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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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Why is chemical potential constant for the system in Gibbs distribution?

Consider the grand canonical Gibbs distribution where a system is in thermal and diffusive equilibrium with a large reservoir. The system can take on different energies $E_i$ and contain different ...
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Difference classical and statistical thermodynamics

What should I read to link between classical thermodynamics or engineerig thermodynamics and statistical mechanics?
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Transfer of heat in relativity and conservation of momentum

In relativity momentum is associated with flux of energy (not just mass), e.g. for a single particle $\textbf{p} = (E/c^2)\textbf{v}$ Imagine a rod which initially is hotter on one end. If the rod is ...
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Total energy of a gas in an external magnetic field

Given the grand thermodynamical potential $\Omega$, the particle density $N$, the chemical potential $\mu$, the temperature $T$ and the entropy $S$, one can compute the total energy by the well known ...
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PV diagram of pure substance

Why does the specific volume of saturated solid state of water decreases with increasing pressure and the specific volume of saturated liquid wrt vaporisation increases with pressure? Can anyone ...
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Proportionality between pressure, volume, and number of microstates for an ideal gas?

I'm pretty new to Thermodynamics, but I've been playing around with some different computations to reinforce my understanding. I came across the result $$\Omega \propto \left( PV^\gamma \right)^{fN/2},...
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Calculating rate of change of thermal energy and applying that to usage in calculating the time it takes to reach equilibrium

So if I have an experiment with two gases that are identical and have a specific heat of 100 j/(KM) and there is a divider in between the gases with a surface area of 1 square meter, and a thickness ...
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141 views

What mechanism at the microscopic level determines whether a system heats up or not?

When placed in an ordinary or a microwave oven, a beaker of water heats up except during boiling (i.e., a phase change involving latent heat). Now, suppose a system absorbs energy in such a way that ...
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Is entropy generation in a process equal to change in entropy of universe?

I read on a source that both quantities are equal ,then why are they specified differently? Can we directly find entropy generation in any process just by calculating the entropy change of universe?
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Why do bubbles initially stick to the side or the bottom of a glass while boiling?

When boiling water, I've noticed that bubbles will appear to grow at the bottom of the glass for a period of time and then rise. I've read that bubbles form from nucleation centers but I don't know ...
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107 views

If irreversible process is quasistatic then can we find it's work using $pdv$ formula?

Now it's given on Wikipedia that quasistatic process can be irreversible,so can I find the work done by the closed system undergoing a process using $pdv$ work?...Next, is that work less than the ...
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Why does a lot of water vapour come suddenly after the heat source of boiling water is removed? [duplicate]

I have noticed this several times. When I am boiling water, a few seconds before its boiling point, vapours are formed as usual. But if I turn the gas off before boiling, the moment it turns off, I ...
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Why $(\frac{\partial S}{\partial T})_P=(\frac{\partial S}{\partial T})_V+(\frac{\partial S}{\partial V})_T(\frac{\partial V}{\partial T})_P$?

In the thermodynamics book (Adkins) I'm using, the following relation is cited without reference but I am not sure where it comes from. $$\left(\frac{\partial S}{\partial T}\right)_P=\left(\frac{\...
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Pinch point for heat and mass exchanger devices (like cooling towers)

As you know, there is a pinch point for heat exchangers... But can we introduce a pinch point for heat and mass exchanger devices (like cooling towers)? At cooling towers, the outlet water ...
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3answers
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How can I show this process was cyclic?

For a general thermodynamic system, it is always possible to directly control its extensive variables discounting the entropy. For fluids, this is usually just the volume of the container. Say we have ...
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Does the amount/speed a balloon rises vary with the temperature of the gas inside, given a constant type and amount of gas?

