Questions tagged [thermodynamics]

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

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In Feynman lecture Vol1. chapter12 about friction, $F = μN$ will fail because of the excessive heat generated. Why is that?

$F = μN$ will fail because of the excessive heat generated if the normal force or the speed of motion gets too big. Why is that? "$F = μN$, where μ is called the coefficient of friction (Fig. 12-1)....
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Is $A\cos(kx-wt)$ a valid solution to the diffusion equation?

I know that for the wave equation $$\frac{\partial^2\psi}{\partial t^2}=c^2\frac{\partial^2\psi}{\partial x^2} \;, $$ we could always plug in the ansatz $A\cos(kx-\omega t)$, since equations of this ...
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What is the change of entropy in the Universe?

A 10 Ω resistor is held at a temperature of 300 K. A current of 5 A is passed through the resistor for 2 minutes. Ignoring changes in the source of the current, what is the change of entropy in (a) ...
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can low pressure systems act as coolants

I apologise if this is the incorrect way of wording this question but I was wondering about whether for example, a container with very low pressure could cool down its surroundings?
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How did Clausius came up with the idea of his inequality?

I mean I am interested in the story behind it and the proof Clausius himself provided. Any resource or link would be very helpful.
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How does this study affect the holographic principle and holographic screens?

In a recent study (https://www.nature.com/articles/s41467-018-05433-9) an important flaw in Emergent Gravity/Entropic Gravity has been spotted because it has been discovered that holographic screens ...
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Formula of Heat Generated by Continuous or Acute Force Exertion on Elastic Object

See the figure below. Ignoring friction but not elasticity, I am assuming the object will be deformed and heat up by part of the energy transferred by F. What does the general formula to demonstrate ...
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Why does an adiabatic process become an isothermal process when D.O.F. are high?

Say that during an adiabatic process, the pressure changes from $p_0$ to $a*p_0$, and let the heat capacities ratio be denoted by b ; using the basic adiabatic relations for an ideal gas, we can find ...
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Thermodynamic Properties

Suppose a certain quantity of gas is taken in a closed container and then the mass of the gas is doubled keeping the volume and temperature constant. So the pressure of the gas now doubles too. Isn't ...
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What is the smallest stable grain size attainable when grinding an ionic crystalline compound?

If the compound could be ground to molecular size and if the resulting sample were kept in a 'pile' so that these molecules were in contact with each other, then the molecules would tend to bond ...
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Thermodynamic equilibrium in a room , in a real situation

In my class about 50 students were seated in a room. The room was medium sized and it had 2 AC, one in the front and one at the back. The teacher was feeling cold so he switched off the front AC ...
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Prove that the number density is proportional to the mass fraction divided by the molar mass [on hold]

For a mixture of gases, prove that the number density $(N/V)$ of a gas is proportional to its mass fraction divided by the molar mass. My attempt: $N$ is the number of molecules, $N_A$ is Avogadro's ...
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Two black holes in rotation - Energy conservation

I was looking at this problem: Let consider two black holes of mass $M$ rotating around a point $O$ (circular montion). The first black hole center is $M_1$, the second $M_2$. Each of them has ...
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What is the volume occupied?

What is the volume occupied by 1 mole of gas at $10^{−10}$ torr, the pressure inside an “ultra high vacuum” (UHV) chamber. How do I solve this problem without being given the temperature?
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Gibbs-Helmoltz equations

Show that $E = T^2 \frac{\delta (S-ET)}{\delta T} = T^2 \frac{\delta (S)}{\delta T} - \frac{\delta (ET)}{\delta T} =T^2 \frac{\delta (S)}{\delta T} - T^2 \frac{ T\frac{\delta E}{\delta T} - E}{T^2}= T^...
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Can baby universes solve the information paradox?

