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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In the Nernst equation $E=E_{cell}-\left(\frac{0.0592V}{n}\right)\log Q$, what does the $E_{cell}$ represent?

In the Nernst equation $$E=E_{Cell}-\left(\frac{0.0592V}{n}\right)\log Q$$ what does the $E_{cell}$ represent? I read that $E_{cell}$ is the standard state condition of the cell, let us say that we ...
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1answer
48 views

Entropy generation during irreversible adiabatic expansion

During irreversible adiabatic expansion entropy is generated. It means that the gas expands to as greater volume than that during reversible adiabatic expansion for the same change in pressure. How ...
4
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1answer
44 views

Is osmosis a kind of thermal machine?

The hyperphysics article defines osmosis as a process driven by internal energy and internal energy is defined as energy associated with random,disordered motion of molecules. Osmosis develops ...
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24 views

processes that cause heat loss in buildings [closed]

I'm looking for a fair study in which they assessed the importance of different processes that cause overall heat loss in buildings. With processes i mean convection, radiation, conduction trough the ...
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0answers
20 views

Ratio of Stagnation to Normal Flow Properties in Incompressible Flows

I know in compressible flows the ratio of stagnation to normal flow variables is a function of the Mach number and usually the specific heat ratio. Does this ratio mean anything for incompressible ...
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18 views

How does heat conduction differ from convection? [closed]

How does heat conduction differ from convection?
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36 views

Why does the temperature of the gas in a container moving with constant velocity not change?

Systematic changes do not affect thermodynamic equilibrium. What does this mean? And what kind of systematic changes are allowed? The container with gas is stationary till some time then it's ...
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48 views

How to see intuitively that $\kappa_T$ is constant for solids?

In thermodynamics we define $$\kappa_T = -\dfrac{1}{V}\left(\dfrac{\partial V}{\partial p}\right)_T.$$ By this definition, if we are treating $V$ as a function of $p$ and $T$, then $\kappa_T$ is ...
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54 views

Water vs. Air : Heat Absorption/Capacity

I am not a physicist by any means and not even a current student, but nonetheless I am looking for an answer. Here is what I have gotten so far from university websites and other various resources on ...
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72 views

Might the zero point of the Kelvin scale been mislocated? [closed]

This is fundamentally a thermodynamics question, but it has ties to cosmology and the temperature of the cosmic microwave background (cmb). Since T(cmb) ~ 2.725 K it brings up a comparison with the ...
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16 views

the physics of absorbing a laser's beam through contact of mirrors [closed]

If you were to set out multiple mirrors or even double sided mirrors how many Times would it have to reflect to be completely absorbed into heat by the lasers??
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1answer
30 views

The effects of heat and work on a system

I am unable to grasp the following statements which I found in the literature. For a closed system (no transfer of matter), heat in statistical mechanics is the energy transfer associated with a ...
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35 views

Energy dissipation in spinning wheel

I was given the following question in a test. A spinning wheel A is brought in contact with an identical wheel spinning at identical speed.The wheels slow down under the action of friction.Which ...
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2answers
55 views

Difference between two types of pressure

When I first studied thermodynamics the concept of pressure was defined by means of the fundamental relation $S = S(U,V,N)$ for simple systems. The pressure was thus defined by $$P = ...
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45 views

Is it possible to consider PV diagrams without the equations of state?

Suppose that we have the equations of state for a particular system, or equivalently, that we have the fundamental relation $S = S(U,V,N)$. If we want to write down a PV diagram it will be quite ...
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1answer
65 views

Would it be possible that a broken glass can return to its original state spontaneous at 0K?

my teacher said that a broken glass can't fix itself spontaneous because of the second law of thermodynamics, entropy won't decrease in a isolated system. But when the temperature is at 0k, then ...
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14 views

Temperature of throttled flow

In a pipe with a throat, closed off to the left, I'm pouring in $\dot{n}$ atoms per second from the left. These atoms combine and do a chemical reaction, which releases energy. To the right, past the ...
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1answer
23 views

