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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A gas close to zero Kelvin

Consider an adiabatic expansion of an ideal gas that work is done against friction or a piston. Since no heat exchange can occur the gas keep on losing energy and its temperature decreases and the gas ...
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48 views

How much electricity could be generated by cloths made of thermocouples?

Lets say that we made a glove, shirt, pants and a hat out of the most effective thermocouple material available today. How much electricity would be generated by each, by a healthy person, on a cool ...
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426 views

How much energy in form of heat does a human body emit?

How much energy in form of heat does a human body emit at rest level?
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147 views

role of entropy in gibbs free energy intuition

I have looked at various derivations of the Gibbs free energy equation and the underlying definition of the gibbs free energy. However I have been unable to attain direct insight/intuition over the ...
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76 views

Can 'Backradiation' warm its own source? [duplicate]

Ok, although this question arises out of the global warming debate, this is a question purely for physicists and not intended to branch into that particular debate. We are told that LWIR from the ...
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100 views

Container divided in two parts with ideal gas

I wanted to ask your help with the following problem: Consider a closed container, that is, with insulated walls impervious, and rigid. The container is divided into two parts by a wall having the ...
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77 views

Details in the derivation of the second law starting from the phase space volume

I had a question on one of the details of the derivation of the second law of thermodynamics starting from the phase space volume. I'll type out what I understand so far: Letting the Hamiltonian ...
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290 views

Would sea water moderate a nuclear submarine meltdown?

My son asked me: If nuclear submarines get sunk or blown up, what is to stop them going into nuclear meltdown? I thought about it and came to the conclusion that because they're in the sea the ...
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245 views

Work done by isothermal expansion from two different viewpoints

Consider an adiabatic system as follows. It consists of a gas in a container and a piston. Initially, the system is at equilibrium and the gas inside it occupies a volume $V_i$ at a pressure $p_i$ ...
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234 views

How do I calculate the curve of a parabolic mirror to melt the ice from my street gutter?

I want to make a concave parabolic mirror that will have a focal point six inches below where I place it (on the edge of the sidewalk) so that it will melt the ice collecting in the gutter below and ...
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122 views

What happens when a black hole dies?

It just vanishes into space leaving nothing behind or does it expel some material? Also, talking more about black holes, as far as i understand the term "temperature", it is defined by the amount of ...
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79 views

Change of heat capacity fluid when you add solvent

I am considering a liquid for which I know $C_p$ or $C_v$. I am wondering how this changes when you add a (minor) amount of solvent to the liquid. Is there a general theory around describing how a ...
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429 views

Probability of Different States - Canonical Ensemble - Partition Function

Consider a canonical ensemble of $N$ ideal gas atoms, which could have spin up or spin down. Why is it that the probability of finding the particle in a spin up state generally only involves the ...
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258 views

How does that Boltzmann distribution interact with entropy?

In an ideal gas, the Boltzmann distribution predicts a distribution of particle energies $E_i$ proportional to $ge^{-E_i/k_bT}$. But, doesn't entropy dictate that the system will always progress ...
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234 views

Volume quotient in Carnot-cycle

Problem: One kilomole of an ideal, monatomic gas undergoes a reversible Carnot-processes between temperatures 300 °C and 20 °C. The work done during one cycle is 1500 kJ. a) Find the ...
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156 views

Why is $0 \,\mathrm{K}$ so special?

I know that $0 \,\mathrm{K}$ cannot be reached, this is discussed here and here. But, why is it such an important statement? I mean, there are many properties which will never be zero, like: ...
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2k views

Would a Cup of Tea Be Hotter If you Add the Milk Before or After Boiling Water?

