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.
5
votes
4answers
148 views
Can a single molecule have a temperature?
A show on the weather channel said that as a water molecule ascends in the atmosphere it cools. Does it make sense to talk about the temperature of a single molecule?
1
vote
1answer
56 views
Electromagnetic field to cool a substance?
I saw somewhere that an electromagnetic field would cause a substance to let off thermal energy, ultimately resulting in the substance to cool really quickly.
If this is possible, does the strength ...
3
votes
2answers
467 views
Are Colors Emitted at Specific Temperatures?
There are quite a few nagging questions I have been having over the years, I do not require a full explanation, just some guidance in my assumptions and pointers if I am very wrong.
My basic ...
2
votes
2answers
120 views
Why is the temperature zero in the ground state?
This is probably a simple question: I see this claims in many books, but I can't figure a reason why this is true.
So my question is why this claim is true:
"If we know that the system is in the ...
2
votes
3answers
125 views
What is the general statistical definition of temperature?
Temperature in an isolated system is defined as:
$$\frac{1}{T} = -\frac{\partial{S(E,V,N)}}{\partial{E}} $$
But I wonder how one can generalize this to a random system.
Or for instance to a point in ...
2
votes
2answers
26 views
How would a change in ambient temp affect a radiator?
I'm curious if you have a radiator or say a block of metal (lets say it's copper since it has the highest thermal conductivity) and on one side is a processor producing heat.
At idle the processor ...
0
votes
2answers
24 views
High and low pressure area and raining
In the high-pressure area it is mostly likely that there is sun. In low pressure area it is mostly likely that rain will occur.
Because of the law that ...
1
vote
1answer
75 views
Does brown but transparent swimming pool water heat significantly faster than western style highly chlorinated pools?
Eastern European swimming pools are often brown tinted water. i was told it was the color of the chemical to keep the pools clean, but who knows. These pools did not smell unsanitary and may have even ...
0
votes
1answer
217 views
How much energy Maxwell's demon will earn?
Suppose we have one mole of one-atom ideal gas at temperature $T$.
Suppose Maxwell's daemon has separated molecules into two sections, one with speed below mean and another with speed above mean.
...
2
votes
2answers
57 views
What is the derivation for the exponential energy relation and where does it apply?
Very often when people state a relaxation time $\tau_\text{kin-kin}, \tau_\text{rot-kin}$,, etc. they think of a context where the energy relaxation goes as $\propto\text e^{-t/\tau}$. Related is an ...
1
vote
1answer
26 views
Speed of air through valve
Right now I'm working on a hot air balloon in Physics formulas. At the moment it's flying up like it should, but once it is at a certain height we want it to go back down.
After some research about ...
1
vote
0answers
28 views
Can I maintain a constant relative humidity using saturated salt solution, at greater than atmospheric pressure? [migrated]
At atmospheric pressure and between temperatures of $\sim 0$ to $100^\circ C$, well known relationships between established humidity and given saturated salt solution are available. I.e. ASTM E104 ...
0
votes
0answers
22 views
Removing seasonal and non-seasonal oscillations with least-square method [closed]
I was trying to find help online, but with no luck :( Hoping you will help me!
I have data containing sea temperature with depth. With data I need to remove seasonal and non-seasonal oscillations by ...
5
votes
1answer
42 views
Reflectivity of a glowing-hot metal surface
When a polished piece of metal (or steel in particular) is heated to incandescence, how do its reflective properties change?
Given a mirror-like surface, would the object temporarily cease to act ...
0
votes
0answers
17 views
What is the effect of an increase in pressure on latent heat of vaporization?
What is latent heat of vaporization ($L_v$) in the first place? Wikipedia seems to indicate that it is the energy used in overcoming intermolecular interactions, without taking into account at all any ...
1
vote
1answer
70 views
Ginzburg-Landau model for superconductivity
Could someone kindly elaborate more on the Simple Interpretation section from this Wikipedia Article? I refer to the part on the natures of $\alpha , \beta$. Why can one assume that ...
