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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64 views

Is zero heat capacity possible without violating the third law of thermodynamics?

Suppose we have a gapped system i.e. no gapless excitation is possible. If the thermal energy is insufficient to excite atoms from ground state to excited state of any kind (of a single atom or of a ...
6
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5answers
420 views

What is the difference between heat and light?

What i know is that light is an electromagnetic wave. Is heat also an electromagnetic wave of certain wavelength other than light ? Why the light wave cause heat in an object when it falls on the ...
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4answers
4k views

How does the Eco-Cooler air conditioner really work?

This article describes a device for developing countries which apparently cools the air by 5 °C without electricity. According to its YouTube video, it works by lowering the pressure to drag in the ...
2
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1answer
28 views

Derivation of Apparent Expansion of Liquid

The formula for apparent expansion of liquid in a container is given as follows: $$\triangle V=V_0{(\gamma_{l}-\gamma_{c}})\triangle T$$ Where $V_0$ is the volume of the liquid as well as the ...
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1answer
40 views

What's the minimum time scale for a candle to be lit in order for it to establish a steady state?

My Understanding When a candle is lit initially, it goes through a few stages (see, e.g. this explanation from the National Candle Association): Wick burns. Crusted wax on wick melts, evaporates ...
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1answer
39 views

Cooling power of CO2 being released from a gas bottle

I need help in calculating how much a constant flow of CO2, being released into a small pipeline from a pressurised gas bottle, cools down the pipeline (in watts), to figure out if I'd need to heat up ...
0
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1answer
39 views

Thermodynamics compression work [closed]

So I have a college homework problem that I have not been able to solve "A 4-L rigid rank contains 2 kg of saturated liquid-vapor mixture of water at 50 degrees celsius. The water is now slowly ...
0
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0answers
37 views

What is a solid strong material that DON'T absorb heat well?

I need to find a material that is very durable that don't absorb heat well even if its in a place that has a very high temperature ( Maybe 300° - 400° ) I understand its going to absorb heat but I am ...
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3answers
65 views

2nd law of thermodynamics' violation?

According to 2nd law of thermodynamics, it is not possible to convert heat 100% into work. Well, investigating about the Carnot Cycle, I have found out that in the first step, the process is to heat ...
6
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4answers
155 views

Physics of heating a swimming pool

This is motivated by a practical problem, but it's the pure physics that really puzzles me. My pool is heated via a heat exchanger. Water from the boiler enters the heat exchanger through (let's ...
4
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1answer
70 views

The Correct Statement of the Third Law of Thermodynamics

The Third Law of Thermodynamics can be stated in various ways, one of which is: The entropy of a perfect crystal at absolute zero is exactly equal to zero. Is this true for only "perfect ...
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0answers
30 views

How can one calculate the drop in air temperature associated with a rise in its humidity?

Background: I wish to model the effect of an evaporative cooling system in a humid, tropical environment to be used as a feasibility study. Anecdotally, such a system would be ineffective, but I would ...
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2answers
38 views

Motion of molecules of an ideal gas

Why does an ideal gas show only translatory motion and not vibratory motion?
3
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1answer
32 views

What are the effects of compositional changes in a thermocouple's junction?

We use thermocouples (type B) to measure the temperature of metals (Fe, Ag, Pd, etc) in a furnace under pressure. We weld two thermocouple wires together using an arc welder. This junction then comes ...
0
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0answers
28 views

What is the relationship between an expanding universe, an increase in entropy and the the creation of mass?

What is the relationship between an expanding universe, an increase in entropy and the the creation of mass? Could the creation of mass be driven by or in equilibrium with the creation of space?
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2answers
36 views

Effect on increasing pressure of boiler in an ideal Rankine cycle

In an ideal Rankine cycle with fixed inlet turbine temperature and condenser pressure, then what will happen to the heat supplied if the boiler pressure is increased? TRIAL My assumptions were that ...
4
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4answers
111 views

Conservation of Energy vs Expansion of Space

My question pertains to a possible inconsistency between the first law of thermodynamics and the general expansion of space itself. First, the knowns: Space itself has, and continues to expand - ...
2
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2answers
95 views

Why Boltzmann Entropy's formula is $k_B\log\ W$ and not $0.5\ k_B\log\ W$?

