Questions tagged [temperature]

It's the physical property that indicates the degree/intensity of heat present in a substance or an object. It can be expressed and measured according to various scales.

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What are the applications of materials if their entropy increases with temperature?

What could be the possible applications of the materials if their entropy increases with increasing temperature.
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Symmetry restoration at high temperature

Weinberg in his famous article https://doi.org/10.1103/PhysRevD.9.3357 discusses how finite-temperature effects in a renormalizable quantum field theory can restore a symmetry which is broken at zero ...
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Why isn't the SI unit for temperature selected so the universal gas constant is 1?

This is similar to, but not quite a duplicate, of Why isn't temperature measured in joules per mole (J/mol)? , which underspecifies Joule/mol rather than "mean disordered translational ...
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How to harvest water passivley?

I have been reading recently about methods to collect moisture from the air passively and turn it into water. However, is there any attempt currently for small-scale water harvesting? Methods I have ...
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How do you make light?

We make light making a charge oscillate, or heating a body. Are there differences between the two processes? But, above all, are there other ways in which we can produce em radiation?
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How best to maintain the temperature of a swim spa?

All the advice I have seen on the internet suggests that it is more economical to keep the thermostat of a hot-tub at its intended temperature, rather than turning down the thermostat when the tub is ...
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Inaccurate flow rate measurements of an engine diesel fuel due to change of its viscosity

I am measuring the volumetric flow rate of a diesel fuel using "Turbines" flow meter, both in the supply and return fuel lines of an industrial diesel engine (Caterpillar 3512B – coupled ...
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Why is it so much harder to keep the same room cool than to keep it warm?

I have read this question: Let me offer a different perspective on this. Cooling is not universally harder than heating. Why is cooling much harder than heating? Now I have noticed that whenever in ...
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How to find external surface temperature with unknown heat transfer coefficient?

I am trying to calculate the thickness of insulation required for a certain design. The known properties are the inside temperature, target surface temperature and thermal conductivity. From what I ...
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What does $C^{XY}_{\ell}$ mean when we weasure $a_{\ell m}$ in the sky?

In cosmology context, we have the general formula for the angular power spectrum $C_{\ell}$ : $$C_{\ell}=\left\langle a_{l m}^{2}\right\rangle=\frac{1}{2 \ell+1} \sum_{m=-\ell}^{\ell} a_{\ell m}^{2}=\...
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Slope of constant pressure line on $T$-$S$ plot

Is slope of constant pressure line is same or di in liquid region and super heated region for pure substance on $T$-$S$ diagram?
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Equilibrium temperature and phase changes

Suppose we have $M$ kg of ice at temperature $t_{ice}<0°C$ and $m$ kg of water at temperature $t_w>0°C$ that are put together in a calorimeter (so we can ignore all dispersions of heat to the ...
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What is the exact relation between the average kinetic energy of a system and temperature?

I have just started studying thermodynamics and I have been taught that the Temperature of a system is a " measure" of the Average Kinetic Energy of a system but I wonder if there is an ...
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The entropy given by stefan Boltzmann's law looks remarkably similar to the volume of the sphere; $S(T)=\frac{4}{3}\sigma T^3$

If I am not mistaken the entropy for a blackbody per unit area is given by: $$S(T)=\frac{4}{3}\sigma T^3.$$ The volume of a sphere is given by: $$ V(r) =\frac{4}{3}\pi r^3. $$ Is this coincidental? I ...
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Radial dependence of temperature for adiabatic expansion of ideal gas

If the solar wind propagates out adiabatically with a constant speed and can be regarded as an ideal gas, how the solar wind temperature depend on radial distance from the sun $r$, i.e. $T$ as a ...
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What exactly is the specific heat of a gas?

When I read that specific heat of Steam $(100 °C)$ is $2010 J/kg \cdot °C$ what exactly am I reading? What does specific heat of a gas essentially mean when it is not mentioned whether it was measured ...
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Absolute zero and zero-point energy

What will be the theoretical temperature of ideal solid state matter where all the atoms have only zero-point quantum fluctuation? Is it exactly 0.00000 K or still some 0.000000x K?
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How can the universe be hot or dense in the first moments after the big bang when it has no matter?