1
vote
0answers
53 views
Calculate how hot PLA will become
I am trying to attach the shaft of a brass heating tip to a PLA component. My problem is that the tip will have to reach a temperature of about 200°C and the PLA can only handle a temperature of about ...
3
votes
2answers
177 views
Ideal gas concentration under temperature gradient
I'm trying to calculate the concentration of an ideal gas in an adiabatic container as a function of position where the top and bottom plates of the container are fixed at temperatures $T_1$ and ...
1
vote
1answer
59 views
How long does it take a warm object to cool in air?
This is a work-related question. A warm steel torus of a given diameter & thickness is left in a room held at a controlled temperature, how long does it take to reach equilibrium? Assume the air ...
2
votes
1answer
41 views
Temperature of a small system
What is wrong if I define temperature of a small system (I mean, a system which has not a large number of particles) by
$$1/T = dS/dE$$
?
0
votes
1answer
48 views
Negative temperature and Absolute hot
This video explains that heat at negative temperatures flows from the negative object to the normal object. If the temperature of the normal object is absolute hot, what happens with the heat? The ...
4
votes
1answer
32 views
Is there a naturally occuring sound pressure level reference?
There are lots of devices that purport to measure the absolute value of sound pressure levels. Here is an example, here's another, there's also this iPhone App. Putting such devices side-by-side in ...
-1
votes
1answer
45 views
Heisenberg's uncertainty and $0 K$ temperature
when a body is subjected to $0 K$ temperature, it becomes rigid. hence if we see in terms of quantum the lattice vibration decreases, resulting in no change in the direction of the Random velocity, ...
1
vote
3answers
132 views
Integrating factor $1/T$ in 2nd Law of Thermodynamics
How would you prove that $1/T$ is the most suitable integrating factor to transform $\delta Q$ to an exact differential in the second law of thermodynamics:
$$dS = \frac{\delta Q}{T}$$
Where $dS$ is ...
0
votes
2answers
110 views
How can anything be hotter than the Sun?
I've heard that if a space shuttle enters the atmosphere from a bad angle its surface will become so hot that it will be hotter than the surface of the Sun.
How can that be? It seems to an uneducated ...
0
votes
0answers
30 views
Negative temperature [duplicate]
How can we prove that if a negative-temperature system is in contact with a positive-temperature system, then the heat flow from the first to the second (and finally, the temperature of the second ...
0
votes
1answer
65 views
How to understand the thermal radiation?
I am studying the thermal radiation (Stefan–Boltzmann law) by myself
$$P = \epsilon \sigma A T^4$$
here $\epsilon$ is the emissivity, $\sigma$ is Stefan-Boltzmann constant, $A$ is the surface area ...
1
vote
1answer
43 views
Is it physically meaningful to talk about the 'total temperature' of an object?
If I had a semi infinite, 1-D object and a finite 1-D object, both heated at the same constant rate at one end each for the same time period and both begin at the same initial temperature, is it ...
0
votes
2answers
92 views
How temperature gradient is a vector?
Everyone knows Temperature gradient is a vector quantity having direction from cold to hot.My confusion: why is temperature gradient vector if its direction is always fixed (as in the case of ...
1
vote
2answers
28 views
Heating and Recooling of an Object
Consider a piece of metal of length $L$ and linear thermal expansion coefficient $\alpha$. We eat the metal $\Delta T$ degrees, causing the metal to increase to length
$$ L' = L + L \alpha \Delta T$$
...
1
vote
1answer
92 views
Does gravity affects temperature reading of a mercury thermometer?
I remember when I was in primary school, the science teacher put me in charge of a mercury thermometer. I do not quite understand the mechanics behind except that mercury expands when it is hot and ...
16
votes
6answers
1k views
Why isn't temperature measured in Joules?
If we set the Boltzmann constant to $1$, then entropy would just be $\ln \Omega$, temperature would be measured in $\text{joules}$ ($\,\text{J}\,$), and average kinetic energy would be an integer ...
4
votes
0answers
132 views
How do I measure the temperature of a tiny water droplet?
How do I accurately (+/- 0.1 degrees Celsius or better) measure the temperature of a small (5 to 50 microliter) water droplet without noticeably affecting its temperature?
