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31 votes

Why is rock or metal often cold to the touch but wood or plastic is not?

What we perceive as an object being "hot/ cold to the touch" is related to the rate at which heat is transferred from the object to your hand. In the case of touching an object with your ...
Nic Christopher's user avatar
25 votes
Accepted

Why is rock or metal often cold to the touch but wood or plastic is not?

In a room at normal room temperature, certain materials, such as metal, glass, ceramic, or rock, will feel cold to the touch, but others, such as wood or plastic, do not so much. When you touch ...
Bob D's user avatar
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22 votes
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Why haven't we found thermal superconductors?

In an electrically insulating crystaline solid, heat is mostly transferred by phonons rather than by photons. What provides thermal resistance is phonon scattering via impurities or umklapp ...
mike stone's user avatar
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21 votes

Can the temperature of a steel ladle in boiling water exceed the temperature of the water?

The second law of thermodynamics says (among other formulations) that heat flows from high temperatures to low temperatures, but never the other way around. In your illustration, you have the ladle in ...
rob's user avatar
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14 votes
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Can a tea light really heat a greenhouse?

"a greenhouse in the winter does not retain heat well" This is the crucial point: the rate of heat loss will be roughly proportional to the temperature difference between the inside of the ...
Philip Wood's user avatar
14 votes

Can people feel the low heat radiation from very cold surfaces?

Yes they will feel the coldness, but it's the lack of heat radiation, not radiating coldness. Essentially, the scientist's body is radiating more heat than it is receiving, and it is this difference ...
BaddDadd's user avatar
  • 513
13 votes
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Can land breezes be an example of perpetual motion?

This is not an example of perpetual motion. Both kinds of wind are driven by temperature differences (the trade winds by temperature differences between different latitudes, which in turn are caused ...
Sebastian Riese's user avatar
11 votes

Can the temperature of a steel ladle in boiling water exceed the temperature of the water?

The pot as it is in contact with the fire can have hot spots, however, the water is at a temperature of $100^\circ$C. If the ladle is completely surrounded by boiling water, then the ladle will ...
Albertus Magnus's user avatar
8 votes
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Should I hold a baby formula bottle to cool it down faster?

Sure! I think I'm qualified to answer, not because I used to teach heat transfer in a Chemical Engineering course, but because I raised four daughters!! Air is an excellent thermal insulator. If you ...
Alfredo Maranca's user avatar
7 votes

Can the temperature of a steel ladle in boiling water exceed the temperature of the water?

There will of course be a temperature gradient along the ladle, and near the surface the temperature of the ladle will be cooler than the water temperature. Steel is a good conductor of heat and some ...
Rich's user avatar
  • 1,045
6 votes

Cup of warm water suspended in a pot of water held at a steady boil

The illustration here is enlightening. The vapor bubbles form at the bottom of the pot, where the temperature of the heat source exceeds 100°C, as is required in practice for boiling*. As they float ...
Chemomechanics's user avatar
5 votes

Can the temperature of a steel ladle in boiling water exceed the temperature of the water?

In order to get to the actual question, let's assume you didn't mean 100°C but the actual boiling temperature, which will differ somewhat with time (because the atmospheric pressure varies with the ...
Peter - Reinstate Monica's user avatar
4 votes

Cup of warm water suspended in a pot of water held at a steady boil

Just reaching the boiling temperature is not enough for boiling. Boiling happens when the the vapour pressure becomes equal to atmospheric pressure. When the temperature of $100ºC$ is reached then too ...
gobbledy-gook's user avatar
4 votes

Cup of warm water suspended in a pot of water held at a steady boil

I don't have the rep to add to the above answer. But FYI I did attempt this experiment IRL and can say that the temp in the cup never got much above 90 deg C. I did leave it at a rolling boil for 10 ...
Rewind Cat's user avatar
4 votes

Why is the specific heat of conductors and insulators not same at high $T$?

