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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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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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1answer
39 views

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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1answer
38 views

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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1answer
34 views

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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1answer
61 views

Convert emotion into energy? [on hold]

if it were possible to quantify emotion, would it be possible, theoretically, to then convert it into usable energy?
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62 views

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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23 views

How to connect the force applied to a tuning fork and the intensity of sound produced mathematically [on hold]

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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1answer
60 views

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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3answers
78 views

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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4answers
53 views

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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1answer
26 views

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? [on hold]

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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2answers
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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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2answers
58 views

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 $dln \mathcal{Z}$ [on hold]

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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1answer
59 views

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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1answer
22 views

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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1answer
52 views

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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1answer
40 views

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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1answer
54 views

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 ...
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3answers
79 views

Infinite entropy in ideal gas

Does it make sense that entropy goes to infinity as temperature goes to infinity? For an ideal monoatomic 1D gas I have an expression for entropy \begin{equation} S=Nk_{B}Ln(\frac{Ve^{\frac{5}{2}}\...
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No Schottky anomaly in the case of the heat capacity $C_{V}(T)$ of a harmonic oscillator?

Why is there no Schottky anomaly in the heat capacity $C_{V}(T)$ of a harmonic oscillator? There are Schottky anomalies present in 2-level/N-level systems with equal spacing between levels. ...
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19 views

Schottky anomaly in the heat capacity $C_{V}(T)$ of a 2-level system

Why does the Schottky anomaly in the heat capacity ($C_{V}(T)$ against $T$) associated with a 2-level system with energy spacing $E$ appear at $k_{B}T\approx\frac{E}{2}$ (a precise calculation gives $...
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26 views

At thermal equilibrium, do the energies of the 2 systems equalize?

Suppose we have 2 systems with energies $E_1$ and $E_2$ respectively that are in contact with each other until thermalization occurs. The temperatures of the 2 systems equalize but do the energies $...
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3answers
68 views

Entropy generation of constant volume heat addition process

For an ideal gas constant volume heat addition process, change of entropy equation is: $$\Delta S= c_v \ln\frac{T_2}{T_1}+ R \ln\frac{v_2}{v_1}= \int \frac{dq}{T}+S_{gen}$$ The term $R \ln\frac{...
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28 views

Should it work?(waterless cooling system) [closed]

The presented Idea is based on Heat exchange principle. As per sketch there will be a conveyor belt system and some copper stripes will be connected with this belt. Each copper strip will have a ...
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1answer
15 views

Can a non-quasi-static process have an equation of the path which it has followed?

Recently I saw a question where there was a specific p-v relation for a process, but it was stated that it's not a quasi-static process. Hence, we can not calculate the work done by integration of pdv ...
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0answers
49 views

What does this paper talk about? and Does Ricci flow have some application in general relativity? [on hold]

https://arxiv.org/abs/gr-qc/0602054 who has read and studied this paper, and if we can apply ricci flow to GR? if so, it is known that ricci usually is limited in positive remiann manifold, and ...
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4answers
117 views

First law of thermodynamics differential form doubt

For the first law of thermodynamics, we have that $Q-W=\Delta U$ Since there is a variation of the values of the thermodynamic variables, because of Q and W, there is a variation of internal energy....
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boundary conditions in QM and statistical physics

I don't understand something about boundary conditions in problem that I discuss it below. in QM we solve the particle in Potential well and we obtain that we should have $k=\frac{n*pi}L$ that $n\in{...
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3answers
36 views

Partial molar volume and constant composition

Why is it necessary that the composition of a mixture (with 2 components A and B) remains constant to arrive at this equation $$ \begin{aligned} V &=\int_{0}^{n_{A}} V_{\mathrm{A}} \mathrm{d} n_{\...
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1answer
27 views

Absence of dissipative forces in a reversible process

I can't understand why dissipative forces must be absent during a reversible transformation. Aren't they a way of exchanging heat with ambient? Since the system is allowed to exchange heat with the ...
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If we assume constant Temperature and Pressure, why isn't the Change in Gibbs Free Energy always 0?

The Gibbs Free Energy is defined as: $$G = U + PV - TS$$ If we assume that the temperature $T$ and the Pressure $P$ are constant, then any change in the Gibbs Free Energy would be: $$\Delta G = \...
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1answer
56 views

How does sound melt concrete?

The sound power level (SPL) of the Saturn V rocket engines were 220 db. There are numerous websites that state this is loud enough to melt concrete. An example from the website makeitlouder.com 220 (...
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2answers
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A heat flow generalized problem featuring light bulb and oven

If an incandescent light bulb under constant power is taken from room temperature 25 deg C to an oven at 75 deg C, does the filament temperature increase by 50 C? Assume radiated power is negligible ...
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1answer
29 views

Why does the Einstein relation hold in the derivation of the Goldman equation?

The Einstein relation $D = \mu k_B T$ is derived by assuming an equilibrium between the drift current and the diffusion current. Knowing this I would assume, that the relation is only valid under this ...
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1answer
41 views

How does heat is generated during nuclear reaction

In a nuclear reaction 235-U is being constantly divided under high neutron flux. After the division we get 2-3 neutrons with high energy and fission products with its own energy. My question is from ...
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1answer
44 views

Another Free Energy Question :P :)

Hello StackExchange users. Before you read my question I would like to thank you for taking the time to help me out :). So anyways, my question is about the formation of coal seeming to break the laws ...
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1answer
26 views

zero specific heat for infinite temperature

Why in a two possible energies system heat capacity goes to zero as the temperature goes to infinity? I thought as T increases heat capacity approached to a constant positive number, however I'm ...
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1answer
23 views

How prioritize between conservation of angular momentum and the equipartition theorem?

In most or all description of gas equilibrium the equipartition theorem is used to motivate that energy es equally distributed between rotating and linearly oscillating modes? How can that be since ...
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2answers
48 views

Can Entropy Change be negative in this situation?

The temperature of two moles of an ideal diatomic gas is decreased from 𝟔𝟎𝟎 𝐊 to 𝟑𝟎𝟎 𝐊 at constant pressure. Is entropy change negative?
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1answer
42 views

Earth's Effective Area

Let's suppose the Earth is a black body. Usually, when determining its energy balance, the following approximation is taken into consideration: $$ \pi R_{Earth} ^2 I_{Sun} = \sigma T_{Earth} ^4 4\pi ...
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2answers
171 views

How can work be generated from quantum correlations?

There are several articles (like this or this one) concerning extracting work from (quantum and/or classical) correlations. Nevertheless, these articles appear to be quite dense and without showcasing ...
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22 views

Joule's heating effect

Can we derive joule heating effect or heating of current using energy conservation for electrons when current is varying with time ?Like using concept of drift velocity,potential diffrence across ...
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1answer
63 views

Why don’t ALL polymers collapse even when their compact state would clearly be favoured in terms of having a lower Helmholtz free energy?

This question is based on example 8.3 in Molecular Driving Forces, Dill and Bromberg (https://books.google.ch/books?id=1gYPBAAAQBAJ&pg=PA136&lpg=PA136&dq=polymer+collapse+a+toy+model&...
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2answers
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Why is the length of the Kelvin unit of temperature equal to that of the Celsius unit? [duplicate]

The Celsius unit is arbitrarily defined, based on the boiling and freezing point of water. Is it a coincidence, then, that the SI unit of temperature Kelvin, which is used in all natural equations, ...
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3answers
76 views

Are there gases that cool down as energy is added?

If there are, please provide examples. Lee Smolin suggests there are such gases in his book, "Time Reborn", but searching on my own, I could not find examples, and it seems hard to accept this is ...