The mass of a thermistor or ...
4
votes
2answers
83 views
How hot would space feel?
I read that the temperature of the space around the earth can vary greatly depending on whether or not it is in direct sunlight. Space, however, is not very dense, so I imagine that heat would not ...
2
votes
1answer
791 views
What are the temperatures of objects in Low Earth Orbit (LEO)?
What is the temperature of objects in Low Earth Orbit?
Consider LEO to be 600km to 800km.
36
votes
5answers
4k views
How long can you survive 1 million degrees?
I asked my Dad this once when I was about 14, and he said that no matter how short the amount of time you were exposed to such a great temperature, you would surely die. The conversation went ...
3
votes
2answers
146 views
What's the basic difference between heat and temperature?
Temperature is usually seen as a calibrated representation of heat but what about latent heat?
Eg. Ice and water have different amounts of heat at 0 degree c.
3
votes
2answers
174 views
What's the avarage temperature of the Universe?
I'm sorry if this was asked before but with all the stars and dark matter and all the other stuff, curently in the Universe, what's the avarage temperature of the Universe? Is it like extremely high ...
8
votes
3answers
262 views
Could temperature have been defined as $-\partial S/\partial U$?
When coming up with a definition of temperature, it's typical to start with an empirical definition that a system with a hotter temperature tends to lose heat to a system with a colder temperature. ...
0
votes
0answers
50 views
Temperature of an Object in Space [closed]
Rotating cylinder in space
Hi all
I've been having problems trying to calculate the temperature of an object in space, and was hoping I could get some help. Say we have a cylinder in space rotating ...
5
votes
6answers
2k views
How is gradient the maximum rate of change of a function?
Recently I read a book which described about gradient. It says
$${\rm d}T~=~ \nabla T \cdot {\rm d}{\bf r},$$
and suddenly they concluded that $\nabla T$ is the maximum rate of change of $f(T)$ ...
1
vote
0answers
43 views
How to solve state parameters using these givens for an ideal gas?
In a thermodynamic turbine using air as an ideal gas, given that you have a known inlet temperature value $T_i$, a known exit pressure value $P_e$, a known inlet and exit velocity $V_i$ and $V_e$, a ...
2
votes
2answers
134 views
Why the temperature is getting lower when the universe is expanding
As we know, if an ideal gas expands in vacuum, as its energy is unchanged, the temperature remains the same. An ideal gas's energy does not depend on volume. In general, the energy is $kT$ times the ...
2
votes
1answer
138 views
Does an object's color change its rate of cooling?
The motivation for this question comes directly from this thread. The proposition is that the color of something changes how fast it cools (note: specifically the rate of cooling, not taking into ...
0
votes
2answers
351 views
What is the physical or mathematical meaning of the Gibbs-Duhem equation?
The Gibbs-Duhem equation states
$$0~=~SdT-VdP+\sum(N_i d\mu_i),$$
where $\mu$ is the chemical potential. Does it have any mathematical (about intensive parameters) or physical meaning?
1
vote
1answer
128 views
Absolute zero and Heisenberg uncertainty principle
I got to read Feynman vol I and there was written that at absolute zero, molecular motion doesn't cease at all, because if so happens, we will be able to make precise determination of position and ...
2
votes
4answers
604 views
What does third law of thermodynamics tell us?
I just have a question concerning the third law of thermodynamics.
The third law describes that the entropy should be a well defined constant if the system reaches the ground state which depends ...
2
votes
7answers
3k views
Why does the gas get cold when I spray it?
When you spray gas from a compressed spray, the gas gets very cold, even though, the compressed spray is in the room temperature.
I think, when it goes from high pressure to lower one, it gets cold, ...
7
votes
4answers
782 views
Why doesn't air freeze?
I am in no way experienced in the Physics field so this question may seem a bit silly but i'd appreciate an answer :)
Why doesn't air freeze?
4
votes
1answer
98 views
Does the Kelvin have a rigorous definition?
From Wikipedia:
The kelvin is defined as the fraction 1⁄273.16 of the thermodynamic temperature of the triple point of water.
That presupposes that we can take a fraction of temperature.
Now, ...