From the CERN website: In the first moments after the Big Bang, the universe was extremely hot and dense. I've always heard this about the big bang but I've never thought about it before now. If &...
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What's the definition of temperature ? What's the meaning of reaching a zero temperature and infinity temperature? [duplicate]

I'm taking a course about statistical mechanics and it is completely new to me . We've learned about entropy and how when 2 different sub-systems comes to contact the entropy of the whole system keeps ...
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What will happen when an object temperature rise but don't stop? [closed]

Like a substance heat in state of solids at a certain point covert into liquid, gas and plasma and my question is what will happen when we heat plasma continuously with rising temperature
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Why can't we do this to reach absolute zero?

I have seen the argument that one cannot reach absolute zero in a finite number of steps. For instance on Wikipedia, it states It is impossible by any procedure, no matter how idealized, to reduce ...
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Why exactly is there a constant temperature during condensing/freezing?

I have read many times that the reason temperature stays constant when heating a substance through a change of state is because most of the joules of energy put into the substance go into the ...
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Does the vacuum have a heat capacity ratio? Since there is nothing to 'warm' up

So the heat capacity ratio is the ratio of the heat capacity at constant pressure to heat capacity at constant volume. Since there is no pressure in the vacuum, the heat capacity ratio of the vacuum ...
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Can I use combustion gases for heating?

What is the temperature of the carbon dioxide gas released from combustion of wood? If I let the gases escape directly, then only some heat is transferred by the gas to the heating drum and the rest ...
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How can both of these versions of Wien's displacement law be correct? [duplicate]

I'm reading Bohren's "Fundamentals of Atmospheric Radiation" and I'm finding one of the points in the first chapter troubling. The author introduces Planck's distribution, both in terms of $\...
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Can you estimate vertical wind speed based upon temperature difference?

I have some data from an automatic weather station, with recordings of both $\rm 2\ m$ air temperature and $\rm 2\ m$ air pressure and also the surface temperature. Is it possible to estimate vertical ...
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Is thermal vibration a property of a particle moving back and forth by itself, or of a system of particles colliding?

When we say gas has a given temperature, it means the particles vibrate, or move back and forth, in the aggregate. Is this movement back and forth only due to each particle moving linearly and then ...
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How to calculate heat dissipation of metal box? [closed]

Lets say I have a steel cubical box of size $1$m filled with water at room ($20$°C) temperature. At first everything in box is $20$°C temperature, and then internal water heater (with power of $10$kW) ...
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What is the difference between absolute zero Kelvin and almost absolute zero? [duplicate]

Scientists say that it is impossible to reach a temperature of zero kelvin, because the atoms will stop moving, and the volume of the substance will become zero, But we have reached the pico kelvin ...
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Is this floating ship really a mirage? [duplicate]

The media is full of stories of rare pictures of flying ships. They go on to describe them as mirages. These images are described as rare. The picture I have uploaded was taken on Good Friday 2022 ...
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Heating things with a lens. Theoretical limit vs. energy conservation

Recently I've heard that you can't heat up stuff beyond sun's surface temperature using sun+lens combination. It is because you can't transport heat from colder object to a hotter object. Of course, ...
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Ideal Fermi gas close to $T=0 \rm K$

I am reading about the behaviour of ideal Fermi gas close to $T=0K$ from Kardar's Statistical Mechanics. In the paragraph which I have highlighted, we have the inyegral representation of $f_m^{-}(z)$....
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Deriving Wien's approximation

Without Planck's law from where and how could one empirically get this. Could it be got from power is proportional to fourth power of temperature.
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High temperature limit of ideal quantum gas

I am reading ideal quantum gas from Kardar's Statistical Mechanics. $VII.35$ is the representation of pressure, number density and energy density in the form of $f_m^{\eta}$. $z=e^{\beta\mu}$ where $\...
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Doesn't the thermodynamic definition of temperature imply the existence of exotic systems with negative temperatures?

The thermodynamic definition of temperature is simply: $$T=\left(\frac{\partial{U}}{\partial{S}} \right)_{V,\ n}$$ As you see there is no absolute value involved. This implies that the partial ...
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How long does it take, and how much heat, to raise the temperature of air in a box?

