# Tagged Questions

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

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### Mixed Gas Absorbtion

Consider a gas misture that contains two type of atom, A and B. The gas is in equilibrium at temperature $T$. If on the surface of the gas container there are M sites that can absorb an atom gas, and ...
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### Work done by an ideal gas expressed as change in potential energy of fluid

I get confused in problems where it is necessary to evaluate the work done by a gas that someway moves a mass. I'll make an example. Consider the tube containing mercury and an ideal gas in A (...
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### Work done on gas problem with movable set

I found two different version of an exercise where the work is considered in a different way. Consider a gas in a tank divided in two parts by a movable set. The set in $B$ is also movable. If a ...
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### What is the heat transfer ability from a specific temperature to a solid surface area that changes according to ambient temperature?

I am looking for a formula to find the efficiency of using $55^\circ$ ground water to prevent a concrete pad with dimension of 14' x 28' from falling below $25^\circ$ Fahrenheit during sub freezing ...
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### Water evaporation rate: temperature vs humidity

I have a hot tub which I keep at 100 degrees F, and the water has "a lot" of dissolved salts in it. If I leave it open, will it evaporate faster when it is hot and humid outside, or when it is cold ...
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### Canonical partition function and counting

That's a silly silly question, so my apologies, but in this moment I could not reach out! Let's have a system made of a particle reservoir $R$, and a subsystem $S$. The total particle number is $N$. ...
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### Starting from an expression of E(V) and P(V) for the Birch-Murnaghan's equation of state, is there a way of obtaining an expression for E(P)?

I have a function, an equation of state named the Birch-Murnaghan's equation of state, in which the Energy ( $E$ ) is a function of the Volume ($V$), where $E_{0}$, $V_{0}$, $B_{0}$ and $B_{0}^{'}$ ...
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### In heat conduction, what does it actually mean to be in the steady state?

I have read about the method of heat conduction and I have some questions related to this topic: If I consider a metal bar and supply heat in one end, the heat will flow through the bar and if I ...
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### Is information entropy the same as thermodynamic entropy?

Context In one of his most popular books Guards! Guards!, Terry Pratchett makes an entropy joke: Knowledge equals Power, which equals Energy, which equals Mass Pratchett is a fantasy comedian ...
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### Calculating the Total number of States for a microcanonical system

Please note before flagging, I do not need help solving as the math is simple algebra. Where I am lost is understanding what the math means and why/how it is applied. Problem 2.4 from Reif ...
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### How to find entropy production of opening the windows in the winter?

Every time you open the windows in the winter (to bring in healthy and fresh air), room's warm air goes to Atmosphere. How to find entropy production of opening the windows in the winter? where the ...
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### Which one is better at keeping you warm? [closed]

Does Glass feel warmer during winter when you keep your feet on it or Wood?
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### Heat Developed in a Resistor

What does the graph that represents the total heat developed from time t = 0 by a resistor carrying a steady current look like (where heat is on the y-axis and time is on the x-axis)? The answer ...
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### Heat Production in a Current Carrying Wire

The rate of heat production in a wire carrying an electric current is proportional to... The answer is meant to be current with a power (e.g. the square root of current, just current, current ...
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### Definition of heat that does not produce a cyclic argument?

If we are going to define (empirical) temperature from the zeroth law, we need a definition of heat that does not depend on the concept of temperature, else this would produce a cyclic argument. ...
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### How does hot air act in zero gravity?

In an environment with gravity, hot air is less dense than cool air, so it rises. How does hot air interact with cold air in a zero gravity environment, in terms of movement? Does it just stay where ...
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### Ohnesorge Number - why square root?

I understood the Weber number, but why would the Ohnesorge Number go like this: $$Oh = \frac{\text{viscous forces}}{\sqrt{\text{inertia \cdot surface tension}}}$$ Why the root? There seems to be no ...
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### Where does energy go in the death of the Universe?

So I thought that energy can't be destroyed or created but can only be transformed into another kind of energy. I read something about the Universe dying because all the stars will burn out and the ...
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### Liquid-vapor saturation curve

I am trying to draw the saturation curve for liquid-vapor region, but I don't have the exact equation. Can someone help?
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### Why hair dryer can heat up the air (kinetic and internal energies)?

The energy of an object is the sum of the kinetic and internal energies. When a hair dryer heat up its coils, it transfer energy to air molecule via radiation. My understand is that Kinetic Energy ...
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### Joule's “Work-Heat Equivalent” Experiment

I have been reading about the Joule's experiment that is supposed to have shown that work is the equivalent of heat. I can't really find the original paper and I am finding trouble understanding how ...
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### How to calculate the minimum kinetic energy required by a surface molecule to escape the liquid (during evaporation)?

