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Stretching vs bending of thin membrane

Not sure exactly what you are asking, but maybe this helps. You defined stretching as being associated with tension. But there is also the opposite "compression" situation where you shorten ...
Mariano G's user avatar
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Penning trap laser cooling

Great question! The electrostatic potential that helps to trap the particles is of the form $$ \Phi_\text{trap} \propto x^2 + y^2 - 2z^2 \quad .$$ The potential that helps to couple axial and radial ...
Martin J.H.'s user avatar
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1 vote
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Reference frame of equipartition theorem kinetic energy

If $E$ is the internal kinetic energy of the molecules of the system, then the reference frame is the center of mass (COM) of the system. This distinguishes the internal kinetic energy of the system ...
Bob D's user avatar
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Does doing work on system increase or decrease its internal energy?

Does doing work on system increase or decrease its internal energy? Doing work on the system always transfers energy to the system, thus adding to the internal energy of the system. But whether or ...
Bob D's user avatar
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4 votes

Why doesn't capture of infinitely rare ions by microbes in an infinitely large ocean cost infinite free energy?

If a K+ ion has a (near-)100% chance of being captured, then the resulting bond is quite strong, and the corresponding energy release from forming that bond is notable. This energy heats the cell and ...
Chemomechanics's user avatar
2 votes

Why doesn't capture of infinitely rare ions by microbes in an infinitely large ocean cost infinite free energy?

If a K+ ion has a $100$% chance of passing through a receptor when it gets near enough to the outside, it would also have a $100$% chance of passing through when it got near enough the inside. If the ...
mmesser314's user avatar
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5 votes
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Does doing work on system increase or decrease its internal energy?

If $\Delta V$ is negative due to compression of the gas, then the sign of the work is positive and the internal energy will increase. The convention used here is that the sign of the work done on a ...
Matt Hanson's user avatar
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-1 votes

Is there any difference between relative motion and motion itself

Actually motion is a relative term, there is nothing like absolute motion but the motion with respect to ground is generally considered as absolute motion. Motion is always defined with respect to a ...
Het Patel's user avatar
0 votes

Why is Sun's energy entropy low on Earth?

Near the sun the temperature of the thermal energy of the photon gas is quite high, and the amount of thermal energy of the photon gas is quite high, that is why the entropy of the photon gas is quite ...
stuffu's user avatar
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0 votes

What regulates the size of our atmosphere?

The Karman line of 100 km, as you might guess, is a fairly arbitrary legal definition rather than one based in physics or meteorology. But it is roughly the altitude where a plane would have to ...
RC_23's user avatar
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0 votes

What regulates the size of our atmosphere?

Yes, we are just lucky! And not just about the amount of air, but about nearly everything that has made this little blue planet able to sustain life.
BlastWave's user avatar
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Is this interpretation of Enthalpy and Internal Energy correct?

This question is not a physics question. Enthalpy is an engineering concept that was introduced in the 19th century to assist in calculations about steam engines where there is state change between ...
BlastWave's user avatar
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Is the second law of thermodynamics a fundamental law, or does it emerge from other laws?

My one cent. According to some physicists, the second law of thermodynamics is simply a statistical and emergent law (eg as in the form derived from fluctuation theorem) that can be violated, although ...
Nikos M.'s user avatar
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Does Fluctuation Theorem prove the 2nd Law of Thermodynamics?

My couple of cents. Fluctuation theorem leads to a specific formulation of the Second Law of Thermodynamics as manifested in the statistical effects over large number of particles and/or over long ...
Nikos M.'s user avatar
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1 vote
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Contradiction in the Carnot Cycle?

You are talking about two different temperature differences. The first is the temperature difference between the heat engine and the thermal reservoirs during the isothermal expansion and compression ...
Bob D's user avatar
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1 vote

Contradiction in the Carnot Cycle?

There is no contradiction. The Carnot cycle has 4 stages consisting of two isothermal stages, one at a temperature $T_1$ and the other at a temperature $T_0 < T_1$, say, and two adiabatic stages. ...
hyportnex's user avatar
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3 votes
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Enthalpy at constant pressure/volume

Enthalpy is defined as $H=U+pV$ irrespective of what process the system is subjected to. It, enthalpy $H$, is a state function and in equilibrium thermostatics its definition has nothing to do with ...
hyportnex's user avatar
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0 votes

Does Kirchhoff's law of thermal radiation fail for optically thin sources?

