Questions tagged [heat-conduction]
244 questions
71
votes
3 answers
Why does a lot of water vapour come suddenly after the heat source of boiling water is removed?
I have noticed this several times. When I am boiling water, a few seconds before its boiling point, vapours are formed as usual. But if I turn the gas off before boiling, the moment it turns off, I see a lot of vapours being formed all of a sudden…
Abha Vishwakarma
- 741
42
votes
7 answers
Bush fires and heat waves, the real mechanics?
Like many others, I have been following the sad development of the bush/forest fires in Australia recently. A claim that gets repeated is that one of the contributors to this blaze is the ongoing >45°C heatwave.
Now I am not really putting this in…
Elmore
- 616
42
votes
5 answers
Why does wrapping aluminium foil around my food help it keep warm, even though aluminium is a good conductor?
Aluminium being such a good conductor, how is it possible that it is helping me keep my food warm ?? Because ultimately it should conduct the heat that is inside to the outside for exchange and should have no effect (maybe even cool it faster by…
user235329
21
votes
4 answers
Can you model cold as flowing?
Obviously, cold isn't a "Thing".
Coldness is the absence of heat, and when you add a cold ice-cube to a drink there are no particles of "coldness" flowing into the rest of the drink cooling it down - the heat of the rest of the drink (in the form of…
Brondahl
- 670
21
votes
2 answers
Why doesn't a mercury thermometer follow the rules of volume dilatation?
let's consider a classic mercury thermometer.
I do not understand why it does not behave like a "normal" thermometer which exploits volume dilatation. In a normal thermometer, I'd say that the mercury length would be proportional to its…
Kinka-Byo
- 1,339
12
votes
5 answers
Physical meaning of potential in heat equation
I'm working on the mathematical theory of parabolic equations. The prototype of such equations is heat equation given as follows :
Let $\Omega$ be a bounded region of the space and $T>0$ a fixed time. In $\Omega_T=(0,T)\times \Omega$ we consider the…
S. Maths
- 223
11
votes
4 answers
Why would frozen sausages defrost faster in water?
My mom uses frozen sausages for a soup. She defrosts frozen sausages by submerging them in water (room temperature I believe). She claims this makes them defrost faster. She learned this from some article in a magazine and now swears by it. She is…
S. Rotos
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9
votes
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Is there a difference in the 'quality' of a gas if it's heated by electromagnetic radiation as opposed to conduction/convection?
According to this link, "The wavelength at which the $O_2$ molecule most strongly absorbs light is approximately $145$ nm."
According to this link, that's in the ultraviolet range of the electromagnetic spectrum.
Consider two tanks containing oxygen…
Cloudyman
- 1,293
9
votes
2 answers
Inverting the heat equation
I have a wire that stretches from $x=0$ to $\infty$. The temperature at $x=0$ is given by the unknown function $f(t)$ for $t$ from $-\infty$ to now ($t=0$).
I can measure the temperature of the wire at each point now ($t=0$), $g(x)$.
Given the…
Peter A
- 610
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7
votes
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Is there a name for this phenomena that I observed?
I wish I had recorded this, but I was about to get some water from my filter as I was thirsty, but I noticed it had frozen in my refrigerator, so I poured some water into it from the refrigerator, and the ice started melting incredibly fast compared…
Anders Gustafson
- 2,071
7
votes
2 answers
Heating cup in microwave?
I heated my milk cup in the microwave today and noticed that the cup was hot but not the handle. Even if I heat it too much , cups handle temperature remains the same. How is that possible?
user277437
6
votes
4 answers
How are "cold sparks" possible?
At raves, nightclubs, and parties, sometimes there are "cold fireworks" machines that spew out a dense bunch of really bright sparks. The odd thing is that these machines are apparently safe to use indoors and, even more surprisingly, have sparks…
KF Gauss
- 8,314
6
votes
2 answers
A question about thermal conductivity and heat transfer
Put a piece of cold pizza on top of a sheet of aluminum foil and then stick it in the oven to heat up. After about 10 minutes, the pizza should be nice and hot—the aluminum foil is the approximately the same temperature. You can pull the aluminum…
Swayam Jha
- 473
6
votes
5 answers
If steam and water, both at 100 °C, were exposed to a person's skin for a small time interval, which would result in a more severe burn?
Imagine that you had two boxes with of steam and water of equal mass, both at $100~^\circ\rm C$, and you decide to expose your left land to the steam and your right to the water for a short period of time. Which hand would 'feel hotter' (i.e if you…
E7_82_8E
- 137
5
votes
9 answers
Can heat(?) flow from a cold object to hot object?
When we dip a spoon (stainless steel) into ice cream, does it becomes cold or stay the same temperature? If it does, can we say that heat(?) can flow from cold to hot objects?
Is this the reason that we are given wooden(or plastic) spoons to eat…
