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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What about the grand canonical ensemble allows you to use it to describe quantum gases as compared to the canonical ensemble?

Probably an obvious question but this is my understanding so far: Ideal classical gas - gas where occupancy of an SPS <<1. Ideal quantum gas - cold dense gas where occupancy of SPS can be ...
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Increasing thermal efficiency in cooking pasta

Odd question, I know, please don't bash me. Hopefully somebody can help me get a better understanding on this matter. Pasta is usually cooked by dropping it in boiling water (either salting water to ...
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What are intuitive definitions of the 4 thermodynamic potentials?

So out of the 4 thermodynamic potentials only the internal energy seem to make intuitive sense to me. My understanding of enthalpy is that it is a state function which represents the total heat ...
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What is meant by the temperature of an atom? [duplicate]

Does it make sense to ask 'what is the temperature of an atom?'. Why not?
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Ideal gas cycle efficiency in $p$-$H$ diagram [closed]

We have a thermodynamic cycle of an ideal gas in a $p$-$H$ (pressure-enthalpy) diagram with known temperature $T_{1}, T_{3}$ and pressure $p_{1}, p_{3}$ (see the picture below). What is the ...
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Confusion with work done in isochoric process

So recently I've come up with this thought In an isochoric process, many books state that the work done is zero because there is no change in volume i.e. the gas isn't expanding nor it is contracting....
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How long will it take for a Schwarzchild Planck mass BH to evaporate? [closed]

My late-night calculations for the question "how long will it take for a Schwarzchild Planck mass BH to evaporate" predict 4.7 septillion years. I'm sceptical. Are my calculations true, according to ...
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About Feynman's treatment of entropy

Feynman said in this chapter that if a system absorbs (rejects) an amount of heat $d Q$ at a temperature $T$, then we say the entropy of the system increased (decreased) by an amount $dS=d Q /T$. And ...
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Conceptual block on energy transfer [closed]

I recently posted a question about energy transfer in oblique elastic collisions between equal mass balls, asking how much energy the slower ball can transfer to the faster ball. The correct answer ...
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Use of the solid angle in deriving the Maxwell-Boltzmann distribution

This is from a course in statistical mechanics, specifically the derivation of the Maxwell-Boltzmann distribution. We have an integral over the momentum space $$Z = \frac{V}{(2\pi \hbar )^3}\int d^3p ...
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Function Of A Constant Volume Gas Thermometer

Concerning the mechanism of a constant volume gas thermometer, I was wondering how the adjustment of the second tube upon the open side increases the pressure; specifically, I possess knowledge of how ...
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reverse osmosis membrane

We are second year cram schoolers , we are currently working on a project tackling water desalination by reverse osmosis and are required to do an experience. During the process, we encountered some ...
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Can regular air conditioner be used as heater? [closed]

In winter season, the normal room temperature is generally 6 to 10 degree Celsius, if the air conditioner is working at 25 degree Celsius will it be working as a heater, making the room warm (relative ...
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Surface temperature variation with distance [closed]

So here is the question I'm troubling with: We estimate that the temperature varies approximatively with that relation: $$T(x,y)=T_0+\Delta T_0\mathrm e^{-\oslash(x,y)}$$ Where $\oslash(...
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Query about maximum temperature you can raise a block in an isolated system of 3 blocks [closed]

Set up: Consider an isolated system of 3 blocks: 1,2 and 3. At temperatures 100K , 300K and 300K respectively. The blocks all have identical properties other than temperature, i.e specific heat ...
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Does vapor latent heat depend on temperature? [duplicate]

Adding energy to water makes it's temperature increase. This continues until it reaches 100 °C (at 1 atm) when it turns to vapor with a vaporization energy of 2257 kJ/kg. But if we lower the pressure ...
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After I pour a cup of tea, I can't drink it for 10 minutes. Will it stay warmer if I add the milk at the start, at the end or does it not matter? [duplicate]

So preface, I work in engineering so I'm familiar with the basic principals of most fields in physics, but specialise in Civil Engineering so my knowledge of thermal physics is poor and I haven't ...
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Second-order partial derivative of Helmholtz Potential

