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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Why does an optical pyrometer read low in the open?

An optical pyrometer relies on the fact that the brightness of heat radiation from a body depends on its temperature. I have come across the fact that an optical pyrometer invariably reads low when ...
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10 views

Reactor opening and total time to reach a specific temperature

Let's say I have a reactor (we assume that its shape can be approximated by a horizontal cylinder) in which there is air at the temperature of 1000K and at pressure of 1.5 bar. Now, I want to open it ...
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55 views

Expansion in bimetallic strip

Suppose there is a bimetallic strip with thickness 't' .The coefficient of linear expansion on heating the metals are alpha 1 and alpha 2.Now if the bimetallic strip is subjected to a temperature ...
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3answers
39 views

Hot Chocolate- cooling itself down

If a hot cup of hot chocolate is just standing there, can it cool itself down by transferring the kinetic/thermal energy that the liquid has into the mug/cup?
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1answer
22 views

Why are negative temperature coefficient thermistors accurate for measurements of low temperatures?

Why are negative temperature coefficient thermistors accurate for measurements of low temperatures? How does higher resistance at low temperature accurately measure the temperature?
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1answer
57 views

Estimate post-shock temperature of nuclear explosion

I was recently shown a very interesting sequence of images depicting the expansion of the fireball of Trinity explosion, a nuclear weapon's test conducted in New Mexico in 1945. I read here that ...
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8answers
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Celsius to Fahrenheit confusion: why there is no 1 to x ratio?

Why is it not possible to know the ratio of 1°C to how many Fahrenheit and use that to convert from or to Celsius/Fahrenheit? What is really happening? Fahrenheit increases linearly and so does ...
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1answer
27 views

Compute affect of a shower on density altitude

As a pilot I have a basic understanding of density altitude, how temperature affects the effective air pressure: I noticed recently that I have difficulty breathing when I take a shower in Santa ...
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1answer
74 views

Maximum Temperature?

I have been reading a lot about wavelengths of light and Planck's law and such. Curious as to whether a minimum wavelength of $h$ (Planck's Constant) indicates that there is in some way an absolute ...
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67 views

Upper bound for the Kelvin scale [duplicate]

Possible Duplicate: Why is there no absolute maximum temperature? On the Kelvin scale, absolute zero represents the temperature at which there is no thermal motion. Consequently, speaking ...
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58 views

First law of thermodynamics with additional term

I read in a paper that a "known expression for the heat received by a body" is $$dQ=dU+pdV-\mathbf{v}\cdot d\mathbf{P}$$ where $\mathbf{P}$ is the linear momentum of the body, $p$ is the pressure, ...
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1answer
60 views

How to calculate max temperature craft needs to withstand near the Sun

The Solar Probe Plus fact-sheet states that the craft will approach to the distance of 9 solar radii to the surface of the Sun (Approx 6.26e6 km) and its heat shields must withstand 1644K of heat. I ...
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1answer
51 views

Managing nuclear waste [closed]

Suppose you are trying to dispose of used uranium fuel rods. Once they are cooled and contained in zirconium pods, how would one try and send those pods to the earths core? This is all hypothetical. ...
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39 views

Infrared light and heat

I know that mid wave IR, long wave IR, and far IR are all infrared light that we feel as heat. Often, even when it is cold and windy, if I face the sun in a sunny spot it feels like it is 80 degrees F ...
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1answer
356 views

If I mix 1 unit of water at at 30C° with 1 unit of water at 60C°, is the resulting water at 45C°? [closed]

I'm curious how temperatures work when mixing water. I'm not very good at physics but I'm always learning. Let's say I've 1 gallon of water at 30C° and 1 gallon of water at 60C°, and I mix them ...
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3answers
66 views
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5answers
2k views

0 Kelvin body moving

As many books say: Temperature is (proportional, almost, etc...) average kinetic energy of particles. My question is this. "Suppose there is a body somewhere in empty space which moves at ...
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3answers
218 views

A physical explanation for negative kelvin temperatures

Just to get the thoughts rolling... Consider a two state system with discrete energy levels $E_1$ and $E_2$ where $E_2 > E_1$ which contains $N$ particles. We can easily deduce that the state of ...
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1answer
1k views

Why does a water drop on a hot plate at 150°C evaporate faster than on a plate at 200°C?

I recently read that: A drop of water landing on a hot plate at 150°C (300°F) evaporates in a few seconds. A drop of water landing on a hot plate at 200°C (400°F) survives a whole minute. How ...
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2answers
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How hot can plasma get?

I remember reading about an experiment where fine rods of tungsten were super-heated with millions of amps of electricity, melting them into ionised gas and were then compressed (by magnetic fields?) ...
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unit conversion issue

I have the following equation where $ T_0(x) $ measures the temperature in Celsius at point x. The parameter values are as follows. My question is how to handle the second term $Q_m \over ...
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1answer
39 views

Equilibrium temperature of closed system

Body X of temperature 0° C is brought into thermal contact with body Y of temperature 100° C. X has specific heat capacity higher than of Y. The masses of X and Y are equal. By my reasoning, the ...
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1answer
58 views

Temperature of system in canonical ensemble

Upon reading Reif's explanations relating to systems exchanging energy and the canonical ensemble (Reif, Fundamentals of statistical and thermal physics, p. 95ff and p. 202ff), I am led to conclude ...
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1answer
209 views

Is there any metal or any material that can survive the Sun? [closed]

If we were to send a unmanned spaceship through the Sun. What material can survive?
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1answer
120 views

Methane under pressure [closed]

A tank is filled with liquid methane. Then it is closed. It sits in an infinite room at STP (standard temperature and pressure). (Initial temperature is not important; assume density of liquid ...
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1answer
73 views

Time to decrease water temperature by 5F from different initial temperatures

Is the time to (naturally) decrease temperature of water by 5 degrees the same, regardless of the initial temperature? Imagine 3 glasses of water (a, b c) in a room temperature of 70F. There are 3 ...
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1answer
93 views

Electrons and photons at absolute zero?

