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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What happens to heat waste produced by energy generation?

What happens to heat waste produced by energy generation on earth that must be there according to the laws of thermodynamics? So, it never dissipates and remains on earth?
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20 views

Why (and how) do foods stick to a pan?

We all (sooner or later) have noticed that foods relatively high in protein (especially those low in fat) are very prone to sticking to a pan, or in general to any non-specially-coated metal surface. ...
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3answers
61 views

Is heat a property of Something?

There are some unique properties of things in our world. For example, charge is a property of mass. Is heat a unique property of something? Can a vacuum/void have a finite amount of heat in it? What ...
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1answer
20 views

Vapour from a vessel's opening? [on hold]

I just noticed something interesting while I was in the chemistry lab. I heated some liquid( about 60 mL. Which consists of 20 mL of Oxalic acid solution and 20 mL of $H_2SO_4$) in a conical flask to ...
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1answer
54 views

How much pressure would be needed to contain a 1 gigaton nuclear bomb explosion within a sphere of one meter radius?

How much pressure would be needed to contain the largest human exploitable nuclear bomb within a sphere of one radius? Also would it be possible to create a magnetic field that controlled some ...
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4answers
218 views

Is thermodynamic free energy and potential energy the same thing?

The equation for free energy $F$ and potential energy $E_{pot}$ are: $$ F=U-TS \\ E_{pot} = E_{tot} -E_{kin} $$ But the temperature $T$ is proportional to the average kinetic energy of a system. So ...
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1answer
65 views

Does car colour affect car temperature? [duplicate]

My family will buy a car, so to minimise the car's air conditioning and heating (and thus fuel) costs, how should we choose a car exterior's colour and the interior's colour and material (eg fabric ...
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1answer
95 views

Rayleigh-Taylor Instability dependence on acceleration direction

I'm trying to bolster my understanding of the Rayleigh-Taylor instability, and I've gotten stuck on the point of which fluid (more or less dense) is being accelerated into the other. Cases of uniform ...
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2answers
600 views

Symbols of derivatives

What is the exact use of the symbols $\partial$, $\delta$ and $\mathrm{d}$ in derivatives in physics? How are they different and when are they used? It would be nice to get that settled once and for ...
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1answer
63 views

Unmixing of gases: What is the relevant temperature for my Entropy?

This answer to a question about unmixing gases states: However, let us now assume we have to hand a source of mechanical work, and a large heat reservoir at temperature $T$. I'll assume that ...
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1answer
63 views

If I take a bottle of air into space, and open it, then close it and come back to earth and open it one last time, what would happen?

I was reading this post, but no one seem to go further as say what would happen if you brought the bottle back to Earth? Guess what another thing I'm wanting got know is, what would now be in the ...
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2answers
983 views

Simple thermodynamics basics - can internal energy be calculated?

Well this got me stumbled, because I've been wondering what the "question" is. One of the example examns got the following question (strangely there are no supplied solution books): A $0.2 {\rm ...
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5answers
786 views

What is the meaning of following expression $C=\frac{\delta Q}{dT}$ mathematically?

Our professor raised the following question during our lecture in Statistical Physics (even so it's related to Thermodynamics): Many text books (even Wikipedia) writes wrong expressions (from ...
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0answers
56 views

Understanding the physical applications of the Laplacian: Finding the heat-equation using the continuity equation [on hold]

I know the following: $$q=\rho c T$$ Where $q$ is heat per unit of volume, $\rho$ is the density, $c$ is the specific heat capacity and $T$ is the temperature. The flow of heat is given by: $$\vec ...
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1answer
73 views

Derivation of temperature-volume relationship for a reversible adiabatic expansion of an ideal gas

We start with $\delta q = 0$ and $dU = C_{V}(T)dT = \delta w$. Why can we take the heat capacity at constant volume, when this process is an expansion so volume increases?
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0answers
18 views

Thermal Conduction with multilayered system

Sorry this question probably has a really simple answer but I have been looking and I can't figure out how to solve this problem. I know that the equation for power loss through conduction is ...
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2answers
171 views

Coarse graining on measurement vs phase space (second law)

I've followed Leonard Susskinds series on "the theoretical minimum". In the entropy/reversibility episode in statistical mechanics, he explains (at least one way of) how the apparent paradox of ...
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1answer
982 views

A Christmas Story question!

since the Christmas season is here, I would like to ask a question about the movie, "A Christmas Story." In one of the subplots of the movie, Ralphie's friends were betting each other that their ...
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1answer
322 views

Does a negative line tension in a 3-fluid immiscible interface make sense?