This question is probably wrong - however, I wish to understand even why it's wrong.. Let's take the monatomic gas situation. By the Equipartition theorem, we have that for every degree of freedom ...
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0answers
21 views

Non-state thermodynamics functions

I know that work and heat are non-state functions in thermodynamics because they depend on path between two states. Are there any others?
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1answer
67 views

Can an adiabatic, isentropic transformation be irreversible?

My question is very similar to this, but I decided to ask another question because I felt that the problem deserved to be addressed in a more specific and formal way and I also wanted to discuss a ...
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2answers
84 views

Why is water not considered a proper liquid in terms of thermometers?

We were just discussing about why liquids in general are used in glass thermometers. I was wondering why water isn't considered a proper liquid. Is it because of the way is expands differently to ...
1
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1answer
115 views

How are thermometers calibrated?

I know this is quite vague, but I was just thinking about it......like obviously now we mass produce things and we don't really think about them. But how was the first thermometer calibrated/how are ...
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3answers
72 views

Meaning of the phase space in statistical physics

I have a silly question about the phase space. I am confused with the meaning of points in phase space. Does the each point in phase space represent concrete particle of the system, or does it ...
2
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3answers
65 views

Does “IF isentropic THEN reversible” only holds for adiabatic processes?

I know that: IF adiabatic and reversible THEN isentropic First question: does the implication IF isentropic THEN reversible hold for adiabatic processes? Second Question: if yes to the above, are ...
11
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0answers
130 views

Why does temperature change the friction coefficient of my stovetop?

I have a Ceran cooking field at home, it's a glass-ceramic surface with heating coils embedded beneath. When I slide a pan around there's much more friction on a hot plate than on a cool one. Why? ...
0
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1answer
31 views

Calculate how much air will cool from an amount of ice? [closed]

So, there are $3kg$ of ice at $-18$ degrees Celsius and $50kg$ of air at $30$ degrees Celsius. I need to calculate how much the air will cool by the time the ice reaches its temperature. I thought I ...
4
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0answers
53 views

Question about Ginzburg-Landau Theory

I was reading CH3 of Reichl's "A Modern Course in Statistical Physics" on Ginzburg-Landau theory and don't really understand a couple of points he makes. He writes: I don't understand why the first ...
2
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1answer
86 views

What is the correlation between QFT and thermodynamics?

This may be a naive question. In physics many processes are symmetric, except a few involving entropy, or the arrow of time. Another one has to do with heat generation. We can generate heat, or energy ...
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0answers
89 views

Why does the method below work?

Please explain why this method works. I get this idea when try to solve adiabatic gas expansion by using numerical method. The analytic/exact solution for the expansion will be $PV^\gamma$=constant. ...
0
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2answers
73 views

How are laws proven in general?

This may be a bad question, but what are the ways that laws are proven? I would expect that some ways would include by proving them mathematically or through experimentation. My biggest question about ...
0
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1answer
32 views

What is the effect of volume on liquid temperature during evaporative cooling?

Imagine two evaporative cooling experiments: In the first, a beaker contains a known volume of liquid. The liquid starts at ambient temperature. The temperatue of the body of liquid remaining in the ...
0
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1answer
41 views

How does radiative cooling between the earth and space work?

On a chilly (but above freezing) temperatures on a clear night, you can freeze water outside because of radiative cooling. By what mechanism do warm bodies on earth actually lose heat to space? ...
0
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1answer
36 views

find the density of water only by its pressure?

Is it possible to find the density or specific volume of water, by only knowing its pressure? Or we need to know its temperature as well? I can't find any relevant table, so can you advise me please? ...
6
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1answer
54 views

How much of water's surface tension is entropic?

Water molecules on the surface of an air-water interface have preferred orientations that lower their energy. This implies that these molecules are not uniformly distributed in orientation space, ...
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0answers
37 views

When does $E=\frac{3}{2}pV$ hold?