My question is do baby universes give us a satisfying explanation of the black hole information paradox without violating thermodynamics, or any other established/known physics? My understanding is ...
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If temperature is related to average kinetic energy in an ideal gas, then does speeding up the gas container affect its temperature? [duplicate]

This question is related to the following textbook question: The temperature of an ideal gas is directly proportional to the average kinetic energy of its molecules. If a container of ideal gas is ...
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Finding $\mu(T,v)$ and $\mu(P,v)$ from fundamental equation $s(u,v)$

I need to find $\mu(P,v)$ (where $\mu$ is the chemical potential) and $\mu(T,v)$ for a system whose fundamental equation in the representation of entropy I do know. All the information I have is that ...
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Spinmodel Statistics

Consider a spin model with the following energy with $ \{\sigma\} =(\sigma_1,\sigma_2,...,\sigma_N)$ where each $\sigma$ can take the values: $-s,-s+1,...,-1,0,1,...,s-1,s$ and $E(\{\sigma \}) = \mu H ...
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A Spontaneous Reaction with greater ordering

I wanted to ask a question regarding entropy in a reaction. I was given the reaction $2H_{2}$ (g) + $O_{2}$ (g) $\rightarrow$ $2H_{2}O$ (l) and asked: the overall process is spontaneous but ...
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Thermodynamics of the Earth’s core

Wikipedia presents conflicting data in the article “Tidal Acceleration”. Hopefully one of you experts can clarify this. The torque on the Earth is measured at $3.9 \cdot 10^{16}$ yet the tidal ...
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Usage of relativistic projectiles as a digging mechanism against airless bodies [on hold]

There has been a bit of contention in my online community regarding the performance of multi-hundred gram projectiles travelling at 0.99C; expected to give a yield in the dozens of megaton range. (The ...
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How does vacuum affect an object's temperature?

I have an objected suspended in a vacuum by a very thin point. Thus, it can be heated only at the point of contact? Am I correct in assuming that the object cannot dissipate heat into the vacuum- ...
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Heat transfer through 2 slabs of same material properties, but different thickness

Let'se say we have two walls, wall A and wall B. Both walls are made from the same material, but they differ in thickness. Wall A is L cm, whereas Wall B is L + ΔL cm. Wall A and Wall B make up parts ...
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Boltzmann molecule motion

Boltzmann stipulates that molecules in a hot state (for example air molecules) move towards molecules in a cold state because they have a much higher probability of doing so. (Corrections on this ...
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Realistic problems with connecting solar panels? [closed]

I want to create a small scaffold which can hold a couple small solar panels, none of them bigger than your hand. And I want to connect them all so that if I were to connect it to an output, it could ...
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What are the heat equation boundary conditions with heating?

I'm trying to figure out how to do a simplified model of heat flow through a wall when the wall is also sunlit. The simplified model is a 1-dimensional heat equation, $$\frac{\partial T}{\partial t} = ...
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Equipartition theorem - concerning the square dependence of energy

So the equipartition theorem states that if the energy dependence is square ($\langle\,E\,\rangle= as^2$ + ...(something not dependent on $s$)) then each variable (degree of freedom) contributes ...
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Magnetic Properties under Pulsed Power

If one were to apply 50 kV at 17 A with a pulse width of 100 microseconds and a frequency of 10 Hz across a samarium cobalt magnet, would the magnet reach its Curie temperature during the time when ...
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Why an open tube at both ends suffers resonance? [duplicate]

Why an open tube at both ends suffers resonance when subjected to a sound that propagates through the air with length of where $L / 2$? I already know the methodology to calculate the harmonics in an ...
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Work done by ideal gas under a reversible process which is not isobaric, isochoric, isothermal, adiabatic

First post, sorry for the poor formatting. Question Consider a non adiabatic system closed to mass exchange where an ideal gas traverses along a reversible path from state: to . What is the work ...
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Entropy in non-homogeneous equilibrium states and local thermodynamic equilibrium

My question concerns the possibility of using the hypothesis of local thermodynamic equilibrium for calculate the entropy of a non-homogeneous equilibrium states. For example, let's imagine the ...
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Third Law of Thermodynamics and Thermal Pollution

