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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why the direction opposite to the heat energy of sound energy? [on hold]

The experimental studies of thermoacoustic cooler, shin-ichi sakamoto, the direction opposite to the heat energy of sound energy.
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37 views

Why temperature of liquid drops after spraying thru a nozzle?

We have tested in our lab as mentioned in the picture. We connected hot water at 130degree F at 40Psig to a nozzle(bottle sprayer).we measured the temperature differences inside tank and after ...
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25 views

Heat diffusion equation with time dependent specific heat capacity

What is the correct form of the heat diffusion equation in 1D if we take into account the temperature dependency of specific heat capacity? $$ \rho\frac{d(cT)}{dt} = ...
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10 views

Heat Engines and Thermal Pumps [on hold]

A steam engine is to have its thermal efficiency improved from 8.00% to 10.0% while continuing to produce 4500J of useful work each cycle. a) Does the ratio if the heat increase, remain the same, or ...
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8 views

Model for temperature and pressure inside a heated vessel with liquid being pumped into it

I am working on a problem where a pressure vessel is pressurized by heating the vessel to a high temperature and then injecting a liquid into the vessel that boils and hence increases the pressure in ...
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18 views

Timescales for isothermal processes

My understanding is that processes in ideal gases need to take place over relatively long timescales to be idealised as "isothermal" such that the gas temperature can be assumed not to change. For ...
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26 views

Landau theory of phase transation

In his article http://www.ujp.bitp.kiev.ua/files/journals/53/si/53SI08p.pdf, Landau defines probability distribution $\rho$ which is related to symmetry of crystal. If crystal has certain symmetry ...
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25 views

How to calculate liquid pressure regardless of the gravity?

Assume we have a balloon in a tank filled with a liquid , without any gravitational forces: We just know the Temperature, V0 and V1 I want to calculate the pressure exerted from the liquid on the ...
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1answer
22 views

Turning ice into water in a calorimeter with steam? [on hold]

So there's this question I've been having trouble with here it is: A 0.050-kg copper calorimeter contains 0.050-kg of ice at -10°C. What mass of steam at 100.0°C is required to convert the ice to ...
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What would it be like “inside” a star?

This question was triggered by a discussion regarding the computer game Elite: Dangerous, where spaceships routinely operate in close proximity to stars (two or three light seconds away), at which ...
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22 views

Pressure change with adiabatic compression problem [on hold]

So, I have to solve this problem: 2 moles of a perfect gas are compressed from $p_1=10$kPa to an unknown pressure, $p_2$. Throughout the process the temperature changes from $T_1=273.15K$ to ...
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21 views

How does antarctica stay frozen? [migrated]

Antarctica is receiving heat from the Sun everyday, so how does it stay frozen? I have made some thoughts about the answer but unsure of whether it is correct I hope people here can clarify. The ...
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1answer
38 views

Why is the Specific Heat of Helium 36 times greater than Xenon?

Given that these are single atoms, why should the specific heat difference be so great? And more specifically, why does it take 36 times as much energy to raise the temperature of a given mass of ...
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9 views

first law of thermodynamics ATMOSPHERIC HEAT' [on hold]

my system directly draws heat from the atmosphere and produces energy. my system according to the theory would provide energy continuosly. can anyone give me assisstance in solving my problem
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32 views

Which one will come to the room temp. faster? [on hold]

Suppose there is a bottle of water at 10 degrees C and ice at -10 degrees C both in a room, where temperature is 0 degrees C. Which one will come faster near the room temperature?
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2answers
31 views

Which is a more effective cooling method?

