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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2answers
51 views

Is the relation between expansion of a liquid with temperature linear?

Say I have a liquid with certain volume. If I heat it, will it expand with a constant rate? $$ \frac{T}{V} = k.$$ It is true for gases, is it also true for liquids? And if yes then: is it true for ...
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0answers
24 views

How to calculate the heating power of a metal plate in nature?

I like to heat up a part of a metal plate to a given temperature. For that I want to use an electric heater. The metal plate is located outside in nature. For that I need to take in account the wind ...
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0answers
14 views

Are elements of statistical ensemble fixed or dynamic?

I will use the simplest example I can think of to explain what I am trying to understand. Consider a system with ~10^23 particles in an equilibrium with fixed values of pressure, volume and ...
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1answer
21 views

Heat transfer direction in fins

I'm unsure of what exactly is changing the heat transfer direction in the triangular fin. $$q_{x} = -kA(x)\frac{dT(x)}{dx} (1)$$ $$q_{x+dx} = -kA(x)\frac{dT(x)}{dx} - k\frac{d}{dx}[A(x)\frac{dT(x)}{...
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3answers
107 views

Is this explanation for the Universe's low entropy at its origins plausible? [on hold]

I've been thinking about this, and it may sound very ludicrous (and it probably is), but I may have come up with a proto-explanation for it. I hope I won't come across as some misinformed perpetual ...
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2answers
49 views

Heated and cooled air effects on combustion

In a turbocharged engine, an intercooler is installed to cool down the compressed air (apparently for better combustion). In contrast, in the power plant they use air preheater to heat up the air ...
2
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2answers
53 views

How is 'Fog' in summer (sea-elevation) possible?

I am residing in New Delhi (pardon me for any irrelevant data I might include), and I noticed a really interesting thing. It's an average $30^{\circ}\mathrm{C}$ out here, and yet, most/some weather ...
2
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1answer
35 views

Extinction level meteor effects on Earth's crust pending on the surface area upon impact

Would it be possible to have a extinction level meteor hit Earth depending on shape to actually create minimal damage if turned on its thinnest area rather than hitting flat? The meteor would enter ...
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2answers
206 views

Is ergodic hypothesis in contradiction with the notion of equilibrium?

From wikipedia: In physics and thermodynamics, the ergodic hypothesis1 says that, over long periods of time, the time spent by a system in some region of the phase space of microstates with the ...
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1answer
52 views

Why is black hole entropy not an extensive quantity?

The Bekenstein entropy for a black hole is proportional to the surface area $A$ of the black hole $$ S_{BH} = \frac{k_B}{4 l_P} A $$ with the Planck length $l_P = \sqrt{\frac{\hbar G}{c^3}}$. The ...
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2answers
885 views

Does fluid speed affect liquid cooling?

If you have a liquid-based cooling system, like the loop in the picture below, does the fluid speed actually matter? I can see how cycling the liquid too slowly would be bad, since the fluid would be ...
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0answers
31 views

Why does depth and height replace volume in this problem? [on hold]

In the following problem, why does H/𝛿 replace V/V? The two ratios have different units. Is there something I'm missing here?
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3answers
95 views

How much water did I actually drink? [on hold]

Water expands at temperatures over $5^\circ\mathrm C$ strictly monotonic. If you now drink $1~\mathrm{L}$ water ($5^\circ\mathrm C$) which will expand in your body on $37^\circ\mathrm C$, did you ...
3
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2answers
62 views

If we harvest energy generated by Coriolis Effect of the earth, will the earth slow down?

Coriolis Effect causes strong winds in the upper atmosphere, and it's purely due to differences in the linear velocity of Earth's rotation across latitudes. Now the Earth is spinning with the energy ...
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1answer
24 views

Heating water in a pot from a constant heat source

What are the equations used to calculate the amount of energy transferred from a constant heat source "like a stove" to a pot which would then transferred energy to water contained in that pot. I don'...
3
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1answer
35 views

Is it possible to quantify the work required to introduce order?

Is there a thermodynamic analysis that allows us to say "in order to introduce this much order into this subsystem, this much work must have been done on it by the rest of the system"? I assume that ...
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0answers
22 views

How to find the change in internal energy for a gas? [on hold]

So I'm given this problem, and for some reason when I solve for Q and delta U my answer is off, should be $\Delta U = 249.3J$ and $Q = 415.5J$ ...
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0answers
27 views

Is there a maximum temperature? [duplicate]

I have read about absolute zero. I understand that it is impossible to cool a system below absolute zero (or to absolute zero for that matter). However, is there a maximum temperature? My intuition ...
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0answers
8 views

Infer geophysical underground structure from thermal photography of the ground

Is it possible to determine (approximately of course) the geophysical structure of the underground under a certain region, using only a thermographic picture of the upper ground of the region ? The ...
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1answer
42 views

Does the shape of a meteor make any difference during an impact? [on hold]

Would the shape of the meteor make a difference on the impact? Like a Olympic diver would a spear shaped meteor make less damage to the surface of the Earth while creating more magma movement rather ...
3
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0answers
62 views

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
16 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
78 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 ...
3
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1answer
53 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
55 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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0answers
35 views

Is the universe inside some huge black body? [closed]

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 ...
2
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5answers
91 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
41 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-...
2
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0answers
24 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
66 views

What happens to gold under immense pressure? [closed]

What would happen to gold if you put it under immense atmospheric pressures? For example 2M atmospheres.
0
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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
26 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 ...
3
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0answers
20 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
52 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\...
3
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0answers
37 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
36 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
38 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 $\rho_0$...
27
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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 ...
5
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2answers
113 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 ...
2
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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 ...
0
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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
49 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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0answers
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 ...
0
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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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0answers
46 views

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

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 ...
1
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2answers
53 views

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

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
213 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 ...