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Questions tagged [thermodynamics]

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

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Effect of condensation pressure drop in open flow

If saturated gas flows through a tube that is being cooled, the gas will start to condense, forming droplets at some point in the tube. Looking at the individual condensation "cells", I ...
Felix's user avatar
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Type of expansion process for a tank with orifice

Consider a tank filled with gas who is being discharged via an orifice. So, the gas flowing out of the tank is experiencing isenthalpic expansion and thereby a specific temperature drop, depending on ...
Felix's user avatar
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Describe the ways that each planet of our solar system dumps energy [closed]

Describe the ways that each planet of our solar system dumps energy.
user416035's user avatar
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Why doesn't capture of infinitely rare ions by microbes in an infinitely large ocean cost infinite free energy?

Sorry if the question title is misleading, but: Suppose we have a single "cell" with internal volume $V_c$ and with a single potassium receptor, in an ocean of volume $V$ which contains a ...
user56834's user avatar
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Does doing work on system increase or decrease its internal energy?

I am currently reading about the 1st law of thermodynamics, from the book "A Hot Story" by G. Venkataraman. While discussing the law, the author tells that when we do work on the system, its ...
Anindita Sarkar's user avatar
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Calculation problem for Berry phase [closed]

The following content comes from david tong lecture notes on quantum hall effect, p34-35. The resulting Berry curvature in polar coordinates is$ \mathcal{F}_{\theta \phi} = \frac{\partial A_{\phi}}{\...
sett the guy's user avatar
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2 answers
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Contradiction in the Carnot Cycle?

The carnot cycle is reversible, because the temperature difference between heat reservoir and fluid is extremely low, so that heat can flow in both directions. Also, the carnot cycle is described as ...
Theiserino's user avatar
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Enthalpy at constant pressure/volume

Enthalpy is defined as the heat the goes into (leaves) a system at constant pressure. $dH =TdS+ d(PV) = TdS + PdV + VdP$ For some reason, most texts simply write $dH = TdS + VdP$ but haven't they ...
David's user avatar
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Calculating a space and time dependant temeprature profile of a very cylindrical heat source in an infinite medium [closed]

I am trying to calculate the time and space depenadant temperature profile of an infinite medium after inserting a very long cylindrical heat source into it using Green's function. The heat source ...
Marija Marolt's user avatar
3 votes
2 answers
404 views

Why is Sun's energy entropy low on Earth?

Warning i dont have physics background, having said that i was recently looking into sun's radiation energy entropy and i had couple of questions. So it is said that we can utilize the energy from the ...
Marinos Eftichiou's user avatar
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Thermal flunctuations of density in thermal equlibrium? [closed]

According to physics a fluid or gas in thermal equilibrium is not exactly homogeneous. Locally its density undergoes random fluctuations which are small compared to the corresponding equilibrium value....
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Is the energy spectrum of molecules of an ideal gas at equilibrium in an isolated system the Maxwell-Boltzmann distribution? [closed]

The energy spectrum of an ideal gas at equilibrium in a closed system at thermal equilibrium with its surroundings is described by the Maxwell-Boltzmann distribution. If the system is then isolated ...
Arthur Goldman's user avatar
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How quickly can you reduce temperature of content in a jar by running cold water over it? [closed]

If I have a glass jar with a metal lid that contains 24floz of water @ 70F and I continuously run 45F water over the top of the closed jar, how long will it take for the 24fl oz to reach 45F?
Eric Shanfeld's user avatar
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The usage of temperature in quantum mechanics

This is a follow up question for my previous question, because now I am more confused than I was before. In a regular quantum mechanics course, temperature plays no role as it does not appear in the ...
MathMath's user avatar
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Isentropic or isenthalpic expansion for the remaining fluid in a previously pressurised tank? [closed]

Imagine a container filled with ammonia at 25 bar and 100 degC. Assume that an orifice is opened, so that fluid can flow through ...
Felix's user avatar
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1 vote
6 answers
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Heating an object with black body radiation to above the temperature of the source

A recent question and its answers say that you could not use sunlight to heat something to above the temperature of the Sun. There was some discussion of the need for the bodies to be in ...
badjohn's user avatar
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When is the temperature relevant for a quantum many body system?

Let me illustrate my question with an example. Suppose I want to consider a system of $N$ identical bosons. The Hamiltonian of the system is typically of the form: $$H_{N} = \sum_{j=1}^{N}(-\Delta_{x_{...
MathMath's user avatar
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Does color temperature limit how much a laser of a given wavelength can heat a target?