This is a bit of dispute between work colleagues. An answer would be greatly appreciated. My argument is as follows: If you add X amount of milk at a temperature of M to a mug at room temperature R ...
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332 views

Understanding heat pump efficiency

I have read that heat pumps are more efficient than generating heat directly for heating homes, until the temperature gets down to a critical value. I just asked how to calculate temperature of ...
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135 views

Deriving the condtion for spontaneity using gibbs free energy

While deriving the condition for spontaneity, $\Delta$G$\leqslant$0, we start by saying that $\Delta S_{tot}$ $\ge$0 $\Rightarrow$ $\Delta S_{sys}$ + $\Delta S_{surr}$ $\ge0$ If $Q$ is the heat ...
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639 views

Pressure derivatives of the bulk modulus of materials? (Solved) [closed]

Isotherm bulk modulus is defined by $$K=\rho\left(\frac{\partial p}{\partial\rho}\right)_T=-v\left(\frac{\partial p}{\partial v}\right)_T$$ wherein $v=\tfrac{1}{\rho}$ is the specific volume. Studying ...
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130 views

Clarification on the Seebeck Effect

Alright, I've been interested in the Seebeck effect lately, so I've been trying to learn it. From what I understand, this is measured with the Seebeck Coefficient, which gives you the $\mu\textrm{V}$ ...
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1k views

Thermodynamic cycles, when is the work negative/positive?

ever since I begun calculating thermodynamical cycles, I've had problems with determining the sign of the work along a particular bit of the cycle. Of course, I guess that an arbitrary cycle is ...
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94 views

How to homegrow large, momocrystalline water ice crystals

This is a follow up to this question:Can one get clear ice crystals from a dirty suspension?. How could one grow a large - meaning visible with the naked eye - water ice crstal with common household ...
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223 views

Why increase pressure to go from liquid to steam?

Assume the following phase diagram $T-H$ of water At a nuclear engineering course, I was told that in order to increase the performance of a pressurized water reactor, one has to increase the ...
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324 views

Does increasing the pressure of the gas in a container by pumping gas into it increase temperature?

Basis is the ideal gas law: http://en.wikipedia.org/wiki/Ideal_gas_law This law only states a mathematical relationship between many variables. It does not state what happens if one of the variables ...
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52 views

Gas Circulation Using Pressure Difference

Dear all, see attached picture Please, is it possible to have the gas recirculated from the gas phase to the liquid as described in the diagram assuming the gas is not soluble in the water. These ...
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117 views

Is the crystallization of a heat pack the same as the crystallization of freezing water?

Is the crystallization of a heat pack the same as the crystallization of freezing water? If so, why does one generate heat where the other does not?
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160 views

How can dQ/T be interpreted as a system's level of disorder?

Long before statistical mechanics, entropy was introduced as: $dS = \frac{dQ}{T}$ At the time when entropy was introduced in this manner, was it known that entropy represents how "disordered" a ...
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253 views

Phase volume contraction in dissipative systems

I am confused about phase-volume contraction in dissipative systems. Please help me catch the flaw in my understanding. From a macroscopic point of view I understand that a dynamic system tends to go ...
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160 views

fitting van der waals law on real data

For an examples class on thermodynamics, I would like to fit Van der Waals law on data of real gasses, say $CO_2, H_2O_2, CH_4$. I want to set out measurements of pressure and volume at constant ...
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791 views

Thermal expansion of Sphere

How would one go about writing an expression of the expansion of the volume of a sphere of a given material? I noticed a few sources give it as $\Delta V= 3\gamma V\Delta T $ where V is the initial ...
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4k views

Work Done in an Isobaric Process

I am given the information that an air parcel undergoes isobaric heating from 0° C to 20° C, and that's all I'm given. I have to determine the work done by the parcel on its surroundings. I know that ...
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305 views

Problems in the modern semiconductor/electronics technology?

From what I have read, the problem with modern semiconductors/electronics seems to be quantum tunnelling and heat. The root of these problems is the size of the devices. The electrons are leaking out, ...
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Constant Volume vs. Constant Pressure?