I'm attempting to conduct an experiment with a balloon. I fill it up with some amount of helium. If I cool the balloon down (say with liquid nitrogen), the balloon's volume will decrease (because of ...
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2answers
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Applying Bernoulli's equation in fully developed viscous pipe flow

Can we apply the inviscid Bernoulli equation $$ \frac{P}{\rho} + \frac{1}{2}V^2 + gz = constant$$ along the center line of a fully developed pipe flow? I think we can since the shear stress along ...
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1answer
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Bekenstein Bound and frame of reference

According to Wikipedia, this is the formula for the Bekenstein bound $$ S \le \frac{2\pi k RE}{\hbar c}$$ where $E$ is the total mass-energy. That seems to imply that the presence of a black hole in ...
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What limits how hot can a macroscopic object be heated by conventional means?

What I mean by conventional, is that chemical, mechanical and electromagnetic heating are in bounds, but not nuclear. And I assume that there a limit to how much a material can be heated due to: The ...
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1answer
44 views

Joule expansion and center of mass

This question comes from a doubt resulting from some physics forums. Similar to and related to this question, I have a doubt on Joule expansion raised by reading too much bad faith arguments. I'm not ...
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Molar Heat capacities

Molar Heat capacity is defined as the amount of heat required to raise the temperature of one mole of a substance by unit amount. As my textbook mentions the molar heat capacity of an ideal gas ...
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1answer
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Gas molecules / photons interaction

I've encountered a comment on a Physics SE post: ... there are no perfectly elastic collisions between atoms and molecules. Some part of the energy/momentum will be converted into photons... My ...
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Can $PV^\gamma$ be treated as an entropy function?

In a reversible adiabatic process, $PV^\gamma=\text{const.}$ but reversible adiabat $\iff$ isentrope so does that mean $PV^\gamma$ can be treated as a function for entropy?
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Evaporation and boiling

I recently read that evaporation takes place on the surface of the liquid and boiling takes place throughout the liquid. The part about evaporation seemed legit as it is observed in nature that water ...
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Air pressure problem solving with Boltzmann factor

I am talking about the very classical thermodynamics problem, where you are given a cylinder of length $D$. The cylinder is being rotated with one of the sides as axis. You're given the pressure in ...
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Fluid dynamics - boundary later equation $f'''+ff''-f'^2+\theta = 0$ and $\theta''+Prf\theta' = 0$

Our lecturer gave us a system of boundary layer equations: $$\begin{align}f'''+ff''-f'^2+\theta &= 0 \\ \theta''+Prf\theta'&=0 \end{align}$$ subject to boundary conditions: $$f=f'=0, \...
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Why are diamonds formed under high pressure? (use entropy)

My book asks how can diamond ever be more stable than graphite, when it has less entropy. I have to explain how at high pressures the conversion of graphite to diamond can increase the total entropy ...
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Deduce if path is adiabatic from the state space

Can we deduce, for quasistatic processes, if a process is adiabatic by purely looking at its path in state space? Take, for example, the process of stirring a liquid to heat it up (adiabatic) and ...
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1answer
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Grand free energy as force towards equilibrium

My book on thermal physics shows that, for a system in thermal and diffusive equilibrium (with a reservoir that can supply both energy and particles), the grand free energy, $\Phi$, tends to decrease. ...
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57 views

How to calculate work for irreversible adiabatic processes?

By the first law, we know $\text{d}U=\delta Q+\delta W$ and, on adiabats, we know $\text{d} U=\delta W$. But what is $\delta W$ for irreversible adiabatic processes? Take a thermally isolated ...
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Book on heat generated in a circuit

Can someone suggest me a book with tough quality questions on heat generated in a circuit like in rc,lr circuits etc.
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Latent heat and and raising temperature [closed]

So in first order phase order transitions, the parcel of matter undergoing the phase change can release energy into its surroundings. However it is "latent" in so far it will not raise the temperature ...
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Physical Model for a Black Body

I am learning about black body radiation and it was stated in a textbook that The best model for a black body is a large cavity with a very small hole in it which absorbs all incident radiation. ...
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1answer
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First order phase transition and latent heat

