# Questions tagged [temperature]

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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### Temperature of a resting glass of water

It’s summer and summers have become more and more hot&humid lately. This got me curious about the dew point and then wet bulb temperatures, both for scientific and (maybe, someday in the future) ...
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### $i\epsilon$ prescription for finite systems [closed]

What is physical interpretation of path integral for finite time and finite epsilon (i.e without taking limits time->+-inf, epsilon->0)? Does it mean you are doing some finite temperature qft ...
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### The usage of temperature in quantum mechanics

This is a follow up question for my previous question, because now I am more confused than I was before. In a regular quantum mechanics course, temperature plays no role as it does not appear in the ...
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### Does color temperature limit how much a laser of a given wavelength can heat a target?

The Sun has a peak wavelength of around 500 nm and an effective surface temperature of 5770 K, and sunlight cannot be focused to make something hotter than the Sun, because this would be heat flowing ...
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### Calculating temperature change out of a room [closed]

Currently I'm trying to find how the outside temperature affects the internal temperature of a room through its walls. I'm trying to use the convection heat transfer equation to find the exterior wall ...
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### Can particles feel hot to the touch? [closed]

The other day, I got a tiny splash of hot cooking oil on my hand. But I could barely feel it because it was so small. That made me wonder: how hot would a small collection of atoms need to be for me ...
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### Why does the temperature-volume diagram look the way it does?

Suppose we have a piston-cylinder system containing compressed water (water that is not about to vaporize). The pressure of water is equal to the sum of atmospheric pressure and the pressure exerted ...
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### Two interacting blackbodies (one inside another) - when will thermal equilibrium be attained? [closed]

As I understand it, an ideal blackbody absorbs (and subsequently starts emitting) all incoming radiation. In typical setups like determining a planet's temperature given its albedo and distance from a ...
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### Precise relation between temperature change and physical quantities [duplicate]

I've learnt that many physical quantities like length or volume etc depend on the change in temperature and some proportionality constant as: $\Delta{L}=l\alpha\Delta{\theta}$. In our physics class, ...
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### How does the temperature of the condenser impact an air conditioner's energy usage?

Air conditioners have a condenser after the compressor, in the high pressure side of the system. I've found graphs that show the compressor takes less energy if the condenser is colder. That makes ...
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### Proportionality of Pressure and Temperature in defining Absolute Temperature scale

I am studying thermodynamics and came across this kind of loop: First, an absolute temperature scale is attempted to be defined as follows Assume that temperature is proportional to the pressure of ...
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### Why the Sun has a higher temperature than humans?

Why the Sun has a higher temperature than humans if the energy/gramme of matter ratio of humans is greater than that of the Sun?
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### Feasibility of entropy at zero temperature

I remember a college lecturer of mine once gave me this equation of entropy during one of his lectures on thermodynamics: \begin{align*} \Delta{S} = \frac{ d {Q} }{T} \\ \end{align*} I found out ...
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### Does Pipe Temperature Directly Correlate To Water Temperature? [closed]

I need to know if just by taking a boiler flow pipe temperature that will tell me the water temperature that is flowing through the pipe. For example if the water from the boiler travelling through ...
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### Can metal get hotter than heat source? [closed]

Trying to understand something I have actually witnessed.. My cousin is a welder, and claims that a 400 degree acetylene flame will in time melt steel. He showed me a 400 degree flame, then had a ...
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### At what size of matter does the second law of thermodynamics breakdown?

I'm in high school and I was studying some topics related to heat transfer. While studying, I was curious about why heat strictly flowed from a higher temperature (more energy) to a lower temperature (...
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### Where do we get $\Delta U = nC_vT$ from? [duplicate]

The change in internal energy at constant volume is $Q=nC_v\Delta T$ Why does the same equation apply for constant pressure?
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### Role of the natural temperature scale in the anomalous dimension of the renormalization group

In David Tong's lecture notes on statistical field theory, the concept of anomalous dimensions is introduced by considering the scaling of the correlation function \langle \phi(\mathbf{x}) \phi(\...
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### If I'm inside water, is the amount of heat energy I can receive capped because water can't go above 100°C?

I just learned about double-boiling, where instead of putting a pot directly on the flame stove (where it can get too hot), you put a big tub of water on the flame, and put the pot in the tub of water....
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### What do we mean when we say the CMB has a temperature and how do we measure it?

I have read this: An object without any internal degrees of freedom, like a single photon, can't really have a temperature. But an ensemble of photons can have a temperature. If you put an ensemble ...
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### Temperature as a frequency

In Arnold's Mathematical Methods of Classical Mechanics, he leaves as an exercise to show that if $S(E)$ is the area enclosed by a closed phase curve of energy $E$, then $T:=S'(E)$ is the period of a ...
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### Should I hold a baby formula bottle to cool it down faster?