Approaching the following question: Consider two experiments in which 2 moles of a monatomic ideal gas are heated from temperature $T$ to temperature $T + \Delta T$: in the first experiment ...
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Heat of vaporization of water - dependence on relative humidity?

Does the heat of vaporization of water depend strongly on the relative humidity of the gas into which it evaporates? Some context: If we want to calculate the dew point of water, we find the ...
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627 views

Ideal gas in a vessel: kinetic energy of particles hitting the vessel's wall

Reading Landau's Statistical Physics Part (3rd Edition), I am trying to calculate the answer to Chapter 39, Problem 3. You are supposed to calculate the total kinetic energy of the particles in an ...
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123 views

Kerr-Newman black holes and infinite charge

Recall the first law of BH thermodynamics $ dM=\frac{\kappa}{8\pi} dA + \Omega dJ + \Phi dQ $ Now, let's consider the Reissner-Nordstrom solution $J=0$ such that $m>Q$ but only slightly greater. ...
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1k views

Equations instead of psychrometric charts

I want to create a program that will accurately simulate a condensor. I want to use the data in psychrometric charts. But I cannot and hence want to use equations that show similar data. Any idea ...
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232 views

How to express the heat capacity in terms of heat?

The first law of thermodynamics divides the internal energy change into contributions of heat and work. $$\text dU=\omega_Q-\omega_W,$$ Here I chose the notation to emphasise that the two parts are ...
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3k views

Which is more efficient, heating water in microwave or electric stove?

So our propane tank in the kitchen ran out again today. Which is more energy efficient, boiling water in a microwave on an electric stove? All things being equal i.e. starting temperature and mass ...
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457 views

Steady State Temperature of an Object Orbiting the Earth

This may be irrelevant or stupid to ask but I couldn't come up with a good answer. At least, we could not agree on with my friend the other day. I would like an estimate of the temperature of a human ...
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6k views

Best way to solve P-V-T Question

Typically in an exam or problem set we have a problem that's like this: Determine the specified property at the indicated state of water. Locate the state on a sketch of the T-v and P-v diagram. p= 3 ...
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232 views

Is rocket propellant meaningfully a form of “space junk”

I imagine that most people are familiar with the concept of space junk (or space debris), which is a hazard to space exploration that grows with every item that humans leave in space. Wikipedia lists ...
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2k views

Simple formula for liquid heat transfer

I'm trying to do a simple simulation of a solar panel coupled through some piping to a boiler, with the aid of a pump. My input constants could be something like: volume of liquid inside the panel, ...
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896 views

Evaporation from a capillary tube

Consider a capillary tube (say from a liquid / capillary thermometer), that means a tube of small internal diameter which holds liquid by capillary action . The tube is fulfilled with water and closed ...
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380 views

Violations of Dulong-Petit rule as an upper limit to heat capacity

Does any known substance have a heat capacity at constant volume ($C_V$) per mole of atoms greater than $3k_B$ ~ 24.94 J/(mol K)? In order to count, the substance must actually be made of atoms, that ...
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278 views

Heat reflection on distant planets

I was watching a documentary last night on the first planet discovered outside our solar system. The first one apparently is a giant gas planet that orbits very close to its sun over a very fast ...
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28 views

Thermodynamics - ideal gas [closed]

Question: 1 mol of a monoatomic gas at 298 Kelvin acquires a volume of 3 litres. It is expanded adiabatically and reversibly to a pressure of of 1 atm. It is then compressed isothermally and ...
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How can we tell if a molecule is in thermodynamic equilibrium from scattering data?

We have a molecule that is emitting/absorbing photons. We know the Hamiltonian and that there are several levels. We count the emitted photons at different angles and frequencies. We can also do ...
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74 views

Calculating Boltzmann constant using semiconductor

My task from the latest laboratory exercise in physics is to calculate Boltzmann constant from known temperature, current and voltage. We were given this circuit: By changing the resistor value, I ...