So the lecture notes to my thermodynamics course contain this relation: $$\left(\frac{\partial^2F}{\partial T^2}\right)_{V,N}=-\frac{1}{\frac{\partial^2U}{\partial S^2}}$$ With no further explanation ...
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The first law of Thermodynamic in curved space

As we know, the first law of thermodynamic is $ dE=TdS-PdV+\mu dN $. is it true for a generic metric? what is the covariant form of this equation? for example, I think chemical potential and number ...
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Grunesian Parameter vs. Effective Debye Temperature

Both the grunesian parameter and "effective" debye temperature account for changes in lattice due to thermal expansion. Does this mean both can be used interchangeably? In other words, If I use an "...
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Can anyone give python code to solve TOV equation? [closed]

an anyone give python code to solve TOV equation?
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2answers
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When we push on a wall, can we say work is being done on the atomic particles in contact with our hand?

Since textbooks say work is act transfer of energy, it led me to think of the following assumption: Work is being done on the the atoms in the wall, in contact with the hands, when we push (hard) ...
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Sun as a black body [closed]

consider the sun as a black body in 6000'Kelvin and Diameter of 1.4 *10^9 meter .which is 1.5*10^5 meter far away from the earth. a)find the Irradiance on the earth's surface. b)if the earth's ...
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Entropy increase after the Big Bang?

I'm trying to understand the increase of entropy just after the big bang. The way i see it going from a "soup" of particles to organized and ordered sytems like solar system, galaxies and clouster of ...
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Acoustic velocity of ideal Boltzman, Bose and Fermi gasses [closed]

compare the acoustic velocity of Maxwell_Boltzman and Fermi_Dirac and Bose_ Einstein ideal gasses. this is our home work for statistical mechanics and we are studing the book of Pathria the 7th ...
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Vacuum as blackhole supersolid? [closed]

If the vacuum is a super-fluid, would the infinite vacuum energy that is nonphysical to us come into play thus making all portions of the background have infinite energy at initial expansion? So Would ...
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1answer
51 views

Restricted thermal expansion [closed]

Imagine a metal rod of length $l$ with mass $m$. How would it expand upon a temperature difference of $\Delta\vartheta$ with an expansion coefficient of $\alpha$ when there are two forces $F_1$ and $...
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What is a condensate/ the act of condensating?

We talked about the Bose-Einstein-Condensate (BEC) in our thermodynamics lecture and are discussing superconductivity in the condensed matter lecture where we also talked about a condensate ...
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Determination of the thermal resistance of a molding tool with cooling channel

This is a section of cooling channels in injection moulding tools. I have tried to calculate the thermal resistance in this section with 2 methods, one analytical and one numerical. analytical ...
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2answers
70 views

Which one is more efficient: a heater or a cooler?

I know that in an ideal case, both a heater and a cooler would be Carnot engines. Assuming that the magnitude of temperature difference across them is the same, they would have the same efficiency. ...
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Is there a net increase of temperature in thermal equilibrium? [closed]

If I have two objects sitting side by side let's say a water pump running at 10 degrees c and a processor running at 50 degrees c. The heat transfers from the hotter to the colder object until they ...
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38 views

First and second laws of thermodynamics: getting increments from inexact differentials

First law of thermodynamics states that $$\tag{1} dU=\delta Q + \delta W$$ whereas second law of thermodynamics states that, for a reversible process, $$\tag{2} dS= \frac{\delta Q}{T} $$ I have ...
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Energy of moving particles [closed]

When particles move through a space with a certain velocity, which kinds of energy do they have? They should have translational energy because of their motion, right? But do they also have sensible ...
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What is the work energy theorem?