Velocity of flue gas

I was wondering on how to calculate velocity of a flue gas which has a gas molecular weight of 28.1544, density of 0.0268 (lb/ft$^3$), temperature of 980˚F, specific heat of 0.2805 (Btu/lb-F), and ...
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1answer
40 views

Density solver for ideal mixture of real gases

I am referring the paper on GERG-2008 equation of state. I am interested in calculating the properties of ideal mixtures of real gases. The GERG-2008 EOS is in Helmholtz free energy and hence the ...
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2answers
49 views

Why are metals worse conductors when heated?

When metals, (such as in circuits), are heated, their ability to conduct electric current is hampered. Why is this? Does the transition towards liquid disrupt a metal's ability to conduct, or is ...
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59 views

In enthalpy, is PV the pressure energy?

In the case of a fluid, does the $PV$ contribution to the enthalpy correspond to the pressure energy in fluid mechanics? (Related: What is Pressure Energy?)
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Is this thought experiment violating the the Second Law of Thermodynamics?

There is an adiabatic box, with a board in the middle, which is adiabatic too.The board separates the box into two parts and there is a small hole in it, which is close to a coil and the hole has a ...
3
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1answer
36 views

Pointwise temperature and Thermodynamic Temperature

When I studied Thermodynamics the definition of temperature I've learned (based on the Gibbs' postulates) was: $$T = \dfrac{\partial U}{\partial S}.$$ This quantity has all the properties of the ...
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37 views

why water can exist in both liquid and vapour state at critical point?

Water can exist in both liquid and vapour state simultaneously at 22,055 MPa and 373°c. why in these conditions water exist in both states. How can we know whether water is in liquid state or in ...
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1answer
21 views

Heat capacity at constant volume and internal energy

I read that heat supplied at constant volume to a system containing ideal gas changes the internal energy of system, i.e $q=nC_v\Delta T=\delta U$ But what happens if I heat a system and change its ...
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33 views

Justification of the State Postulate

I have just started thermodynamics (not with statistical approach but with macroscopic approach), in which the state postulate reads Only two independent intensive properties of a simple ...
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31 views

Isentropic flow through nozzle

I've a question concerning the use of the Bernoulli principle. Let's say I have a pipe filled with air at atmospheric pressure, with a constricting section ala the figure below. The volume before the ...
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1answer
61 views

What is more important, energy or entropy? [closed]

What decides if something will change or remain the same? Energy or entropy considerations?
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1answer
93 views

Why do we need the Zeroth Law of Thermodynamics?

I have just recently started learning some very basic thermodynamics and there is one question that has been driving me crazy: Why do we even need the Zeroth law of thermodynamics? The law ...
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31 views

Finned Surface (Corrected Length)

I have to analyze a rectangular convective tip and determine a few factors. Then I have to use the corrected length (Lc) approach and calculate the same factors. My issue is with the formula for ...
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25 views

Thermodynamic equilibrium or thermal equilibrium and equipartition theorem

In all derivations of the equipartition theorem I can find a thermodynamic equilibrium distribution is used to show it's validity. But more vague sources (this site, wikipedia) state that only ...
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1answer
53 views

Does heat flow through a rod with a uniform current?

Consider a rod with uniform current flowing through it from left to right. Will heat flow throughout the rod or will the rod heat up uniformly? My thoughts are that no heat will flow, but rather the ...
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1answer
57 views

Why is entropy of system same for reversible and irreversible processes? [closed]

I read that entropy change of universe is zero in a reversible process but positive in a irreversible process,then doesn't it mean that entropy change of system of both the processes must be ...
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0answers
32 views

Meaning of $\frac{1}{\beta} \frac{\partial \ln{Z}}{\partial X}$ in arbitrary ensembles with X being a sharp Observable of the System

I often find the statement, that for an arbitrary ensemble with Observables $O_i$ of which only the mean value is known, and $\tilde{O}_j$ that are known exactly, the partition function ...
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1answer
25 views

Characteristics of a Particle reservoir

What does a particle reservoir mean in thermodynamics? How is it characterised? Heat reservoir for example, is characterised by temperature and supplies or absorbs any amount of heat without changing ...
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17 views

Black Body Radiation of a Home

If there is a home which is far away from all other buildings, what is the heat transfer due to radiation at night? Is the governing equation this: sigma*(T_home^4 - T_space^4)? Does the home radiate ...
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2answers
176 views

Why are sound waves adiabatic?

