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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9 views

Which materials absorb heat?

Which are the materials that absorb heat? and can i somehow convert that absorbed heat into a different form of energy? I am looking into trying to absorb the wasted heat dissipated by laptops,severs ...
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1answer
10 views

does the internal energy and enthalpy of the GAS changes in a free expansion process?

when a balloon kept in an evacuated room is punctured and the ideal gas in the balloon goes on to fill the entire room,does the gas perform any work in this expansion, and is there in any change in ...
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1answer
21 views

Seeking Reference on Transport of Momentum by Diffusion of Mass

I'm looking at continuum mechanics from the perspective of De Groot and Mazur's "Non-Equilibrium Thermodynamics" - the first reference that I've come across that seems to do a good job of bringing ...
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1answer
33 views

Can gas return back into a sparkling beverage on cooldown?

We all know that if a sparkling beverage (let's say, CocaCola) spends some time outside of the fridge and gets warm, the gas comes out of the liquid, rises the inner pressure and makes the bottle ...
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7 views

Increased pressure of Liquid Pitch and Limestone (Bitumen/Asphalt) @ approximately 300 degrees Fahrenheit

If liquid pitch and limestone (20/80 mostly limestone) is pumped (appx. 5 gpm) out of a nozzle that restricts the flow compared to the flow that would be achieved straight out of the pump ( no ...
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1answer
46 views

Electromagnetic cooling

Heat means stored kinetic energy in matter. Microwave owens and induction heaters works on increasing kinetic energy on matter. Is it possible to make inverse of this heaters like cooler. Can we ...
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26 views

What do physicists mean with “classical critical behaviour”?

What do physicists mean with "classical critical behaviour"? As far as I am concerned it should be "power law behaviour" of some quantity close to the critical point but I ask here to be sure.
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12 views

Specific heat capacity for constant volume and constant pressure

I have seen in some exercises that the specific heat capacity for constant volume, $c_{vo}$ and the specific heat capacity for constant pressure, $c_{po}$ , where the $o$ indicates that we are ...
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2answers
44 views

Different materials have different temperatures?

Why do two materials, under the same weather, have different temperatures? I have a small clue about it. For example, iron and wood supposed under the sun's radiation, and if we touch both of them, ...
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25 views

Work done by a gas in an expansion [duplicate]

1) Consider a gas expanding quasistatically and reversibly from $V_1$ to $V_2$ at constant temperature. I want to calculate the work done. So by convention work done by a system is a negative quantity ...
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8 views

What is the heated added and changes in internal energy? thermodynamics

A piston + cylinder initially contains 2 x 10-3 m3 of helium gas at the pressure of 1.01 x 105 Pa and with a temperature of 60'C. The gas is heated allowed to expand at a constant pressure until its ...
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14 views

Heat energy question [on hold]

An aluminium block of mass 1 kg is heated by an electric heater for 3 minutes and a temperature rise of 15 °C is recorded. If the electric heater is connected to a voltmeter which gives a reading of ...
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21 views

Classifying solutions of equation of state as functions of temperature [on hold]

I've got an exam in 2 days and the past papers don't have solutions. I'm given this equation of state: $$ p + a\frac{N}{V} = \frac{Nk_BT}{V-bN}$$ and asked to classify the solutions as functions of ...
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2answers
47 views

what is the temperature (and pressure) of the oxygen inside an oxygen bottle?

In the hospital or in a lab, one can see the huge oxygen bottles. A question is, what is the temperature of the oxygen inside the bottle? And what is the pressure inside? We know the critical ...
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0answers
24 views

Find the time needed to warm the water to a temperature [on hold]

An electrical resistence has a power of 1 kW. It is put inside a container that has 10 liters water. The water is in temperature 20C with pressure 1 atm. Find the time to warm the water to the ...
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17 views

Find the molar specific heat for each gas [on hold]

A mixture of two ideal gases, the first one atomic and the second two atomic are put in normal conditions in a calorimeter with volume 1 liter hermetically closed. After it is given 10J thermal energy ...
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1answer
35 views