I am seeking to crudely model a house with a window as a perfectly insulated box with a hole (which only allows radiative heat). My question is to find how the temperature of air in the box changes ...
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Why does water collect under a book my laptop is sitting on?

Sometimes I sit in my bed with a blanket over my lap. On top of the blanket I put a hardcover book. On top of the book I will be working on my laptop. So we've got: Laptop Book Blanket My lap ...
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Is zero-point energy the real reason behind zero Kelvin being impossible to reach?

I am aware that the third law of thermodynamics entails an infinite number of steps if one wants to bring down the temperature of a system to $0$ K. I understood this to be a classical telling of a ...
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What happens to a quantum harmonic oscillator at $T = 0$?

Say I have two identical non-interacting particles of spin $\frac{1}{2}$ and masses $m$ in a harmonic potential with constant $k$. What would be the average kinetic energy of the gas at $T=0$? What is ...
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Is the statement $dF=(\delta Q-TdS)-pdV-SdT$ more general than $dF=-SdT-pdV$?

So the Helmholtz free energy is defined as $F=U-TS$, which means $$dF=\delta U-TdS-SdT$$ $$=(\delta Q-pdV)-TdS-SdT$$ $$=(\delta Q-TdS)-pdV-SdT.$$ since $\delta Q \neq TdS$ ($dS \geq \delta Q/T$) in ...
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Defining Temperature [duplicate]

I have learnt the definition of Temperature as Temperature is defined as the average of Kinetic energy of the particles in the Object. My doubt is can't we measure the temperature near the sun as ...
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Why are single-electron states occupied at $T=0$ in superconductors?

Some textbooks show a density of states where the single-electron states below the Fermi energy are occupied at $T=0$ (see picture). However, I thought that at $T=0$ all electrons are paired. Hence ...
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Green function dependence on temperature

Consider the retarded Green function for fermions $$ G_{ij}^r(t)=-\frac{i}{\hbar} \theta(t)\langle[c_i(t),c^\dagger_j(0)]_{+}\rangle $$ They can be understood as the $(i,j)$ entry of the matrix $G^r(t)...
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A question regarding dropping a penny in liquid nitrogen (Leidenfrost Effect)

If I drop a penny in an insulated cup with liquid nitrogen there is a layer of nitrogen gas between the penny and liquid and thus the penny cools slower than usual as stated by the Leidenfrost effect. ...
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I’m studying black body radiation and I can’t understand how it produced due to the vibrations of atoms

So,in my physics school book it’s written that atoms don’t radiate as long as they are stable ”in the ground state” I can’t understand how I mean isn’t all the bodies radiate as long as they have a ...
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Einstein coefficients cannot depend on temperature?

I am looking at the Wikipedia article on the Einstein coefficients. There is this line about the detailed balance condition to hold at all temperatures. Why is it that the Einstein coefficients ...
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Proving Relationship between Statistical Weight $Ω$ and Partition Function $Z$

How can I prove that $$\frac{\partial(T \ln Z)}{\partial T}=\ln \Omega,$$ without using the relation $S=k\ln Ω$? where $Z$ is the Partition Function, $T$ is the Absolute Temperature, $Ω$ is the ...
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Do we have a "good" model for the temperature of the Earth's crust/mantle/core measured from the center of the earth?

Is there a "good" function $f$ that models the temperature of the Earth's crust/mantle/core measured $r$ miles from the center of the earth? By good, I mean a function that strikes a nice ...
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Why is $TΔS$ a good approximation for calculating heat transfer during heating/cooling in real life?

So various books and sources have agreed on defining specific heat capacity (formally) to be: $$c_v=\frac{T}{n}\left(\frac{\partial S}{\partial T}\right)_V=\frac{1}{n}\left(\frac{\delta Q_{reversible}}...
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What is the distribution on the speed of particles in a liquid? (analogous to the Maxwell-Boltzmann distribution)

I know, for gases, the distribution on the speed of particles is the Maxwell-Boltzmann distribution. What is the corresponding distribution for liquids (e.g. water)? You can assume that the liquid is ...
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