I want to know why we can treat sound waves as an adiabatic process. Precisely, I know that pressure and density vibrations occur so fast that molecules have no time to exchange energy (I might be ...
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0answers
43 views

Boiling Water in the Vacuum of Space [duplicate]

In space: When you depressurize ice with a temperature of -72 degrees Celsius would it turn into water? Is there a stable temperature range in which water stays liquid? Does the temperature ...
3
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1answer
41 views

Difference between state variable and state function in thermodynamic?

I think these two terms are sometimes used as synonyms and other times as different concepts. Can some explain what is the difference? An example would be good. Also, can state variable be the state ...
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2answers
71 views

Free expansion of an ideal gas

I am having trouble understanding the transient phase of an ideal gas expanding into vacuum. Firstly, the pressure of any gas is defined only when there is an instrument (barometer/ wall/ piston) ...
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2answers
122 views

1st Law of thermodynamics (conservation of energy) and quantum tunneling

Doesn't quantum tunneling contradict the 1st Law of thermodynamics? As far as I remember my school physics teacher told us that quantum tunneling is the reason why we can observe the alpha decay, as ...
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56 views

How to solve PV questions? [closed]

A diatomic gas is expanded according to $PV^{1.3} = constant$. Hence choose the incorrect statement Gas cools at expansion Work done by surrounding is negative Gas expands by absorption of heat from ...
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1answer
30 views

Water molecule Resonant Frequency

If water is subjected to microwave energy at the water's exact resonant frequency but 90 degrees out of phase, would the water molecule cease vibrating? Would the water then freeze or be cooled at ...
2
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1answer
30 views

No heat flow is to thermal equilbrium as … is to mechanical equilbrium?

When two systems are in thermal equilibrium, this means that there is no heat flow between them. What is the analogous definition for mechanical equilibrium? (I know that in mechanical equilibrium ...
0
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1answer
42 views

Conterflow heat exchanger with different flow rates

If we have tube in tube heat exchanger, in classic situation surface area in contact with both fluids is the same (if we ignore wall thickness of the tube). If fluids have significantly different ...
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1answer
37 views

Lead shielding very close to the Sun

I understand that eventually lead would melt when it nears the sun. In a liquid state how effective would lead be in blocking radiation? Would it still be as effective as solid state of lead? What ...
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1answer
41 views

How should I think of a liquid in terms of interatomic potential and molecular speed?

A rather simple question for liquids specialists I guess but I have hard time finding information about this. Here is my problem. I understand the ideal gas theory and the Maxwell's speed ...
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1answer
28 views

Adibatic process in QM and thermodynamics?

I have come over the phrase 'Adiabatic process' in two different contexts, that of QM and Thermodynamics . QM A adiabatic process is one is slow compared to: $$t=\frac{\hbar}{E_n-E_m}$$ and ...
2
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1answer
57 views

What does the solid phase in a two-dimensional system with Lennard-Jones potential look like?

Consider a system of two dimensional particles interacting via Lennard-Jones pair potential: $$u(r) = 4[(\frac{1}{r^{12}})-(\frac{1}{r^{6}})]$$ where r is the distance between two particles. What does ...
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2answers
59 views

How to conceptually identify reversible and irreversible processes?

When I studied thermodynamics for the first time I didn't really get much the conceptual understanding on reversibility, but nonetheless I've got a rough understanding and a mathematical criterion for ...