For an optically thin material in thermodynamic equilibrium, $S_\nu = B_\nu$. For simple radiative transfer $$\frac{dI_\nu}{dl} = j_\nu - \alpha_\nu I_\nu\ . $$ If you put an optically thin slab of ...
ProfRob's user avatar
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5 votes
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Why is Sun's energy entropy low on Earth?

It is said that we can utilize the energy from the sun on earth because it's low entropy Actually, we can utilise energy from the Sun because the temperature of the Sun is higher than the temperature ...
gandalf61's user avatar
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0 votes

Nocturnal freezing of water: Calculation of radiation through atmosphere?

With the air being very still and clear sky, the ground can radiate more heat than any possible absorption from the atmosphere above. The atmosphere up higher even in an inversion where it's warmer, ...
user415081's user avatar
1 vote

Besides the 2nd law of thermodynamics, what laws of optics prevent the temperature of the focal point of lens from being hotter than the light source?

My easiest argument was that the 2nd law of thermodynamics prevents this from happening because heat can't flow passively from a place of lower energy/entropy to a place of higher energy/entropy. He ...
Ján Lalinský's user avatar
2 votes
Accepted

Heating an object with black body radiation to above the temperature of the source

Thought experiment 1 A is a large black body at temperature $T_A$ in empty space. B is a small black body some distance away at the lower temperature $T_B$. I expect that B will gradually be warmed ...
Roger V.'s user avatar
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1 vote

When is the temperature relevant for a quantum many body system?

If the system is at $T=0$, all particles should be at the ground state and no excited state is possible. However, this is clearly not true for an arbitrary quantum system, given that if we solve ...
Roger V.'s user avatar
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0 votes

The usage of temperature in quantum mechanics

Statistical mechanics can be derived from suitable models in the decoherent limit of quantum theory. In many quantum experiments, such as single particle interference, the square amplitudes of states ...
alanf's user avatar
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1 vote

The usage of temperature in quantum mechanics

Many-body quantum mechanics is also often referred to as Quantum statistical physics, which is a more telling name in the sense that it points out that we are considering systems where one has to take ...
Roger V.'s user avatar
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1 vote

Heating an object with black body radiation to above the temperature of the source

To add to the existing answers, we can quantitatively show that $T_B$ will never exceed $T_A$ in your "Thought experiment 2" using Planck's law. The key idea is that the filter must be ...
Roger Yang's user avatar
2 votes

Heating an object with black body radiation to above the temperature of the source

While a lot of the other answers touch on the various aspects of the problem, the real reason this can't be done is more subtle. First, it's not true that you can't use sunlight to heat something to ...
A Nejati's user avatar
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1 vote

Heating an object with black body radiation to above the temperature of the source

The other answers came close but does not seem to have hammered this into you: This attenuates the longer wavelengths so that the transmitted radiation has the same spectrum as a hotter object. This ...
naturallyInconsistent's user avatar
1 vote

When is the temperature relevant for a quantum many body system?

I will write my answer by addressing some of your statements in your question, and elaborate a bit around them. You start by saying: The Hamiltonian of the system is typically of the form (expression ...
Marius Ladegård Meyer's user avatar
1 vote

When is the temperature relevant for a quantum many body system?

The question in the title, the "when" question, is basically impossible to answer. I mean, it is only when your level of precision required for whatever experiment it is you are doing, ...
naturallyInconsistent's user avatar
1 vote

Heating an object with black body radiation to above the temperature of the source

I expect that B will gradually be warmed but not to above the temperature of A. Probably not even close to it. While B is receiving some radiation from A, B will be radiating to empty space in all ...
BowlOfRed's user avatar
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1 vote

Heating an object with black body radiation to above the temperature of the source

Filtering longer wavelengths will not make the spectrum equivalent to one of a hotter object. You'll simply be cutting out the region where the colder object peaks and leaving the tails that have a ...
agaminon's user avatar
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6 votes

Does color temperature limit how much a laser of a given wavelength can heat a target?

Neither the Sun nor a laser are objects in thermodynamic equilibrium The second law of thermodynamics, which prohibits the flow of heat from a colder to a warmer object, applies to objects that have ...
Roger V.'s user avatar
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6 votes

Does color temperature limit how much a laser of a given wavelength can heat a target?