This question is inspired by this question/answer pair: Is this formula for the energy of a configuration of 3 fluids physically reasonable? Consider three immiscible fluids forming contact surfaces, ...
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3answers
280 views

In what limit do we *really* get Maxwell-Boltzmann statistics from Bose-Einstein and Fermi-Dirac?

Fermi-Dirac and Bose-Einstein energy occupation number $n(\epsilon)$ in natural units ($[T]=[\epsilon]$) read $$n(\epsilon) = \frac{D(\epsilon)}{e^{(\epsilon-\mu)/T}\pm 1},$$ where $D(\epsilon)$ is ...
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0answers
23 views

Callen's “Thermodynamics and an Introduction to Themostatistics” the “most frequently cited thermodynamic reference in physics research literature”? [on hold]

Is Callen's Thermodynamics and an Introduction to Themostatistics really the "most frequently cited thermodynamic reference in physics research literature", as this claims? How would one verify this, ...
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1answer
36 views

Canonical Distribution (Partition Function)

For the canonical distribution $$ w_{n}=e^{(F-E_{n})/T}, $$ is the sum $$ Z=\sum_{n}e^{E_{n}/T} $$ a sum over energies or a sum over states? Perhaps this is a silly question, but Landau and Lifshitz ...
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1answer
92 views

Heat flow in a hollow cylinder

Consider a hollow cylinder of different outer radius and inner radius and two different temperatures are maintained at the outer and inner surfaces such that inner temperature is higher. Because of ...
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1answer
55 views

Spontaneity / Free Energy of Non-Isothermal Process

I'm trying to determine a lower bound for the work input necessary to make an entropy-reducing process "spontaneous" in the sense that the 2nd law is not violated. For a constant temperature and ...
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2answers
569 views

Mechanical Equivalent of Heat

Recently I have been looking up James Joule's experiment regarding the mechanical equivalent of heat. After viewing some drawings of the apparatus, I assumed that the lines holding the weights would ...
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0answers
43 views

How is the Horizon Problem really a problem?

I always thought the uniformity in the temperature of the CMB was supposed to be expected, since it's a much more probable initial condition for the universe. I finally found someone explaining what I ...
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1answer
43 views

Relation between Entropy and Temperature

Entropy is defined in my book as $S = \frac{Q}{T}$. To derive the formula it says that entropy should be directly proportional to the heat energy as with more energy the particles would be flying all ...
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1answer
177 views

Fluids in thermodynamic equlibrium

I am reading about the Euler equations of fluid dynamics from Leveque's Numerical Methods for Conservation Laws (Amazon link). After introducing the mass, momentum and energy equations, some ...
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1answer
29 views

Heat transfer between the bulk of the fluid inside the pipe and the pipe external surface

In an article from Wikipedia about heat transfer coefficients in the section Combining heat transfer coefficients there is an equation which describes the rate of heat transfer between the bulk of the ...
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3answers
98 views

Calculate the rise in temperature from directed radiation [on hold]

For example I have a 1 watt laser and direct it to a sheet of metal (copper), if I were to direct it for say a time interval of 1 minute what would be the change in temperature? I can predict that it ...
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0answers
18 views

How to find Entropy of system in terms of Magnetic Field and Temperature

I'm studying for final exams and I have a question about how to find the entropy of a particular system. The system is a lattice of paramagnetic atoms fixed to the lattice sites, with an external ...
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0answers
13 views

Heat Transfer in Cylindrical Coordinates

Lets say one has an infinitely long cylinder with some boundary heat terms on $r=r_0$ of the form $T(r=r_0, \phi,z)=T_0(\phi,z)$. What is the general solution for this type of equation? The general ...
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1answer
23 views
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1answer
29 views

Grand Canonical Partition Function

I'm looking over posted lecture notes for a course, and this derivation of the Grand Canonical Partition function eludes me. It goes like this: occupation numbers $n_{α}=0,1,…$, Total particle number ...
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1answer
71 views

Modelling multiple heat sources?