Usually in physics, first order phase transitions are phase transitions where the free energy potential's first derivative is discontinuous when differentiated by some thermodynamic variable such as ...
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How does temperature affect the elasticity and spring constant of a rubber band

Rubber bands expand when chilled and contract when heated (no stretching, just when heated/chilled and at rest) to my knowledge. Why are hot rubber bands able to be stretched longer than cold rubber ...
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1answer
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The minimum temperature that water can reach at a cooling tower

I have read this sentences at a paper and I can't understand the reason: Consider a cooling tower and read the following sentence: "When the water enters hotter than the air, the ideal condition ...
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1answer
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Why Gibbs energy for nucleation theory?

In nucleation theory, the free energy is given by (https://en.wikipedia.org/wiki/Classical_nucleation_theory but in many other places also): $$\Delta G=\frac{4\pi }{3}r^3\Delta g +4\pi r^2\sigma,$$ ...
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Placement of warm inlet vs cool outlet for best water cooling design

I am conducting a small trial and have a reservoir and coils inside running refrigerant. The coils are to cool the water. I will have warm water coming into the reservoir and chilled water going out. ...
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Finding temperature at junction of rods

Let's say I have three tubs, from left to right Tub 1, Tub 2, Tub 3. Tubs 1 and 3 are at 50 degrees Celsius and Tub 2 is at 10 degrees Celsius. Tubs 1 and 2 are connected by a copper rod, and tubs 2 ...
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What model should I take for fluid flow with bubbles, in pipe?

We try to combine model with experiment(already done). What model should we take do draw thermomap of pipe? What laboratory can we ask? Thanks..
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What's the problem with Black Hole evaporation?

Black hole evaporation is not unitary because it takes a pure state to a mixed state. On the other hand, ordinary decay processes in Quantum Mechanics do not seem very unitary either. (For example, if ...
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1answer
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How much heat to dissipate to lower temperature of steam?

Given 100g of steam at 150 degrees, how much heat will you have to absorb from the system to have 100g of ice as a result? I know that we need m * q * dT kJ to ...
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Work definition does not make any sense for coherent states? TPM (two projective measurement) scheme

I'm talking about the relation that if we are in a isolated, quantum system that only allows for work exchange with the surrounding system we know from the first law of thermodynamics that $\Delta E = ...
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Is there a difference in the infrared absorption spectrum of a greenhouse gas when pure and when mixed with non-greenhouse gases?

According to the standard IPCC greenhouse climate change hypothesis a doubling of the preindustrial CO2 concentration of 285 ppm in the atmosphere - the current value is 405 ppm - would lead to an ...
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Dimension of an Exponential with Dimension

My thermodynamics professor gives a formula for ideal gas like this: $$s _ { 2 } - s _ { 1 } = c _ \mathrm{ v , a v g } \ln \frac { T _ { 2 } } { T _ { 1 } } + R \ln \frac { v _ { 2 } } { v _ { 1 } }.$...
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Temperature / heat transfer through multiple layers of insulation materials

how can I determine the resultant temperature on one side of a wall after a specified time when the wall has a series of different insulation layers and when the temperature on the other side is known,...
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Water and air temperature

Does the theory hold that if I blow warm air into a pool through tubing on the bottom it will raise the temperature of the water?
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Is rust a good thermal insulator as opposed to bare steel or hardened clay?

I have no idea if this is the correct site to find an answer on this topic but considering it's a question of physical interactions I wanna give it a shot. I am in no way a physicist, just a hobbyist ...
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1answer
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Intuitive understanding of the derivation of the Rayleigh-Jeans law

I know the Rayleigh-Jeans law and how the formula predicts UV catastrophe. Without getting into the exact derivation, I am trying to get some intuitive understanding of it by using some of the broad ...
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1answer
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Increase Air Speed at outlet

I have a set up that inflates a rubber jacket in order release the metallic rings from underneath it. I am currently having issues with not having enough pressure (force) at the outlet to inflate the ...