Work energy theorem is one of the fundamental theorem in physics. Simply it is a relation between work and kinetic energy of a body. Then a question arises that what is the work energy theorem is all ...
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Is it possible to estimate the composition of a mixture between ice and liquid water from a temperature heat graph? [closed]

I'm confused whether the equation for thermal equilibrium can be used to obtain the composition of a mixture with only having as information a graph. This happened when I attempted to solve a problem ...
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Validity of equipartition theorem and choice of coordinate axis

While reading through the basic derivation of how kinetic energy is related to temperature, I stumbled upon equipartition theorem where $\frac{1}{2}mv^2 = \frac{1}{2}kT$ thus $\frac{3}{2}kT$ in 3-...
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2nd law of thermodynamics violation? [duplicate]

What if I assume an ideal gas in a cylinder having frictionless piston and perfectly insulated walls with a perfectly conducting base is kept on a reservoir at temperature $T$ which is greater than ...
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1answer
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The reversible Carnot cycle is the most efficient between $T_2$ and $T_1$. Is it a form the second law itself?

The second law of thermodynamics proposed by Clausius, Kelvin, Carnot ..etc in its original form as T dS> dQ for irreversible process and Tds =dQ only for reversible thermodynamics process. This ...
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Apparent contradiction concerning the net work of a Carnot cycle

The net work of a Carnot cycle, $W$, is $$\tag{1}W=Q_{h}-Q_c.$$ This work also satisfies $$\tag{2}W=Q_{h}\bigg ( 1-\frac{T_c}{T_h} \bigg )$$ Let us fix $Q_{h}$, the amount of heat initially ...
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Deriving $Q_{1}-Q_{2}=W$ for a perfect gas that had gone through a Carnot cycle

I saw multiple times that if an engine, say Carnot engine, absorbs heat $Q_{1}$ at $T_{1}$, does work $W$, and expels heat $Q_{2}$ at $T_{2}$, then we should have$$\tag{1}Q_{1}-Q_{2}=W.$$ Let us say ...
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Thermodynamic Equilibrium math. characterisation $d P=0$ question

I have a basical question on the mathematical condition characterizing a system beeing in thermodynamic equilibrium: Let $P(A, B, C)$ is a thermodynamic potential with natural variables $A, B, C$ ...
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Understanding that kelvins statement of the second law

I am having a bit of trouble understanding the inequality given below: Fig 13.10(b): I am guessing that it looks as though all the heat in is going to do work, hence the violation (although I cant ...
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thermal expansion and thermodynamics (a brass plate) [closed]

A bolt hole in a brass plate has a diameter of 1.200 cm at 20°C. What is the diameter of the hole when the plate is heated to 220°C?
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Why must all natural processes be irreversible?

My thermodynamics lecturer was talking about reversibility and the idea of spontaneous change and he mentioned that all natural processes are irreversible. Can someone offer some sort of proof or ...
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Pressure and volume [closed]

Currently, I am working on this experiment where I hit a balloon with a small object so that the pressure inside a balloon changes. The pressure increased when I hit the balloon, but I need to ...
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Work done in an irreversible adiabatic process [closed]

This is a problem I encountered while solving SS Krotov. A vertical thermally insulated cylinder of volume V contains n moles of an ideal monoatomic gas under a weightless piston. A load of mass M ...
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Would a group of molecules in a container, settle down after a long time? (considering that no gravity acts on them) [duplicate]

Because, every time they collide, don't they emit radiation? As in, losing energy in the form of this radiation, So eventually, won't they lose all of their kinetic energy? Of course the time taken ...
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Thermal diffusity. What do I use? [closed]

I'm not a physics expert. Actually don't know much at all but I'm trying to find an answer to a problem. If I had a silicone (or clear vinyl if more appropriate) tube with .25 inch interior ...
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2answers
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When to use emissivity in Stefan-Boltzmann Law?

In Stefan-Boltzmann Law: $$q=σAe(T_1^4−T_2^4)$$ I sometimes see it written with emissivity, $e$ and sometimes without. How do you know whether to include it? I know $e=1$ for an ideal radiator and ...
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On the way adiabatic processes were defined in Blundell's Concepts in Thermal Physics

In Blundell's Concepts in Thermal Physics, page $117$, the author defines an adiabatic expansion as follows, The word adiathermal means ‘without flow of heat’. A system bounded by adiathermal walls ...