object?

Consider the following thought experiment with $2$ conducting objects $A$ and $B$, where object $A$ is initially at a much higher temperature than object $B$. The objects are now placed in perfect ...
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2answers
118 views

Please explain entropy curve [closed]

I saw this curve at a website, but I didn't understand it. What is the lower point of entropy, and what are the points A, B, and C? Thanks!
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0answers
22 views

Can sudden thermal contraction fix hail dents? [closed]

I recently bought a car with some hail damage, and someone told me that you can fix the exterior dents by throwing ice on (for instance) the dented hood. I'm a bit skeptical of fixing dents caused by ...
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1answer
89 views

How does eating a cold ice cream actually heat up your body? [closed]

The question is the title itself. During winter one of my friend told we'll have an ice cream. And rest of us where like are you nuts. He was like cold ice-cream actually heats up your body. Even I ...
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1answer
84 views

What is the name of matter with $w = - \frac{1}{3}$?

What kind of "matter" is described by the following thermodynamic relation ? \begin{equation}\tag{1} p = -\, \frac{1}{3} \; \rho, \end{equation} Where $p$ and $\rho$ are the pressure and density ...
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3answers
49 views

Why does heating a room by a set degrees depend on the absolute temperature?

I'm learning about coefficient of performance (COP) and am trying to understand its implications for heating/cooling. By intuition I assumed heating or cooling a room by a set amount requires the ...
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1answer
61 views

Covariant Taylor Series

I am reading the following lecture notes of Avramidi https://www.researchgate.net/publication/255565392_Analytic_and_geometric_methods_for_heat_kernel_applications_in_finance I want to understand ...
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2answers
45 views

Pressure Difference affecting reversibility of a process

It is said that for a finite pressuredifference between system and the surrounding the process is irreversible. From the diagram can you please tell me how the process is irreversible ? Does this ...
0
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2answers
63 views

How does viscosity cause dissipation? [closed]

I am not a physicist so bear with me. I'm trying to understand the mechanism through which energy is dissipated in a fluid or solid. Often the explanation is that it happens due to viscosity or ...
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0answers
49 views

Solving global warming? [closed]

Are you willing to consider a different approach to solving global warming? I have done this, even designed and conducted an experiment and gathered data, yet I can't seem to convince anyone to give ...
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2answers
74 views

Why does hot water freezes faster than normal water? [duplicate]

What is the reason behind hot water gets Freezes faster than normal water when we keep both the hot and normal water together in freezer ?
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1answer
41 views

Avoiding a Divide by Zero with Absolute Entropy

I've been reading that unlike enthalpy, entropy has an absolute value that we obtain by setting it equal to zero at absolute zero temperature, but I'm having a hard time understanding how to avoid a ...
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1answer
59 views

Thermodynamics - Partial Derivatives [closed]

I just need help to solve a problem: $\left(\frac{∂\overline{E}}{∂V}\right)_{β,N} + β\left(\frac{∂\overline{p}}{∂β}\right)_{N,V} = - \overline{p}$ PS: The bar over E and over p (this in both sides) ...
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1answer
35 views

Application of Carnot's theorem to calculate efficiency of thermal engine

I understood Carnot's theorem in theory, but I still have some doubt on the practical use of it. In particular I would like to know: if I have any reversible cycle followed by a gas, then the thermal ...
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1answer
33 views

Consideration on the total entropy variation for 2 ideal gases

Let's consider an isolated container containing a mole of an ideal monoatomic gas $A$ and a mole of a biatomic gas $B$, separated by an ideal piston (hermetic). The gases slowly exchanges heat and the ...
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1answer
83 views

When is ${d}\,Q=T\,dS$ not true? [closed]

Why is the first T differentiated from the second in $T\,\frac{{\rm d}\,Q}{T}$ ? So why do we use a product to express this and not just ${d}\,Q$ , which goes hand in hand with the cases where $dS&...
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1answer
36 views

Is there a thermodynamical function $\Xi$ such that $d \Xi = V d P/H$?

Question Is there a thermodynamical function $\Xi$ such that generally $$d \Xi = \frac{V d P}{H}$$ where $V$ is the volume, $P$ the pressure, and H the enthalpy $H=U + PV$? If such a function ...
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1answer
49 views

Why does a heatsink level out at “a temperature”

Lets assume I'm talking about a computer-type aluminium heatsink, which has a constant thermal load into its base. Over this heatsink moves air at a constant rate, and a constant temperature. Why ...
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1answer
64 views

Entropy change of an irreversible process

I know that there's a lot of questions about this subject but I couldn't find specifically what I want to ask so here it is: One of the consequences of Clausius's theorem is the fact that for any ...
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1answer
27 views

Difference in steaming with superheated steam to saturated steam in coffee beverages

Coffee machines are emerging on the market which claim to superheat the steam they use in heating and aerating milk via a submerged nozzle for latte/cappuccino type beverages. So instead of the ...
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0answers
41 views

Is the vacuum state of a quantum field necessarily zero temperature?

A statement in Quantum field theory: zero vs. finite temperature points to temperature as it relates to the vacuum as being a matter of definition. In that post, Will states By, "at zero ...