I am working on a project to model heat transfer in a data center. I have basic models for a one dimensional heat transfer using conduction and convection. Such as, taking a server and modelling the ...
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1answer
28 views

Does heat at atomic scale present like macroscopic kinetic energy?

Heat energy is described as the kinetic energy of a molecule or atom, but how does that energy present itself? I keep hearing that it's "random", akin to a randomly jittering atom in space, but I'd ...
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53 views

Why does hot food give off vapor?

Does your food melt and then boil to give off this gas? What is the vapor here?.
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1answer
94 views

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

I have the heat balance equation for a cooling case in the form: $$\frac{dU(T(t))}{dt}=-J$$ with $U$: energy (J) $T$: temperature (K) $t$: time (s) $J$: heat flux leaving the system (W) I have ...
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2answers
44 views

If the specific heat capacity depend upon the temperature, what formula we should use instead of $Q=mc\Delta T$

Recently, I learned that specific heat capacity is not constant in different temperatures and it depends on the temperature.If I have diagram like this (consider that the red part is a quarter of ...
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4answers
233 views

How does the formation of a solar system not break the second law of thermodynamics?

Please forgive: I am a layman when it comes to physics and cosmology, and have tried finding an answer to this that I can understand, with no luck. As I understand it, the solar system evolved from a ...
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1answer
19 views

Acceleration of a container in thermodynamics

How will accelerating a container with an ideal gas in it affect the conditions? My initial thoughts are that the ideal gas will collect at the opposite end of acceleration, which means that the ...
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2answers
100 views

Does leaving snow on my hot tub cover save me money?

Snow is supposedly such a good insulator, that some animals dig snow caves in which to hibernate through the winter. However, my hands seem to feel more comfortable being exposed to winter air than to ...
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1answer
81 views

Thermodynamic Internal Energy Reference States

The internal energy, $U$, of a given thermodynamic state, $\boldsymbol{R}$, as introduced in thermodynamics textbooks like Callen seems to be defined as: $U (\boldsymbol{R}) = \Delta U ...
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1answer
25 views

efficiency of a stirling engine with spring

I have used the concept of stirling engine with a spring instead of any gas to make an engine....i want to calculate the efficiency of it...here's a pic:
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1answer
23 views

Change in entropy adiabatic expansion

I think that an adiabatic expansion of a gas should cause the entropy to increase. On the other hand we have for adiabatic processes that $dQ = 0$ and therefore $dS= 0$, which is why I thought that ...
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2answers
77 views

Will heating up an object increase its mass? [duplicate]

According to the $E=mc^2$ equation, will an object whose thermal energy (temperature) rises also weigh more? And by the same token, will the mass of an object decrease as its temperature approaches ...
3
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1answer
75 views

Simple estimation of the critical temperature of water

I'm trying to develop fermi estimation skills and I came up with a question for which I don't even know where to start from. Here goes: Is it possible to estimate the critical temperature (say in ...
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2answers
36 views

Why does room temperature water and metal feel almost as cool as each other?

From what I've read about heat, temperature and conductivity, I understand that the reason water at room temperature feels colder than most other things at the same temperature (like wood, air, ...
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2answers
546 views

Computer cooling with dry ice, ideas and question; thermodynamics

I am designing a cooling system for my computer and had a few questions. So I have a computer water cooling radiator and I want to cool it as much as I can. My first two ideas were an old window A/C ...
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26 views

Why is Cv greater than Cp during anomolous expansion of water?

Well, in general $c_p> c_v$ for most cases but for water having anomolous expansion from $0^{\circ}\mathrm{C}$ to $4^{\circ}\mathrm{C}$ the order is just opposite, $c_v >c_p$, why?