Questions tagged [thermal-conduction]
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Why does a lot of water vapour come suddenly after the heat source of boiling water is removed? [duplicate]
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 ...
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Why don't you get burned by the wood benches in a sauna?
When you go to the sauna you may sit in a room with 90°C+. If it is a "commercial" sauna it will be on for the whole day. How does it come that when you sit on the wood you don't get burned?
I ...
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Why does cold metal seem colder than cold air?
(I apologize for this elementary question. I don't know much about physics.)
Let's say that I put a metal pot in the refrigerator for several hours.
At this point, I guess, the pot and the air (in ...
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Does anything in an incandescent bulb actually reach its color temperature (say 2700 K)?
This question is inspired by a question about oven lightbulbs over on the DIY stack. It spawned a lengthy comment discussion about whether an incandescent lightbulb with a color temperature of 2500 K ...
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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°...
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Why are steel thermal mugs much better than plastic ones?
I have several thermal mugs, two of them by the same brand, have the same look, shape and size except that one is in steel (inside and outside) and the other one, plastic. Both have an insulating ...
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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 ...
user235329
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Why do we need insulation material between two walls?
Consider a slab made of two walls separated by air. Why do we need insulation material between the two walls. Air thermal conductivity is lower than most thermal conductivities of insulating material ...
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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.
Which physical ...
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Does an empty refrigerator require more power to stay cold than a full one?
Given that everything else is equal (model of fridge, temperature settings, external temperature, altitude), over a given duration of having the door closed, does it require more electricity to cool ...
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Are specific heat and thermal conductivity related?
Are there any logical relationship between specific heat capacity and thermal conductivity ?
I was wondering about this when I was reading an article on whether to choose cast iron or aluminium ...
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Why does holding a hot object with a cloth make it feel less hot?
Let's say that I held a hot object with a warm cloth. It instantly feels less hot and only warm to the touch. This is because the cloth is an insulator and doesn't allow as large a heat transfer as if ...
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How does fire heat air?
I understand that fire heats its surroundings via conduction, convection and radiation. I've read that conduction is nearly irrelevant to this process as air is a poor heat conductor. In descriptions ...
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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 ...
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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 ...
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Why does water feel cooler than air?
My first assumption was based on "evaporation causes cooling" but I realized that it is not the case as it is cooler even if I am submerged under it. Are all liquids generally cooler than air ?
Just ...
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Which would melt faster on the sidewalk, equal volumes of snow or ice?
Whilst walking back from class, I noticed the piled snow on the sides of the street still hadn't melted after a week despite it being sunny and generally warm $(15°C-18°C)$. "If that snow was ice, ...
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Why is the ground warm during winter and vice-versa?
I was just looking at the geothermal house heating in Iceland, and came to know that in the winter the water is warm, hence cools the house, but how is it hot, not about us feeling it.. My question is ...
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Cooling down a container in outer space
If I have two containers filled with very hot water(~210°F) with one in outer space and one on earth, which one has a higher rate of cooling initially? Imagine the containers are single wall metal ...
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LED Thermal Modeling (How to solve heat equation with constant heat source)
I have a mechanical design with LEDs that generate heat. I want to estimate the temperature at the LED junction vs. time, but especially at steady state.
Knowing the LED voltage drop and current, I ...
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Does Cosmic Background radiation transmit heat?
The Cosmic Background Radiation can be considered as the after-glow of the Big Bang, but does it transmit heat to objects in space? It is thermal radiation and is basically charged photons ...
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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 ...
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Can a tea light really heat a greenhouse?
It is a common suggestion amongst greenhouse enthusiasts that a long-burning tea light inside an upturned terracotta pot can be enough to keep frost away from plants. Is this possible?
Instinctively, ...
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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 ...
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Phonons and heat conduction
What is the physical picture of heat conduction in a poor conductor? In particular, I'm curious about the role of phonons in conduction in poor conductors. I know that phonons (within the harmonic ...
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What causes contact resistance?
When two components are combined in an electric circuit, there is apart from their own resistances a contact resistance at their junction. This causes a sudden voltage drop of $V_{drop}=R_{contact}I$....
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Why haven't we found thermal superconductors?
First of all I want to apologize if this is a stupid question. I'm a layman who's merely very interested in physics, without a degree to my name.