I only know that it holds for classical (monatomic) ideal gas and quantum ideal gas. But does it hold for interacting classical gas (e.g. van der Waals gas)?
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0answers
47 views

Thermodynamics: Apartment Airflow: What Am I doing wrong air

Our apartment is a sauna. But sometimes it's much much hotter inside the apartment than it should be (night time it's 68 degrees outside but thermometer still says 90 inside!). I have 2 fans, one ...
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0answers
26 views

Book on thermodynamics for International Physics Olympiad? [duplicate]

I'm a junior in high school studying for the IPhO and I've started learning thermodynamics as part of my preparation. I have a guide to the exam that says things like this will be tested: Carnot ...
5
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1answer
66 views

Can the efficiency of a thermodynamic cycle be worked out from a pV diagram?

Is it true that a pV diagram of a thermodynamic cycle with a specified scale on both axes is enough to calculate its efficiency (such as the one below)? Is it the area within the shape divided by the ...
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0answers
40 views

Hot Water fountain experiment with mohr pipette

Why does water shoot out the tip of a Mohr pipette when half filled with hot water and turned upside down?
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2answers
28 views

Molar Specific Heat Definitions for Gases

In most textbooks, the molar specific heat of a gas is defined for gases at constant volume and constant pressure as follows : $C_v = \frac{Q}{n\Delta T} = \frac{\Delta U}{n \Delta T}$ $C_p = ...
0
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1answer
66 views

What are the problems in the idea that a person would freeze to death in outer space?

It is said that the body would freeze to death, if left in outer space, which is true, since the temperature is around $3$K. But what are the flaws in this theory, in terms of thermodynamics (if we ...
2
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2answers
75 views

Experimental confirmation of the textbook explanation for local entropy reductions

Clarification: In my original wording of this question, regrettably, I did not make it clear that I am interested in the the Boltzmann/Gibbs/statistical (BGS) interpretation of it, as opposed to the ...
6
votes
1answer
108 views

Adiabatic piston: why is Callen's argument flawed?

This question is related to this one. I would ask you to read that question and my answer to the question itself before answering this one. The problem is the following. In his book Thermodynamics, ...
1
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1answer
54 views

How do we measure the temperature of vacuum?

Afaik. temperature is in relation with the kinetic energy of the individual molecules. In vacuum there are only a few molecules so measuring their kinetic energy is very hard, because vacuum has a ...
0
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2answers
61 views

Is there a way to make atom move faster without heating them?

The more heat you add the faster the atom will move. This is something that is common knowledge. My question is it possible to make the atoms in let's say a gas move faster without adding heat of a ...
0
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1answer
49 views

Can/will a proton escape the nucleus when a force is applied? [closed]

Protons are contained within the nucleus of an atom. Protons carry a positive charge. With an electric field, we can exert a force on the proton. Is it possible for the proton to escape the nucleus? ...
4
votes
1answer
52 views

Which 'annihilation' processes dump energy to the cosmological plasma?

I have been considering a generalisation of the cosmological process involved in computing the temperature of the cosmic neutrino background. It is well-known that (simplistically) this temperature $...
0
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0answers
25 views

Fluctuation theorem - Tasaki Crooks

The Tasaki Crooks relation connects forward and backward evolution of a system which is initially in equlibrium: $$ \frac{P_F(W)}{P_B(-W)}=\mathrm{e}^{\beta(W-\Delta F)} $$ If the system would ...
0
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1answer
32 views

Do air particles always rush to fill a container? [closed]

I'm sitting here in the metro station, drinking a bottle of water, and watching how the flow of water out of my mouth changes as air rushes into the bottle. My questions is: in space, obviously the ...
0
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1answer
31 views

As hot air rises is the cold air that rushes in pushed in or sucked in?

I seem to remember from high school, the state of equilibrium. Volumes of more molecules wanting to get to a volume of less molecules and causing a state of equilibrium. From this I believe cold air ...