Assume I have a refrigerator at 0C and I put a can of soda at the center of the refrigerator. The temperature inside the refrigerator will be increased to 5C after I put the soda in, but will go back ...
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1answer
35 views

When to use h = Cp∆T or u = Cv∆T

I'm getting myself confused on when to use h = cp∆T or u = cv∆T where cp is the specific ...
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8 views

Comparing work required at compressing gas & pumping liquid

In one of online lectures comparing Vapour compression cycles (conventional refrigerators) with Thermal compression cycles (absorption chillers) it was said that former required more 'high quality' ...
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32 views

Maxwell Relations in Thermodynamics - Specific Heat [on hold]

I am not able to solve that question: Using Maxwell relations and the fact that $C_p = T \dfrac{\partial S}{\partial T}\Big|_p$ $C_V = T \dfrac{\partial S}{\partial T}\Big|_V$ Show that I can ...
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How do I calculate temperature diffusion in a gas contained in a heatsink?

To simplify the problem, consider a sphere with a diameter of $25\mathrm{mm}$ inside an infinite heatsink at $300\mathrm{K}$. At $t=0$ I instantaneously raise the temperature of the gas in the ...
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23 views

Is the diffusion coefficient time-dependent?

It is known that in the partial differential equation: $$u_t=au_{xx} $$ within the limits $0<x<1$ and $a>0$, the diffusion coefficient, arises in the mathematical modelling of a process of ...
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36 views

Is it possible to efficiently extract phonons from a lattice?

The population inversion generated in lasers occurs in multi-level atomic systems. As an example, the Nd:YAG energy diagram is shown below. The pump pushes the Nd ions up to the upper levels, and ...
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28 views

Convection and radiation heat transfer

It's been some years since my last physics exam and I really need a refreshment in this. I'm stuck in getting a rough estimation of heat exchange between 2 objects separeted by air: let's say object 1 ...
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2answers
33 views

Entropy change in an irreversible process between 2 equilibrium state

Calculating entropy change in an irreversible process between 2 states requires computing the change in entropy for any reversible process between the 2 same states, but why? If someone could provide ...
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1answer
149 views

Do some of the laws of Thermodynamics break down in Quantum Mechanics?

I do not know if this is a stupid question as i am not an expert in thermodynamics and certainly no expert in QM. So,we know that the laws of thermodynamics are laws based on statistics.thus require ...
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2answers
24 views

Can inefficitiencies of electrolysis be overcome using batteries charged by alternators? [on hold]

We know that you cannot create a perpetual motion motor. But, what if you could produce a two stage motor. A battery that begin the electrolysis of water providing a combustion engine with burnable ...
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1answer
27 views

Spin correlation function identity

The correlation function G between two spins is usually defined as $$ G=\langle \sigma_a \sigma_b\rangle - \langle \sigma_a\rangle \langle\sigma_b\rangle $$ The $\sigma$ are the value of the spins ...
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43 views

How fast do I have to dry myself for a hot shower to heat my body?

I am not a physicist. I would like to know how fast do I have to dry myself after taking a hot shower to get more heat from the shower, than lost because the water on my skin increasing heat exchange ...
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16 views

Does the heat flow vector depend on the proximity of isotherms?

Suppose, there be two isotherms at varying temperatures. Heat energy will flow from higher temperature isotherm to the lower; thus we can assign vector to each point & it will tell about the rate ...
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32 views

Are there laws/equations regarding how a specific material heats up above ambient?

I'll preface this question by saying that I have limited knowledge of physics, especially in thermodynamics, so please bear with me. The goal I have an electrical resistor, like the one below (nice ...
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22 views

How is the Joule normalised?

Apologies if this question is a duplicate, I tried searching for this question both on Google and here, but was unable to find an answer. A Joule is defined in various ways, some of them being: ...
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20 views

Fuel Saved through different routes

Can you save fuel and if so how much in a diesel engine traveling from point A to point B? Mountaineous Terrain. Shorter dist. or longer one? please answer.
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1answer
23 views

Rough/ballpark thermodynamics and black body temperature question

This is probobly pretty basic but I got into a debate with someone and the temperature of Titan came up, and I did some quick and dirty calculations - as follows. Titan is about 9.5 times as far from ...
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1answer
36 views

Can bulk modulus ever be negative? Can somebody illustrate with an example!