Assuming that the target is a black body. The real critical factor affecting heat transfer is emit energy per unit area described by Stefan–Boltzmann law $M=\sigma T^4$. The temperature increase ...
et al.'s user avatar
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3 votes
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Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

The other answers have hammered quite well that There is no such thing as heat inside a thing; heat is the name for the spontaneous transfer of energy due to temperature differences and so if it is ...
naturallyInconsistent's user avatar
4 votes

Does color temperature limit how much a laser of a given wavelength can heat a target?

No, your reasoning does not apply to a laser. You can use Wien’s law to relate the peak emission wavelength to the temperature of a black body emitter (a perfect absorber/emitter across all ...
FTT's user avatar
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4 votes

Does color temperature limit how much a laser of a given wavelength can heat a target?

No, it is totally unrelated. Look at the National Ignition Facility (at LLNL). It has a laser, I do not know what its frequency is (probably a small multiple of $c/1064\,$nm, but it heats a pellet to ...
JEB's user avatar
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13 votes
Accepted

Does color temperature limit how much a laser of a given wavelength can heat a target?

The argument for heating by the Sun is that if the target object is hotter than the Sun it would heat the Sun rather than the Sun heating it. We could try to apply this argument to a laser, but how ...
John Rennie's user avatar
3 votes

Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

As others have said, systems don't contain heat but contain internal energy. So, let's pretend your textbook used the correct term. To socratically answer your question -- why there is not heat ...
jwimberley's user avatar
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0 votes

Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

If we heat a fraction of a block of ice at 273 K to get some liquid water at the same temperature, and remove the source of heat, the water doesn't "fall" to its previous solid phase, ...
Claudio Saspinski's user avatar
0 votes

Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

It seems that the ambiguity here is not so much in physics as it is in mathematical logic. Buckle up! Firstly and most importantly, bravo for your effort to understand your textbook. I appreciate your ...
Saeed's user avatar
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2 votes

Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

"If there is no transfer of heat between the two bodies placed in contact, they are said to be at the same temperature, but it doesn't mean that they have equal amount of heat in them." ...
Bob D's user avatar
  • 73.7k
2 votes

Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

Heat transfer only occurs when there is a temperature difference.The heat flux 'q' s.t by$$\vec q =-\lambda \nabla T$$where $T$ is temperature and '$\lambda$' is coefficient, and if $T$ is same in ...
UnnamedUser's user avatar
1 vote
Accepted

Why does capillary in gas thermometer have a temperature and pressure gradient?

Arguably, Zemansky isn't explicating any important thermodynamic point here but instead listing possible sources of error when using a certain device associated with thermodynamics—in other words, he'...
Chemomechanics's user avatar
0 votes

Why do we say that at boiling point liquid and vapour exist in equilibrium?

What does it mean by 'vapour and liquid exist in equilibrium' and also why do they exist in equilibrium? They exist in a phase equilibrium in which the boiling point is equal to the condensation ...
Stevan V. Saban's user avatar
0 votes

Why do we say that at boiling point liquid and vapour exist in equilibrium?

Vapor and liquid can coexist in a range of temperatures, usually (under standard pressure 1atm), in range $273.15-373.15$K. When increasing temperature mentally (moving horizontally to the right on ...
Ján Lalinský's user avatar
0 votes

When does equilibrium mean accessible microstates are represented with equal probability in an ensemble of systems?

The point is that the microstates have equal probabilities, while the macrostates may have different probabilities. If the macrostate is defined by some energy property, then, for every energy, there ...
Quantum Mechanic's user avatar
0 votes

Why do we say that at boiling point liquid and vapour exist in equilibrium?

The key ingredient missing from the other discussion here is the concept of chemical equilibrium. You are entirely correct that the boiling temperature is the point at which the vapor pressure of the ...
Matt Hanson's user avatar
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0 votes

Why do we say that at boiling point liquid and vapour exist in equilibrium?

The boiling point of a liquid is the point till which the liquid and gaseous phases can coexist. A dynamic equilibrium is created. At higher temperatures, only one phase dominates. The rate at which ...
Ritesh Nandi's user avatar
-1 votes

In summer when air temperature higher than 37 degree celsius, is it better to wear more clothes to keep cool?

You produce heat by essentially burning glucose. So if you isolate yourself your temperature will keep increasing. If the air temp is lower than your body temp you cool because of second law, but if ...
Alien from future's user avatar

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