Unlike coal power plants which produce CO2 and intensify the greenhouse effect, every engine produces thermal pollution because of the constraints on engine efficiency. No engine can convert 100% of ...
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Convert emotion into energy? [closed]

if it were possible to quantify emotion, would it be possible, theoretically, to then convert it into usable energy?
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Temperature of vacuum chamber on Earth

Does the temperature of a vacuum chamber drop if left for 24 hours or more, since some in space in quite cold somewhere and quite hot how does vacuum become cold near to absolute zero.
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How to connect the force applied to a tuning fork and the intensity of sound produced mathematically [closed]

I'm in year 11 and I have a science depth study where I get to conduct and record an experiment of my choosing to do with sound or light waves. I've chosen to conduct an experiment where I am trying ...
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Why is detailed balance required for thermodynamic consistency?

why does the Wegscheider condition or detailed balance have to be true for chemical reactions and what does it mean to violate it in terms of thermodynamics? here is an attempt to derive a simple ...
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Can we concentrate the “cold of the sky” with a parabolic dish to cool things down during the day?

It's well known that we can focus sunlight with a parabolic dish to collect heat. But if we look at the thermal images of the sky we can see that the clear blue sky is quite cool. So by turning the ...
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Does positive total entropy generation means that the entropy generation of the system and the entropy generation of the surroundings are positive too

When I was working on problems related to entropy generation, there was this problem that asks if the process claimed in the problem is possible or not. The solution manual calculated the total ...
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How can I calculate the pressure needed to compress a piece of tubing with a liquid inside?

I want to study the optical properties of a molecule under pressure. The method that I am planning to use to apply the pressure on my sample is the following: A silicone rubber tube is connected to ...
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How everyone can benefit from learning physics? [closed]

What would be benefits of learning physics in a relatively rigorous way (meaning to take a quick look even at the topics that are more advanced, like quantum field theory) for people who don't aspire ...
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Could a refrigeration unit be used to provide useful heating?

I was thinking about refrigerators and air conditioners. They remove the heat from somewhere and put it into somewhere else. But why are we use this usually for cooling, and not so much for heating (I ...
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Question about the definition of the pressure in statistical physics

I learned, that the definition of the pressure in the grand canonical ensemble is $p=-\langle \frac{\partial H}{\partial V}\rangle=\frac{1}{\beta}(\frac{\partial}{\partial V} \ln\Xi$. First thing ...
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ferromagnetic above the Curie temperature paramagnetic?

Why is a ferromagnet above the Curie temperature a paramagnet? Considering me, it's because a paramagnet has a higher entrope and since $\frac{1}{T} = \frac{\partial S}{\partial E}$. If T increases ...
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Grand-canonical ensemble for $dln \mathcal{Z}$ [closed]

I really don't understand how this is done, I understand the first line, but then it looks like de canonical ensemble relations are used, but this is about the grand-canonical ensemble. Essentially I ...
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How does a gas lamp mantle work? Is it just black body radiation?

Old gas lighting often involved a thing called a "mantle" which was a cloth mesh coated with thorium dioxide. The gas flame heated the mantle and the mantle gave off the indoor lighting that people ...
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Tea steeping as a function of infuser

Suppose I have two identical cups, but one has a spherical steel tea infuser and the other has a muslin, both with the same amount of tea. I add boiling water to both. Assume both the infuser and the ...
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joule-thomson coefficient

I'm a little bit in trouble with this table on wikipedia (https://en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect ) Since it says that when the temperature is below the inversion temperature($1/\...
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How to find equation of state of an ideal gas from heat capacity?

I'm having a problem where I have to derive the equation of state of an ideal gas from the formula for molar heat capacity $C=C_V+ \beta V$. Is this even ideal gas? Can someone help me, or at least ...
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Negative Temperature Without Statistical Mechanics

In plenty of the qualitative thermodynamics that predates the statistical description, temperature is assumed to always be positive; many key inequalities related to the second law often involve ...