I was particularly confused when my teacher proved that $C_p > C_v$ for substances other than ideal gas for which the difference between the two is R . However the proof involved assuming that the ...
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20 views

What does these $\Delta \Delta G$ numbers signify? [migrated]

I was reading a paper and came across this table showing $ \Delta \Delta G$ numbers of different nucleotide sequences in DNA/RNA. I know that $\Delta G$ is free energy and $ \Delta \Delta G$ is ...
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38 views

Are reversible and irreversible processes frame dependent?

since it is all about time. If I have a look at an irreversible process from a frame where time runs really slow. is there a possibility of considering that process reversible from that frame?
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3answers
218 views

Why does the system move until equal temperatures are obtained?

In my college level thermodynamics class, the teacher gave us the example of a closed system which consisted of a box thermally insulated. A piston fully divides the box in two parts, and each is ...
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1answer
39 views

Temperature in a vacuum made in the lab

Is the thermal energy of a vacuum 0? And, how close to a perfect vacuum can we make in the lab?
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1answer
39 views

Kinetic energy of different phases of water [closed]

In a closed flask at zero degrees Celsius, all three forms of water exist. Which form of water will have the maximum average kinetic energy? The answer is that all forms of water will have same ...
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2answers
40 views

What is the best thermal heatsink compound?

Re-worded This is about the Experimental Physics not PC building or how to grease a car's radiator. I have to insert a stainless steel enclosed PT100 into a block of metal to monitor its temperature ...
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How much temperature reduction can we expect when pouring water into the cup from an elevated kettle?

Turns out some people who are into green tea use the following technique to cool the water from the kettle down. They lift the kettle and pour a rather thin stream of water in the cup. Because of high ...
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0answers
26 views

Gibbs free energy of a biological redox reaction [closed]

I am having some trouble understand the right way to go about this problem. I need to calculate the free-energy change of the reduction of a molecule of pyruvate by NADH. I am given the following: ...
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0answers
8 views

Internal energy given surface tension

Could anyone offer some insight for the following problem: The internal energy and the entropy are proportional to the area. Show that the internal energy per area is given by $$u(T) = \frac{U}{A} = ...
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1answer
35 views

Work needed to pump the balloons

Let's suppose that we want to pump the balloons underwater from the initial volume $V_0$ to the volume $V_1$. The pressure there equals $p_1$ and the atmospheric pressure is $p_0$. It is claimed ...
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38 views

getting frm micro to macro entropy problem

For an ideal gas entropy forvolume change from micro to macro can be rewritten as: $S=k\ln W$ $\Delta S= S_2-S_1=k\ln W_2-k\ln W_1=k \ln\frac{W_2}{W_1} $ since we are constrained from derivation ...
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1answer
50 views

Limitations of Redlich-Kwong equation of state

I have been using the Redlich-Kwong EOS to calculate the compressibility factor for nitrogen. I am currently running an Excel VBA that performs the calculation. I have noticed that the process of ...
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1answer
22 views

Pressure calculations of 2 volumes separated by a membrane [closed]

I am working out the formulas for a system described as follows: 2 volumes ($V_1$ and $V_2$), both of size $V_0$ Volumes are both separated by a membrane The 2 volumes are subjected to mass flows ...
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9 views

Does a sonic pulse in a gas enhance thermal mixing?

I have a sonic pulse consisting of around 10 cycles that is propagated longitudinally through a gas in a tube. If there are thermal differentials in the gas (say between case and central portion of ...
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Thermal de Broglie wave length

If we refer to this wiki page thermal de Broglie wave length, we can see there are two expressions. One is derived using equipartition theorem, which makes perfect sense. The other one used $\pi kT$ ...
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1answer
210 views

Heat Transfer through a wall

If a volume of air enclosed by a physical box is kept at a constant temperature that's different from the temperature outside, will the temperature of the inner wall of the box be the same as the ...