28
votes
Calculating temperature when it is lower than your thermometers can read?
The freezing point of water ethylene glycol mixtures depends in the concentration of ethylene glycol. You can find data for this on the Engineering Toolbox web site (a valuable source of all sorts of ...
- 351k
9
votes
Accepted
Why Curie temperature is bigger for smaller lattice in 2D Ising model
Why numerical simulation gives seemingly wrong result?
The exact expression for $T_c$ is given by
$$T_c=\frac{2J}{\ln\left(\sqrt{2}+1\right)}\approx 2.269\,J,$$
where we assume that $k_B=1$. This ...
- 2,464
6
votes
Calculating temperature when it is lower than your thermometers can read?
Mass of polystyrene cup + lid (with hole for thermometer) = $m_{\rm c}\,\rm g$ (assume thermal capacity is negligible)
Mass of polystyrene cup + lid + water = $m_{\rm c+w}\,\rm g$
Mass of water = $m_{\...
- 93.8k
3
votes
Accepted
How does a blackbody heat up if it emits all radiation that it absorbs?
To begin with, in real life the absorptivity and emissivity are not exactly the same as both of these things are functions of wavelength. This means it is possible for an object sitting in sunlight to ...
- 90.1k
2
votes
Water Vapour and Liquid Water Interactions
There is absolutely nothing stopping them, and in fact water molecules are constantly hopping between the phases to a degree dictated by the temperature of the system. The proper term used to describe ...
- 2,055
2
votes
Convert radiation density into temp in degrees kelvin
By using the integrated energy density of a blackbody radiation field, which is
$$u = \frac{\pi^2}{15}\frac{(k_BT)^4}{(\hbar c)^3}\ .$$
Divide this by $c^2$ to get the equivalent mass density.
- 128k
2
votes
Resistivity: related to $V/I$ or $dV/dI$?
In principle, we distinguish static and differential resistivity. The differential resistivity depends from the point on the current-voltage characteristics where we calculate the derivative, so we ...
- 57.6k
1
vote
Why expansion of real gases lead to cooling?
There are various conditions which might apply while a gas expands.
adiabatic (isentropic) expansion. Gas does work on its surroundings (pushing on the boundary as the boundary moves) so loses energy....
- 56.7k
1
vote
A bit funny practical task: frozen dumplings in boiled water, how temperature changes and when will boil again?
Assuming you have boiling water and standard conditions (T = 20°C, P = 101.3 kPa) and do not add any energy to it, it will stop boiling due to heat loss to the environment. There is no need to add the ...
- 61
1
vote
Thermodynamics and Special Relativity
What happens to the temperature of a body (not in the body frame) as it approaches the speed of light?
As discussed in this article, no one can tell you the answer, at least unless you choose a ...
- 17.6k
1
vote
Calculating temperature when it is lower than your thermometers can read?
Adding a known amount of energy via a microwave oven
Pour a known volume/mass of water into a lightweight plastic cup. Let's assume you pour 100 ml = 100 g.
Place the cup into the freezer and allow it ...
- 151
1
vote
PROOF of Only Hot to Cold Heat Transfer
The laws of thermodynamics possess a probabilistic nature: they are expected to hold on average, but there is nothing to preclude their temporary violation when we go beyond the thermodynamic limit. ...
- 1,158
1
vote
Temperature and correlation with evaporation
As mentioned in the comments, there is no reason that the temperature should remain constant as water evaporates unless it is supplied with some source of heat. In fact, since the enthalpy of the ...
- 2,055
1
vote
Second Law of Thermodynamics and heat flow
The cold water "gain" heat and the air in the dining room "loose"
heat. But, why the temperature in the dining room remain the same?
Should it be colder?
It is cooler. But the ...
- 69.1k
1
vote
Zeroth Law of Thermodynamics on Thermometer
You place a thermometer in thermal contact with system $A$ and get a "reading" $R$ on the thermometer.
As an example $R$ could be a mark at the position of the top of the mercury column in a ...
- 93.8k
1
vote
Steam from a cup of coffee
The amount of water that air can take up before the water creates fog or visible steam depends on temperature. The colder the air, the less water it needs to create fog/steam. It is the same principle ...
- 377
1
vote
Does electron have a temperature in the atom?
I have little to say about QCD, but I will try to analyse this question from thermodynamics perspective. And I think I have a decent answer.
Save Time: In essence, protons and neutrons exhibit ...
- 49
1
vote
Does electron have a temperature in the atom?
From the way the question was formulated, I deduce that some clarification on some basic concepts is needed.
If we speak of electrons in an atom, we can safely ignore physics at much larger energy ...
1
vote
Does electron have a temperature in the atom?
There is technically a way to incorporate the concept you are trying to talk about; I gave you an upvote to undo the downvotes you are getting on this question.
There is a reason why there is a ...
- 7,398
1
vote
Do there exist materials whose Opacity varies with temperature?
There are certainly materials which change colour with temperature. This behaviour is called thermochromism.
- 47.6k
1
vote
How does a blackbody heat up if it emits all radiation that it absorbs?
it emits all the radiation that it absorbs by definition?
This is not the correct definition of a black body. The Wikipedia definition of a black body says:
A black body or blackbody is an idealized ...
- 94.6k
1
vote
How does a blackbody heat up if it emits all radiation that it absorbs?
A blackbody is in thermodynamic equilibrium. It is not getting hotter or colder.
Having realised this, then it is more straightforward to understand why a true blackbody emits as much radiation as it ...
- 128k
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