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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2answers
3k views
Does tea stay hotter with the milk in it?
A little thought experiment, similar to this one: Imagine you are making a cup of tea when the door bell rings. You've poured the boiling water into a cup with a teabag in it. As you're just about to ...
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1answer
240 views
Why does an infrared thermometer display very low temperature when being directed to the outer air?
I'm toying with an infrared thermometer - one which you point onto an object, press the button and it instantly measures the temperature by estimating the infrared radiation from the object. It shows ...
5
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4answers
1k views
Why less temperature at high altitude
Why there is always cold at high altitudes. e.g. at peak of mountains. Also as we go high from see level, temperature starts decreasing, so why is it.
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2answers
55 views
Statistical Weighting Factor on thermal neutron importance
The problem is concerning the use of a thermal fluxed squared weighting factor in a thermal reactor.
I have seen in sources the thermal flux in a reactor is squared as a statistical weighting factor, ...
4
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1answer
130 views
Ideal gas and diatomic gas with same temperature
If a box of ideal gas and another box of diatomic gas are in thermal equilibrium,
does it mean that the average translational energy of ideal gas particle (A) is the same as that of diatomic gas ...
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0answers
48 views
Martian ground exchange heat pump
According to the wikipedia article Geothermal heat pump, "Depending on latitude, the temperature beneath the upper 6 metres of Earth's surface maintains a nearly constant temperature between 10 and 16 ...
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1answer
244 views
Why there is no negative temperature [duplicate]
Possible Duplicate:
Prove that negative absolute temperatures are actually hotter than positive absolute temperatures
Proof of existence of lowest temperature $0 K$
On the Kelvin ...
11
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3answers
863 views
Prove that negative absolute temperatures are actually hotter than positive absolute temperatures
Could someone provide me with a mathematical proof of why, a system with an absolute negative Kelvin temperature (such that of a spin system) is hotter than any system with a positive temperature (in ...
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0answers
96 views
“This is not a perpetual motion machine, because reservoir temperatures are changing.” Is it a valid argument?
I've already faced this situation several times: given a statement (in area of thermodynamics) I used it to provide an example of some perpetual motion machine (of first or second kind). Therefore, I ...
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2answers
687 views
Does negative temperature in Carnot cycle yield a counterexample of the second law of thermodynamics?
By Carnot Theorem, the efficiency of Carnot cycle is$$\eta=1-\frac{T_C}{T_H}$$
where $T_C$,$T_H$ are the absolute temperature of the cold reservoir and hot reservoir respectively. Since $T_C > 0$, ...
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1answer
1k views
Ideal gas law, pressure increase and temperature
If I had a container, full with air, and I suddenly decreased the volume of the container, forcing the air into a smaller volume, will it be considered as compression, will it result in an increase in ...
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1answer
3k views
Why does a gas get hot when suddenly compressed? What is happening at the molecular level?
My guess is that the molecules of gas all have the same speed as before, but now there are much more collisions per unit area onto the thermometer, thus making the thermometer read a higher ...
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2answers
173 views
What happens when atoms speed up to extreme velocity?
The title might be misleading, but my question is in regard to what happens when we reach temperatures close to absolute zero (Kelvin). I've found different quotes as to what happens on the low end of ...
3
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3answers
323 views
How do Temperature Scales work?
How exactly do temperature scales work?
If my understanding is correct, the Celsius scale has two fixed points: (definitions of temperature irrespective of scale)
1. The freezing point of pure water ...
2
votes
3answers
136 views
Heat Equation Equalities
While studying the heat equation, I ran into a few equalities that I cannot understand.
For example, Fourier's law of heat conduction claims that
$$\varphi(x,t)=-K_0\frac{\partial u}{\partial x},$$
...
4
votes
1answer
68 views
Where does the heat flow in the Earth's crust switch from primarily solar to geothermal?
Ok, maybe more of a geology question than physics, but maybe somebody has been involved in modeling these heat flows?
Essentially I'm asking if we know what sort of depth the heat source becomes ...