The Sun has a peak wavelength of around 500 nm and an effective surface temperature of 5770 K, and sunlight cannot be focused to make something hotter than the Sun, because this would be heat flowing ...
causative's user avatar
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Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

In my book, Concise Physics of Selina Publications for Class IX, it's written there that "If there is no transfer of heat between the two bodies placed in contact, they are said to be at the same ...
Kakiaririki's user avatar
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Where can I find the derivation of the law of mass action for liquids?

I already asked this in chemistry and all they gave me was a link to the historical derivation. https://chemistry.stackexchange.com/q/68195/ But this derivation relies on the Maxwell-Botlzmann ...
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When does equilibrium mean accessible microstates are represented with equal probability in an ensemble of systems?

I'm confused to when a system in equilibrium is to be found in any one of its acessible states with equal probability (accoriding to the postulate of equal a priori probabilities). Reif in his book ...
David's user avatar
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In summer when air temperature higher than 37 degree celsius, is it better to wear more clothes to keep cool? [duplicate]

Usually wearing more clothes will keep us warm, as we did in winter. In summer, we wear less to allow better heat dissipation to keep us cool. However, according to the Second Law of Thermodynamics, ...
Harry's user avatar
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Definition of heat from stat phys [duplicate]

I don't really understand how to couple the idea of entropy as info with heat. Let's say that you have an isolated system. A cube with a a series of movable partitions parallel to a face of the curve. ...
Lina Jane's user avatar
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Energy output calculations for the very big heat exchanger [closed]

It recently emerged the concept of using deep wells as heat exchangers. It can be visualized as a long (2000 m) vertical tube with an inner diameter of 162 mm (the outer pipe diameter is 177.8 mm, ...
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Trouble understanding the classic approximation of a black body as a hole on a cavity

While studying the Rayleigh-Jeans attempt to explain the spectral energy distribution of black bodies I have trouble understanding the concept of a black body as a small hole on a cavity. We define a ...
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Why does capillary in gas thermometer have a temperature and pressure gradient?

I have been learning thermodynamics using Heat and Thermodynamics by Zemansky, in which he mentions The gas in the capillary connecting the bulb with the manometer has a temperature gradient, that is,...
Sanjay's user avatar
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2 answers
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Why there is a delay before canned fruits float to the top?

This question may appear silly compared to others asked on this site, yet, I can't get my head around it. After pouring boiling water into a canning jar with berries, berries stay at the bottom of the ...
g00dds's user avatar
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Optimizing cooling time of water in a bottle with ice [closed]

I'm trying to determine the most efficient way to chill water in a bottle using ice. Here's the scenario: We have a bottle with a volume of $V_1$ liters. We initially add $V_2$ liters $V_2 < V_1$ ...
pie's user avatar
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1 answer
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Can particles feel hot to the touch? [closed]

The other day, I got a tiny splash of hot cooking oil on my hand. But I could barely feel it because it was so small. That made me wonder: how hot would a small collection of atoms need to be for me ...
Dennis Hackethal's user avatar
2 votes
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Pressure dependence on temperature [closed]

I was doing a problem on airflow around a wing, and how water will condensate on a point on the back of the wing. After reading the solution, it said that "The relative change of the pressure of ...
Emil Sriram's user avatar
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1 answer
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Will a Modified Maxwellian Demon Experiment Using Charged Particles Be Able to Recycle Heat?

(If necessary this experiment can be conducted in an environment where gravity is negligible to avoid gravitational effects.) Two adjacent containers are filled with a homogenous gas composed of ...
Jacob Miller's user avatar
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Why does the temperature-volume diagram look the way it does?

Suppose we have a piston-cylinder system containing compressed water (water that is not about to vaporize). The pressure of water is equal to the sum of atmospheric pressure and the pressure exerted ...
Kakashi's user avatar
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3 answers
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How is the change in internal energy zero for the following scenario:

in the problem, they are removing partitions one by one. when they remove the first partition they've mentioned in the solution that internal energy will remain constant in the process (and after ...
khan zaid's user avatar
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2 answers
44 views

Could you make a fire torch with electricity? [closed]

Similar to a blowtorch, is there a way to generate a flame without using gas or liquid fuel(like butane, propane, etc)? (source) For example I'm thinking about those portable air heaters, could one ...
Gabe's user avatar
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Why Does Every Member of the Ensemble Perform Work Equal to the Change in Free Energy During a Quasiequilibrium Process?