The Dulong-Petit law says that at high temperatures, the molar heat capacity of a solid substance approaches $3R$, regardless of whether it is an electrical conductor or insulator. It is a ...
J. Murray's user avatar
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4 votes

On the non-quasistatic transfer of heat

Do we arrive at the same final temperature as if the same spheres had equilibrated via a quasistatic process? If so then, rigorously, why? Of course; by conservation of energy, since nothing else ...
Chemomechanics's user avatar
4 votes

Why is rock or metal often cold to the touch but wood or plastic is not?

I can confirm that the granite slab feels cooler than paper or wood, despite having a greater temperature. I experimented with the following materials: A steel handle, a granite slab, a wooden chair, ...
AlphaLife's user avatar
  • 12.5k
4 votes

Can the temperature of a steel ladle in boiling water exceed the temperature of the water?

The system is not at equilibrium, so there is energy flowing between the various parts of it (and also energy flowing into and out of the system as a whole). But thermal energy still flows only from ...
Ben's user avatar
  • 1,484
3 votes

Can a tea light really heat a greenhouse?

This is a heat transfer rate problem. The rate of heat generated by the combustion minus the rate of heat transferred through the walls to the outside environment. The bigger this number, the warmer ...
Ian's user avatar
  • 31
3 votes

On the non-quasistatic transfer of heat

I submit to you that the way you have phrased the question is actually ill-defined. You have tacitly assumed two pieces of matter whose interaction is strictly thermal energy exchange without any ...
hyportnex's user avatar
  • 19.7k
3 votes

Heat Transfer between 2 bodies

Since you don't mention any type of thermal contact resistance, I'm going to ignore that aspect and assume that the contact is thermally perfect. As @Gert notes, the bodies must be initially separated ...
Chemomechanics's user avatar
3 votes

Heat transfer vs. Volume transfer

Imagine running the water at a very low flow rate, so low that the heated water reaches ambient temperature by the time it comes out of the tap. In this scenario, water coming out of the tap will ...
Puk's user avatar
  • 13.8k
3 votes

Can people feel the low heat radiation from very cold surfaces?

While I have not done the numbers for your very particular follow up question (nevermind that it's impossible to reach 0K), I have every reason to believe the person will survive. Consider the night ...
Cort Ammon's user avatar
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3 votes
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Heat equation two stage process - Additivity? some other approach?

Because the equation you're solving—the heat equation without power generation—is a linear homogeneous partial differential equation, you can superpose the results of boundary condition changes at ...
Chemomechanics's user avatar
2 votes

Cup of warm water suspended in a pot of water held at a steady boil

Indeed, the boiling point of water is 100°C, thus to clarify, the reason isn't that the water inside the cup is salt water. Firstly, you have to understand that extra energy is needed for water to ...
Jelly Qwerty's user avatar
2 votes

Different colors and their heat absorption capabilities

For conducting an analysis as you want you must fold the colour within the actual solar power spectrum. An accurate analysis would involve the knowledge of the actual reflectance spectra of the ...
Alchimista's user avatar
  • 1,729
2 votes

On the non-quasistatic transfer of heat

If you equilibrate the two spheres using a quasi-static path or an irreversible path, in both cases you end up with the same temperature, $(T_H+T_C)/2$. So the entropy changes of each of the two ...
Chet Miller's user avatar
  • 34.1k
2 votes
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Heat equation and discontinuous thermal conductivity in the finite volume method

Put a grid point $x_j$ at the interface between the two regions. Then $$k^+\frac{T_{j+1}-T_j}{\Delta x}=k^-\frac{T_j-T_{j-1}}{\Delta x}$$That is, the heat flux is continuous at the interface.
Chet Miller's user avatar
  • 34.1k
2 votes
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How does wetting cotton increase its UV transparency?

Cotton fibers are somewhat transparent, and much of the interaction of light with those fibers is scattering at the air/cotton interface. A wet cotton fiber has a water/cotton interface instead of air/...
Whit3rd's user avatar
  • 9,923
2 votes

Non-linear thermal conductivity for thin materials

The formula for heat conduction is also correct for thin sheets. The thin metal sheets have two functions: reflecting back thermal radiation (and thereby preventing heat loss due to another mechanism ...
Sebastian Riese's user avatar

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