This is an interesting and somewhat surprising physics problem - holding a hot object in your hand will cool it down faster, even if the air around is colder. I guess that 90% of people would be ...
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### How can photons be absorbed by matter, without causing ionization or new photons?

Let's say we have a gas, of argon atoms for example. We raise the temperature of the gas to 20,000K. Some atoms collide with enough energy that the atoms ionize, into free electrons and ions. So, now ...
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### Variation of fan air temperature with angle

On a very hot summer's day, I was on my porch using an electric fan and I noticed that the air it blew had different temperatures. As you move away from the center and towards the outer border, I ...
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### In a universe with no photons, will everything necessarily be at absolute zero temperature?

Imagine a universe governed by the same physical laws as ours, i.e., the same fundamental forces, with the only caveat that there are no photons, hence no electromagnetic radiation in this universe. ...
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### Why can't we see green color in the sky? [duplicate]

From sunrise to sunset we can see a variety of colors in the sky. For example, during morning the most dominant color is blue whereas during sunset orange,red,yellow and there shades are more dominant....
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### How can a free electron and an ion in a plasma recombine without violating conservation of energy and momentum?

This question is the inverse of How does ionization of gas molecule affect the translational kinetic energy of the molecule? The answer to that question is that a molecule cannot spontaneously ionize: ...
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### Modified Joule-Thomson expansion

I was trying to solve a thermodynamics problem about the Joule-Thomson (Joule-Kelvin) expansion and I can't reach the answer. The book has the solution, but there's a term which I don't get where it ...
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### Mass-volume relation for a star - explanation

In the game Universe Sandbox, I created a gas giant (made of pure hydrogen) and begun increasing its mass and watched how its radius changed and how it evolved into a star. While it was already a ...
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### How does ionization of gas molecule affect the translational kinetic energy of the molecule?

Some things I understand to be true: When we raise the temperature of a gas to around 10-20,000 Kelvin, the molecules of gas start to ionize, form a plasma, according to the Saha equation. The ...
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### Why is warming food in the microwave work and not heat? [duplicate]

In Schroeder's An Introduction to Thermal Physics, heat is defined as the "spontaneous flow of energy from one object to another" and work is defined thermodynamically as any other transfer ...
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### Heat equation two stage process - Additivity? some other approach?

I'm struggling a bit how to apply a standard solution to the heat equation to my own practical problem. I have some intuition, but do not know whether this intuition is justified. I don't understand ...
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### What causes the latent heat of solidification?

Every explanation that I read says: "When a crystal (solid state) forms from a liquid, heat is being produced." This seems rather weird, why would the production of something as ordered as ...
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### Why clothes keep us warm?

I want to understand why clothes keep us warm. I understand that they reflect back thermal radiation and also trap air thus significantly reducing cooling due to thermal convection. My question is, do ...
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### Average kinetic energy variation between molecules in liquid [closed]

Suppose I have an insulated container filled with a liquid such as water with a known average temperature, pressure, and volume such as 300 degrees Kelvin, the average pressure at sea level, and a ...
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### Relationship between density and temperature - How to know the precise temperature at which a bell inside a Galileo Thermometer will sink?

A Galileo Thermometer consists of bells placed inside a tube that's filled with liquid. As the temperature increases, the fluid density decreases. This leads to a decrease in the buoyant force, and ...
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### Earthen Pots made in summers vs winters

I've heard my parents saying that the water in earthen pots that are made in winters cools more than a pots that are made in summers. Is this true according to physics? I understand the process of ...
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### Rotating a Pot of Boiling Water on a Stove

I have just boiled a half dozen eggs and wanted to ask about a phenomenon I have witnessed for years but have bottled up inside for so long. Why, when the water is near boiling and nice and hot, does ...
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### When we pour cold water on a closed jar containing only hot water and water vapour, why does the hot water in jar start boiling?

Here is a video link for the experiment. In the experiment, cold water is being poured on a closed jar containing hot water and water vapour and we observe that the hot water inside jar starts boiling....
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### What's the meaning of 'cold' in the CDM model?

On Wikipedia, it says In cosmology and physics, cold dark matter (CDM) is a hypothetical type of dark matter. According to the current standard model of cosmology, Lambda-CDM model, approximately 27% ...
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### Why does a heated body emit a continuous spectrum of waves, while a burning body emits one color?

Why does a heated body emit a continuous spectrum of waves (as I understand it, that's why they burn red/white/blue), and a burning body is one color? as I understood it, for example, the green flame ...
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