I'm studying Jarzynski's 1997 paper on the Jarzynski Equality. In the second part of the proof (from equation (9) to equation (10) in the paper), Jarzynski considers the following process: considering ...
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16 votes
5 answers
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How to turn a sum into an integral?

In, An Introduction to Thermal Physics, page 235, Schroder wants to evaluate the partition function $$Z_{tot}=\sum_0^\infty (2j+1)e^{-j(j+1)\epsilon/kT}$$ in the limit that $kT\gg\epsilon$, thus he ...
GedankenExperimentalist's user avatar
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2 answers
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Regarding the absorption property of a blackbody

Consider a blackbody of surface area $S_b$ and at temperature $T_b$. It is placed inside an evacuated chamber (to neglect all the effects of convection), with walls of chamber at temperature $T_c$ and ...
CP of Physics 's user avatar
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Energy range when deriving heat capacity in Sommerfeld model

In my textbook, they assume a scenario in which the thermal energy of electrons is $k_BT << E_F$ , then only electrons which are near the Fermi level could be excited due to external thermal ...
Thành Nguyễn's user avatar
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What would the temperature of the tropics be if the atmosphere did not try to balance out heat the latitudinal surplus and deficit

The atmosphere acts to even out the heat imbalnce between the surplus at the tropics and the deficit at the poles. Assuming that the composition and density of the atmosphere stay the same, what ...
Geoff Parsons's user avatar
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1 answer
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Argument for relationship between density of states and degrees of freedom and energy

From Reif's Fundamentals of Statistical and Thermal Physics chapter 2.5 Behaviour of the density of states: Can anyone give a clear explanation for why the density of varies rapidly as Energy ($E$) ...
David's user avatar
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1 vote
2 answers
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Which kinds of systems are described by a heat equation?

Every extensive thermodynamic variable has a continuity equation associated to it: $$\frac{\partial \rho}{\partial t}+\vec \nabla \cdot \vec J=0$$ where $\rho$ is the density of said variable and $\...
Lagrangiano's user avatar
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Thermodynamics exercise on transformations

An exercise in my book states the following: n = 0.42 moles of an ideal biatomic gas are stored in an adiabatic cylinder with volume $V = 10^{-2} \text{ m}^3$, with an initial pressure equal to one ...
NICOLA TROMBINI's user avatar
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3 answers
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Should the air specific heat ratio be included in the ideal gas law or not?

As you can see, both equations use the ideal gas low with the universal gas constant in J/kg.k Both equations are used in published articles as follows: "Application of dynamic programming to the ...
Ameen Mohamed Bassam's user avatar
1 vote
2 answers
44 views

Cooling properties of trees and thermal radiation

A question about trees, shading and thermal radiation: Will the shaded area under trees have lower average air temperature than adjacent non-shaded areas? On the one hand, I've read that the real air ...
user131627's user avatar
1 vote
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Does the isotropy definition of a perfect fluid imply no heat conduction?

Weinberg defines a perfect fluid (Chapter 2, Section 10) as one where each fluid element appears isotropic in a reference frame moving with that element. From the definition of the stress-energy ...
Khun Chang's user avatar
2 votes
1 answer
49 views

Two interacting blackbodies (one inside another) - when will thermal equilibrium be attained? [closed]

As I understand it, an ideal blackbody absorbs (and subsequently starts emitting) all incoming radiation. In typical setups like determining a planet's temperature given its albedo and distance from a ...
Faiyaz's user avatar
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2 votes
1 answer
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Helmholtz decomposition of flow at non-equilibrium steady state

I'm trying to work through Karl Friston's mathematical derivation of the Free Energy Principle from Langevin Dynamics (see this paper). I'm confused about the part at the end of page 8 where he uses ...
Ariel's user avatar
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2 votes
0 answers
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How can we calculate entropy produced by plastic deformation in this example?

Suppose we have a massless spring of spring constant $k$ attached to a mass $m$ at equilibrium position $x_{0}$ at temperature $T$. The mass may oscillate in one dimension only for simplicity. We ...
Maximal Ideal's user avatar
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Precise relation between temperature change and physical quantities [duplicate]

I've learnt that many physical quantities like length or volume etc depend on the change in temperature and some proportionality constant as: $\Delta{L}=l\alpha\Delta{\theta}$. In our physics class, ...
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3 votes
3 answers
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How does the temperature of the condenser impact an air conditioner's energy usage?

Air conditioners have a condenser after the compressor, in the high pressure side of the system. I've found graphs that show the compressor takes less energy if the condenser is colder. That makes ...
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