I was trying to research electric superconductors ...
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How does the sun's surface conduct thermal energy from the convective zone to the corona?
How does the surface of the photosphere conduct thermal energy from the convective zone to the corona, while remaining at such a relatively low temperature itself?
It seems odd to me that the ...
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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 ...
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What happens when you heat vodka in a microwave?
Since ethanol has a lower dielectric constant than water would the water heat up and boil before the ethanol? Would the water transfer heat to the ethanol and, since ethanol has a lower boiling point, ...
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How does hot air rise?
If a balloon is filled with hot air, it is rising due to buoyancy: the mass of the hot air inside the balloon is lower than the mass of the same volume of the cold air outside the balloon cavity.
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How much heating does Earth inner core provide to the surface?
Compared to the energy that the Earth's surface receives from the Sun, how much power comes from the inner melted core?
How important is this contribution to the surface temperature?
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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 ...
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When should I take wine out of the fridge - transient heat transfer problem
I am hosting a dinner tonight for which I'll be serving white wine (Riesling to be more specific). Generally white wine is best served chilled (not COLD!) at around ...
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Why is a sleeping bag so cold when you first get in?
I sometimes put a sweater on when I first get up on a cold morning. The sweater isn't so cold against my skin, but the zipper is. I get this. Even though they are both at the same temperature, the ...
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Cup of warm water suspended in a pot of water held at a steady boil
The question asked by a website is as such (possibly behind a paywall):
A cup of warm water is suspended in a large pot of water held at a steady boil. Will the water in the cup ever boil? Assume ...
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Why the heat flux vector at a point must be perpendicular to the temperature isothermal surface? Is it a definition or a deduction?
Before the question: I am working on numerical calculation of three dimension parabolic equation that based on Fourier's Law of which I am a little confused.
Here comes the law in modern mathematics ...
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What exactly heats a pool of water on a sunny day
On a sunny day an outdoor swimming pool will heat up fairly quickly. My question is, what is the exact mechanism for this and can we put numerical figures on it?
Given that water is clear and ...
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Is the thermal conductivity of metals affected by magnetic fields?
Especially for a ferromagnet a magnetic field should have a field-induced band shift in the density of states but I wonder if this shift is big enough to be significant and affect the thermal ...
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Are two thin blankets significantly warmer than a single thick blanket?
Almost every source I can find online maintains that two 0.5 cm blankets are significantly warmer than a single 1cm blanket due to air trapped between the thin blankets.
However, the thermal ...
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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
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Does the order in which I layer blankets matter? [closed]
It’s getting cold where I live and I sleep with multiple blankets. I am wondering whether it generally matters how I might use blankets to keep something warm; if I put blanket $A$ on top of blanket $...
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Of all the electrical energy used in a home, is there any portion that won't eventually become thermal energy in the home?
Considering all of the appliances that the average home uses--microwaves, light bulbs, dishwashers, refrigerators--is it safe to say that all of the electrical energy in a home will be converted to ...
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Physics of heat flow or should I wear a sweater inside or insulate my walls?
This is a theoretical question about heat flow…just phrased in terms of everyday life. On first approximation, in terms of home heat loss, which makes a bigger difference or are they equivalent:
a) ...
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What's the best strategy to fully fill the fridge with beer bottles and have them all cooled?
I'm having a party.
Suppose I'd like to have a fridge full of cold ($6~^\circ\text{C}$ or below) beer bottles, in as short a time frame as possible. The fridge indicates that it is targeting (and ...
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Why does an ice stupa not melt for 6 months?
https://www.youtube.com/watch?v=-1s0K_MKAgI&t=303s
In this video at 3:55, Mr. Wangchuck explains that the ice stupa doesn't melt because it has less surface area for a given volume compared to ...
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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 ...
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Improving our homemade hot tub design? [closed]
My brother and I built a wood burning, convection based, thermal circulating hot-tub. (With and oxyacetylene torch, lots of 1.5" pipe, a brake drum, and a thirty year old jacuzzi). Our design is ...
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Does adding cold water to evaporative air coolers actually produce colder air?
Or should it be the other way around, because hotter water evaporates easier than cold water?
I know this sounds stupid, so just hear me out.
I use an evaporative cooler and add normal room ...
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