I know that molecules can't move at absolute zero (hypothetically of course). But what happens to electrons and photons?
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1answer
32 views

Resistance including temperature - tungsten

I am doing a paper on calculating temperatures of tungsten filament inside a halogen lamp. I have measured different voltage-current levels and calculated the resistance. Then, I have used formula ...
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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 ...
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8answers
159 views

Visualising gas temperature and gas pressure

Gas pressure is created when gas molecules collide with the wall of the container creating a force. Gas temperature is a measure of how fast the molecules are moving / vibrating. However, they both ...
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2answers
829 views

Why isn't the Earth's core temperature the average of its surface temperatures?

Assuming that the earth is spherical, that its temperature is continuous, and that some other more or less realistic conditions hold, we might think that the Earth's core temperature should be about ...
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38 views

Thermal AdS3 in Chern Simons

I am currently working with (2+1) gravity in Chern-Simons formulation and I have a question about thermal AdS. The way I understand that one retrieves thermal AdS is by Wick rotation and ...
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3answers
107 views

Can a single particle be “heated” by radiation?

From the point of view of statistical thermodynamics, a single particle doesn't have a phase (state of matter), nor temperature. What would happen if heat is transported to this single particle via ...
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1answer
196 views

What is the significance of the Debye temperature from a materials perspctive?

If I look at a table of different metals and their Debye temperatures, what does the variation in these temperatures tell me about these materials?
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2answers
198 views

Temperature of a falling meteor

I am reading "What if?" article https://what-if.xkcd.com/20/ and I'm interested in it's scientific background. Mr. Munroe writes: As it [the meteor] falls, it compresses the air in front of it. ...
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Is temperature a Lorentz invariant in relativity?

If an observer starts moving at relativistic speeds will he observe the temperature of objects to change as compared to their rest temperatures? Suppose the rest temperature measured is $T$ and the ...
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2answers
131 views

Why don't objects radiate off all of their heat energy?

Imagine a solid box in deep space. Solids are as far as I know constructed by positive nuclei in some sort of coherent structure, with electrons orbiting nearby too. Both the nuclei and the ...
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2answers
111 views

Would an ideal gas be colder at higher altitude due to gravity?

Since gas molecules are affected by gravity, wouldn't that make gas molecules at higher than average elevation slower (at the top of their ballistic parabola) and thus colder than air molecules ...
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1answer
41 views

why there is no temperature and density in the formula of the electrical resistance?

Why there is no temperature and density in the formula of the electrical resistance? We all know, that the electrical resistance depends on length, temperature, density( material). Why is the ...
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2answers
142 views

Why does heat added to a system cause an increase in entropy that is independent of the amount of particles in the system?

Say we have two gas containers of $N_{2}$ at the same temperature of $300 ~\text{K}$, one containing $10^{23}$ particles and the other containing $10^{13}$ particles. If we add a quantity of heat to ...
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1answer
84 views

How does a photon raise the temperature of a gas?

The temperature of a fixed volume of a gas is increased when it interacts with radiation. Why does the temperature increase (i.e. why does the velocity of a gas molecule increase) when a photon is ...
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48 views
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69 views

temperature from a molecular point of view

The electric fan increases the velocity and hence the kinetic energy of the molecules in the air. this would mean that the temperature has increased. What's wrong with a conclusion? I want you to ...
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78 views

Mercury-in-glass thermometer

Question from my textbook: Jason says 'The mercury in the thermometer can be replaced by coloured water. The thermometer will function well after recalibrating using a similar method to calibrating a ...
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26 views

How long does it take for space dust to stop irradiating energy?

I heard that space dust is detectable because it irradiates on the infrared part of the spectrum? Does this happen forever? Won't it stop after some millions of years? Does it have to irradiate until ...
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1answer
165 views

What is the temperature of the event horizon?

In a discussion with my son about absolute zero, we arrived at the conclusion that the event horizon might be the place to look, as it "absorbs?" all energy, including light. Found this in the ...
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1answer
63 views

What is the difference between temperature difference and temperature change?

In a course of mathematical modelling that I am taking, there is a great confusion between the concepts of temperature change due to a unit heat input at some position $x$ and time $t$, and the ...
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6answers
12k views

Why can't a gas be liquified by pressure above its critical temperature?

What is the cause behind a gas being difficult to liquify above its critical temperature no matter how much pressure is applied on it?
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1answer
48 views

sudden volume increase piston

I am wondering what happens in the following situation. I have a piston filled with an ideal gas for which I suddenly/instantaneaouly iscrease the volume. In particular I want to know what happens to ...
2
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4answers
486 views

Why does my house seem to warm faster in summer than it cools in winter? [closed]

In summers when we switch off the air conditioner, the room seems to instantly get hot again. But in winter, when we switch off the heater the room seems to remain hot for some time. Why this ...