4
votes
3answers
4k views
How can I calculate Vapor Pressure Deficit from Temperature and Relative Humidity?
I have a series of measurements of temperature and relative humidity (RH), together with mosquito capture data. Because mosquitoes are sensitive to desiccation, it's reasonable that RH may be useful ...
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1answer
115 views
How do the energy eigenvalues of rotational degrees of freedom in statistical mechanics come about?
I want to understand the hierarchy different degrees of freedom of a mechanical system. Specifically, I want to understand which subsystems equibrilate faster and why. This question comes up:
Why ...
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1answer
250 views
How to calculate Temperature Humidity Wind Index?
I would like to know how to calculate Temperature Humidity Wind Index (THW Index)? I know how to calculate Heat Index and Wind Chill. I am asking this because my weather station Davis Vantage Pro2 ...
3
votes
1answer
201 views
Local Mach number for an airfoil
I would like to know how to calculate the local Mach number on the upper surface of an airfoil given the ambient temperature, the local velocity on the airfoil surface, the freestream velocity, and ...
11
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4answers
6k views
Why does the air we blow/exhale out from our mouths change from hot to cold depending on the size of the opening we make with our mouth?
Why does the air we blow/exhale out from our mouths change from hot to cold depending on the size of the opening we make with our mouth?
It's not just a subtle difference, but significant in my ...
4
votes
3answers
436 views
Is temperature an extensive property, like density?
I was thinking about it some time ago, and now that I've discovered this site I would like to ask it here because I couldn't work it out then.
I know that the higher temperature the air in my room ...
1
vote
2answers
138 views
Using CO2 to air condition a room
I'm trying to determine how much dry ice or liquid nitrogen I would need to cool 3300 cubic feet, about 90,000 liters of air, from about 100F (37.78C or 310K) to about 90F (26.67C or 299.81K). I'm ...
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1answer
140 views
Calculating temperature of water in the freezer
Assuming water volume ($V$), initial water temperature ($T_0$) and environment temperature ($T_e$) are known, what is the easiest way to calculate temperature of water in given time ($T$)?
For the ...
0
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3answers
376 views
Units of Distance, Pressure, and Temperature [closed]
I need to store data.
I'd like to store them in Metric units and use a tool to convert them to and from other units that these data points will be displayed in.
As the title states, my constraints ...
2
votes
1answer
113 views
Is it possible to use a powder-based firearm in space?
A firearm relies upon some kind of explosive powder to drive the slug out of the barrel.
My guess however is that in space (at GEO, or higher) a firearm would be unusable due to the extremes of ...
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1answer
104 views
Temperature and latent heat
Building a bronze stature we make a mold and pour in the liquid bronze when the bronze hardens we remove the mold.
The mold is made of 3 Kg of steel and the statue has a mas of 1 Kg. The specific ...
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votes
2answers
1k views
Why I will feel colder when I get out from a swimming pool?
A friend of mine told me that because water heat capacity is higher. He also mentioned that it was similar to alcohol on skin effect.
Assume that there are 3 situations.
1. I did not get wet
2. I got ...
2
votes
1answer
223 views
Why does blowing on someone who is wet feel colder than on someone who is dry?
The title says it all. If I'm standing in the wind and I'm wet, I feel much
colder than when I'm dry. This is true no matter how warm or cold the water.
Why is this?
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3answers
220 views
How Is It Possible To Measure Extreme Temperatures? (>2M Deg)
Linked Article: Fusion: X-ray laser zaps solid to 2 million degrees
The quest to create nuclear fusion may have come a step closer when scientists heated solid matter to two million degrees with ...
0
votes
2answers
473 views
Why is the temperature outside the airplane lower than the ground temperature?
seems the airplane is nearer to the sun, so the sun should more directly shine on the plane. But when I travel, the airplane temperature is much lower than the ground. Why is the temperature so low?
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votes
1answer
784 views
Using resistance and temperature coefficient formula
What is the correct way to use the resistance and temperature correlation formula from http://hyperphysics.phy-astr.gsu.edu/hbase/electric/restmp.html?