Evaporation occurs when surface molecules have enough Kinetic Energy to escape the surface of the liquid. Given a certain volume of liquid at a certain temperature, is it possible to determine this ...
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### Does a reversible heat engine exchanging heat with an ideal gas that does a transformation imply that transformation is reversible?

Consider a reversible heat engine working between two sources. Suppose that one of the sources is a thermostat, while the other is an ideal gas which follows a transformation and exchanges some heat ...
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### If an isolated quantum system consists of only one particle, is it possible for it to be in a mixed state?

Mixed states are defined as the statistical ensemble of pure states. Classically, I understand the word, "statistical" referring to a system with a large number of microscopic particles. So if I go ...
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### A theoretical model for evaporation occurring when wind is blowing over the surface of water

I've recently done an experiment in which I was studying the variation of the cooling rate of hot water in a draft (wind). The air was blow directly over the surface of the water (kept in a ...
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### Confusion on meaning of fugacity in scientific publication

in my research project in statistical mechanics, in the context of phase transition and condensation, I was reading the seminal paper of Yang and Lee titled: "Statistical theory of equations of state ...
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### what is the physical significance of dielectric constant and loss tangent?

I want to know that the significance of dielectric constant and loss tangent behaviour. How it characterises the materials. and possible relation between the dielectric constant and polarisation ?
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### Entropy and Clausius inequality

From the Clausius inequality we can derive that the efficiency of a Carnot (reversible) cycle is given by: $$e= 1 - \frac{T_c}{T_h}$$ Is this true for every reversible cycle? Is the efficiency of all ...
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### Why can't "cold flow from an area of coldness to hotness? [duplicate]

Why do we always talk of heat flow from a hotter region to a coder region? Would it be wrong to say that cold flows from one place to another?
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### The Zero Electricity Air Cooler : How does it work? [duplicate]

I have seen from a video and a website where they said that, temperature can be reduced by reducing the area where the air passes. But what theory can explain it more precisely? I guess this could be ...
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### Average energy from Boltzmann energy distribution is not the same as average kinetic energy of an ideal gas:

The Boltzmann energy distribution represents the probability of a micro-state taking an energy E. It can be formulated as follows: P(E)=\frac{1}{kT}\cdot e^{-\frac{E}{kT}} \end{...
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### How do I calculate the amount of heat transfer to agitated air?

Suppose my room is x degrees C. The air in my AC ductwork is a constant y degrees C and is blowing at z m/s. We assume there is no heat transfer from the outside. How can I figure out how long it will ...
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### Why did this ice explode?

After watching this video of molten copper poured on a block of ice, the whole thing kinda exploded. What would cause ice to explode when subjected to molten copper?
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### Isochoric Kelvin Plank - Clausius Equivalence

As the Clausius statement is underpinned by the assumption that W=P.∆V Therefore ∆V=0 , W=0 Can anyone restate the Kelvin Plank-Clausius Equivalence Proof considering a solely Isochoric process ...
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### What VOLUME does exactly the $V$ term in ideal gas equation represent?

According to kinetic theory of gases 'the actual volume occupied by the gas molecules are negligible in comparison to the volume of the container.' I believe that this assumption is significant ...
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### Home Work Help: Calculating Entropy for Melting Ice - Clarification on answer

The question states: What is the change in entropy for the process to completely melt 8.0 kg of ice at 0°C? The formulas for Entropy we've been introduced to are: ...
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### Difference between KE “relativistic” mass and heat mass

I have been told in several answers that the term "relativistic mass" is no longer considered adequate wrt. the mass/energy increase in KE. Yet, I read that 1 Kg of gold's mass ingreases by 10^-14 Kg ...
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### How to convert relative humidity to humidity ratio [duplicate]

I wish to calculate the enthalpy of moist air using a formula which combines sensible and latent heat, specifically: $$h=h_a + x.h_w$$ where $x$ is the humidity ratio (mass/mass). However, I only ...
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### Confusion on electron volt and Kelvin?

If an element A has a binding energy of X eV with element B, can it be said that it is equivalent to X*11600K as 1 eV approx equals 11600K. I do not think this is correct as temp. is linked to the ...
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### Where does the free energy powering this device come from?

I encountered this problem in an IAP course at MIT back in 1971, presented by Prof Pritchard. You have a long tube, at one end of which is a semi-permeable membrane. This membrane allows water to ...
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### Entropy change in mixture of two gases

I'm confused about the entropy change if two gases, initially separated, are mixed togheter in a rigid box. I use the following \Delta S_1= n_1 c_{v,1} \mathrm{ln}( \frac{T_f}{T_{i,1}}) + n_1 R \...