Find the velocity of the escape of the bullet

A gun has a muzzle 0.8 meters long and with a diameter of 0.006 m. A bullet with mass 0.002 kg is initially 0.01 m away from the end of the muzzle. As a result of a gunshot, the pressure of the gas ...
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0answers
32 views

Specific heat at constant volume

Me and my friend came across this derivation is some lecture notes of our thermal physics module. We have been trying to calculate the partial differential of the internal energy but cannot get the ...
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2answers
47 views

derivation qm canonical ensemble

In classical mechanics the canonical ensemble can be derived from the microcanonical ensemble of two systems in weak interaction. Is a similar thing possible in quantum mechanics? Is there any good ...
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1answer
41 views

Struggling with whether its $\pm p dV $

I am struggling to understand when calculating the work done by a gas whether it is postive or negative p. It my notes and in many other notes sometimes it is $-pdV$ and sometimes it is $pdV$. I ...
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13 views

Chemical potentials of SM particles at high temperatures

Recently I've heard the statement that chemical potentials of SM particles on $T > 1 \text{ GeV}$ are very small, so that Gibbs potential reduces to free energy. How to prove this statement? Does ...
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0answers
17 views

Superficial velocity as a function of position along flow path

I am wanting to estimate the superficial velocity of a fluid as a function of position. The system I'm trying to evaluate is as shown below: A cylinder of porous media with the source acting on ...
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1answer
24 views

entropy change during irreversible heat loss [duplicate]

When a thermodynamic system gains heat if the heat gain is irreversible then there is a entropy generation along with the entropy transfer..so is there a similar entropy generation associated with ...
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2answers
52 views

clausious inquality

Take a reservoir which gains a heat Q irreversibly at temp T from a surrounding at temp T0 then the entropy change of reservoir is given by Q/t and that of the surrounding is -Q/T0...How is this ...
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27 views

Why the heat capacity doesn't diverge in the Kosterlitz-Thouless (KT) phase transition?

The KT transition has a special properties that, during the phase transition the heat capacity stay finite (so the behaviour of the heat capacity cannot reflect any critical behaviours). However, the ...
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1answer
28 views

Show that change in internal energy equals zero for an adiabatic process with incompressible fluid

I have a problem when solving an exercise in thermodynamics. I am supposed to show that when we have an open system, where the process is adiabatic with an incompressible fluid, it follows that the ...
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1answer
31 views

Helmholtz Free Energy vs Gibbs Free Energy in Landau Theory

When I was studying thermodynamics potentials for the first time, I learned that keeping the pressure and the temperature constant, the Gibbs Free Energy is a minimum, also, if we maintain the ...
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1answer
48 views

Changing the melting point of ice

Myself and a friend have been stuck on this problem for a while now. We know that we should end up with an answer of $-0.007K$ however, cannot get to this solution. Help with the method we should use ...
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0answers
20 views

Internal energy of a molecule and bonding strength

I had a lecture on thermodynamics. I was told that the bond strength, $\epsilon$, is related to the latent heat of sublimation, $L_s$. $L_s\approx L_f+L_v$ if the melting and boiling points are close, ...
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52 views

What liquid would wick away heat most quickly?

I've read and seen on various "life hack" websites that if you've forgotten to chill drinks, wrapping them in a wet paper towel and sticking them in the freezer for a few minutes rapidly cools them ...
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1answer
57 views

Why bodies lose heat faster in water than in air?

A simple question. In several places, including this very recent and already famous paper http://www.sciencemag.org/content/348/6236/786.short it is stated that bodies lose heat in water very fast ...
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0answers
23 views

Magnetic moment of a paramagnetic crystal

I've been having some trouble with a paramagnetism problem from my Statistical Mechanics class textbook (F. Mandl, Statistical Physics, 2nd edition, p. 25). The problem is as follows Since the ...
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2answers
52 views

Fan Speed Formula

Is there any formula for computing fan speed by using air mass,air flux, air density or specific heat? I have computed air mass and air flux, and found the values for air density and specific heat, ...
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37 views

Entropy of a system of gravitationally interacting particles

Lets suppose there is a container in space where there are some particles moving very fast. But due to gravitational attractions between the particles they would just come to a corner of the box. ...
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28 views

Thermal Equilibrium of two thin sheets

While reading Gibbs' Elementary Principles in Statistical Mechanics I came across this footnote: The most simple test of the equality of temperature of two bodies is that they remain in ...
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1answer
42 views

Pressure, density, volume and mass in a room

Here's the question. A window in the room is open. The next day, the temperature of the room has increased, but the pressure of the air stayed the same. State and explain what has happened to ...
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1answer
270 views

How hot would tritium water be?