In particular, does R have to be the higher ...
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0answers
234 views
How to liquefy Hydrogen?
I have got a science project and my teacher has recommended me to do "Liquefying Hydrogen". I have been continuously thinking about that but I have not come to a solution. Can anyone please tell me ...
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5answers
852 views
How do we perceive hotness or coldness of an object?
Some objects, especially metallic ones, feel cold on touching and others like wood, etc. feel warm on touching. Both are exposed to same environment and are in their stable state, so some kind of ...
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2answers
204 views
Do you pay more for gas when the day is warmer?
Found this at the gas station yesteday - got me thinking...
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1answer
86 views
What is a good reference for the mechanical properties of materials at cryogenic temperatures?
I want to research various the properties of various materials, namely tensile strength at cryogenic temperatures (~20K). I was wondering if a freely available database of material properties exists.
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1answer
460 views
How are the CPU power and temperature caculated/estimated?
From Wikipedia
The power consumed by a CPU, is approximately proportional to CPU
frequency, and to the square of the CPU voltage: $$
P = C V^2 f $$ (where C is capacitance, f is ...
3
votes
3answers
331 views
Proof of existence of lowest temperature $0 K$
Im mathematics there is a concept of infinity meaning that whenever you pick a number and say that it is the smallest/Largest there is a way to further reduce/increase that number by ...
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1answer
78 views
If the temperature of 2 materials are the same does that mean the molecules are vibrating at the same speed?
Pretty much what the title says. My base question is this. Assuming I take a piece of steel, and a piece of PVC plastic and I measure both their temperatures and find they are the same. I then take a ...
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3answers
354 views
Opposite of Cryogenics
Cryogenics is related to very low temperatures, so, what is the term when referring to very high temperatures?
4
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1answer
492 views
The speed of sound is proportional to the square root of absolute temperature. What happens at extremely high temperatures?
The speed cannot increase unboundedly of course, so what happens?
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4answers
1k views
What kinds of materials contract the most in cold temperatures?
I know that water expands in the freezer, but I'm curious about which materials contract in response to cold temperatures --- and most importantly, which ones undergo the most drastic changes?
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1answer
210 views
Thermodynamics, bullet fired into ice
I'm beginning to study basic thermodynamics and I want to solve this exercise:
It fires a lead bullet from $3g$ to $30^oC$ with a speed of $240\frac{m}{s}$ to a block of ice at $0^0C$. How much ice ...
0
votes
1answer
151 views
Mixing Water at Different Temperature
If I have cup of water at room temperature (say, $25^\circ$C). What would be the resultant temperature if I pour another cup of same amount of water at $100^\circ$C to it? Is it simply ...
4
votes
2answers
1k views
How to calculate the evaporative cooling rate needed to protect a house from forest fire
Recently in our area there has been a large forest fire and I've been looking into home defense from such things.
I am not a physicist - but can do some basic math.
I was wondering how I could ...
1
vote
2answers
453 views
Colour emitted at a specific temperature (color temperature?)
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 ...
4
votes
4answers
1k views
Light emitted by an object according to its temperature
According to this picture
the light emitted by an object depends on its temperature.
That makes perfect sense when we heat a metal. As its temperature raises we see it red at first, then orange, ...
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vote
2answers
520 views
How do we determine the temperature of a Black Hole?
How do we determine the temperature of a Black Hole?
Since we cannot see a Black Hole, which I presume, is because it absorbs light, would it not also prevent radiation from escaping, making ...
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vote
1answer
129 views
what will happen when I continuously heat a closed heavy iron box half-filled with water?
I mean what will be the situation inside? All water vaporized, Equilibrium, Temperature-pressure situation.. boiling point increase/decrease?
Thanks for your time.
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1answer
462 views
Inductor with controlled temperature coefficient
Let's assume we have an air-spaced inductor made of copper wire.
As temperature changes, due to thermal expansion of physical dimensions of the coil, its inductance changes too.
1) Is there a way to ...