I realize this is kind of a silly question, but if you have tritium water, with the tritium half life of 12.5 years, I expect it would be quite hot. (note, this is not a homework question, I'm just ...
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1answer
25 views

Triangular Cyclic Process

i am currently studying for my physics exam and i am trying to wrap my head around cyclic processes. There is the cyclic process - ![1]: (http://imgur.com/7i0JF1S) "cyclic process" We know its an ...
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1answer
65 views

Highest temperature possible to achieve using magnifying glass and sunlight [duplicate]

Temperature of the surface of the sun is about 5750K. Can you heat an object to more than 6000K using magnifying glass and sunlight? According to second law heat cannot be transferred from colder to ...
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1answer
42 views

Why should slope of pressure versus volume always be negative?

I read that the slope of the pressure, ($P$), versus volume ($V$) graph should always be negative for thermodynamic stability, but there was no further explanation in the text. Could someone give an ...
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1answer
48 views

Transfer of heat through a finite temprature difference

Consider the following derivation There are two reservoirs at temp A & B at temp T1 & T2 .They are connected by a metal rod such that T1 > T2. Q amonut of heat is transfered ...
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3answers
58 views

Feasible way to cool water (ice) to temperatures around -20 degree celsius

Is there an easy way to cool water to temperatures around -20 or -30 degree celsius that is economically and technologically feasible for a high school student. Can it be done using typical household ...
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0answers
14 views

Why is the boundary layer thinner on the outside of an outer wall versus the wall inside the house

The convection on the outer suface of the outer wall of a house is larger, because outside a house it's more windy compared to inside. More wind means more turbulence which leads to more transfer of ...
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1answer
30 views

entropy change during heat loss

When a thermodynamic system gains heat if the heat gain is irreversible then there is a entropy generation along with the entropy transfer..so is there a similar entropy generation associated with ...
4
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2answers
255 views

Is it possible to build an air compressor with no moving parts? [closed]

Is it physically possible to build an air compressor with no moving parts? A thermodynamic cycle capable of compressing air with no moving parts and operate it in stationary way. EDIT I will add a ...
2
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1answer
29 views

Entropy Change for a Thermally Isolated System

Clausius' Theorem states that $\int\frac{dQ}{T}\leq0$ for a closed cycle, with equality for a reversible cycle. Suppose we wish to take our system around a closed cycle such that the path from A to B ...
2
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1answer
23 views

Is it safe and theorotically correct to heat a bar magnet using an open fire/furnace, provided conditions given below?

For a project, I will have to heat a bar magnet to any temperature above 40 degree celsius. For this, can I place the magnet over an open fire --like one in a furnace-- for 20 minutes or so to achieve ...
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1answer
38 views

Calculations on heat transfers [closed]

An unclothed person whose body has a surface area of 1.4m^2 with emissivity of 0.85 has a skin temperature of 37 °C standing in a 20 °C room. How much heat does the person lose per minute?
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1answer
77 views

Does time freeze at Absolute Zero? [closed]

Time has many definitions per se, but the basic idea being it's "the measurement of change" so as we know, all matter looses it's ability of changing with the loss of kinetic energy. and the where it ...
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1answer
55 views

Entropy change in mixing two gases

The entropy change of an ideal gas is calculated as \begin{equation} \Delta S = C_V n\ln(\frac{T}{T_0}) + nR\ln{\frac{V}{V_0}} \end{equation} derived by integrating $dU = TdS - pdV$. It is only true ...