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 and frequency relationship in case of closed end standing waves

I am trying to predict temperature based on the resonant frequency in Closed-End Air columns. I am using this formula: $$\tag{1} T = \frac{16 \times (f^2) \times L^2}{(2n -1)^2 \times \Gamma\times R} ...
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Why is entropy in a heat flow process always positive?

Entropy in a quasistatic heat flow process is given by $$\Delta S=C_1\ln(\frac{T_f}{T_{10}})+C_2\ln(\frac{T_f}{T_{20}})$$ Where $C_1, C_2$ are heat capacities at constant volume, $T_{10}<T_{20}$, ...
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How water anomalies affects the Mpemba effect?

I understand basic explanation of Mpemba effect like this: Distant molecules are easier to realign into new formations. But if we compared two bottles of water like in Mpemba effect and one of them ...
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Can super heated air be used to drive a turbine driven engine? [on hold]

Air a mixture of gases is ever trying to expand. By accelerating this property can air be used as a fuel in a turbine driven engine which can give sufficient output to be used in an automobile.
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+50

How can it be that the beginning universe had a high temperature and a low entropy at the same time?

The Big Bang theory assumes that our universe started from a very/infinitely dense and extremely/infinitely hot state. But on the other side, it is often claimed that our universe must have been ...
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Fall in temperature due to expansion

The following lines are from my book. The gas is heated and allowed to expand at such a rate that the fall in temperature due to expansion is less than the rise in temperature due to the heat ...
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27 views

An interesting question on the mass of a droplet of liquid experiencing the Leidenfrost Effect

Background and Inspiration: I have seen numerous demonstrations of the leidenfrost effect, both on the internet and in my mother's kitchen. But I started wondering about a general case after having a ...
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How does a heated constant volume flow behave, for an expanding flow tube leading into the free atmosphere

I have a helium gas flow with a flow rate that has been set to a constant value ($0.3\,m^3/h$). It's streaming upwards in the picture, and beyond the upper big red dot position, it meets the ...
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Why the breath sometimes warm and sometimes cold? (2 different explanations!)

If you blow air against your hand with your mouth open, you feel warm breath. If you do with with your lips closed except for a small opening, you feel cold breath. One explanation from here says ...
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Why is my breath hot when i open my mouth all the way, but cold if I blow like a whistle? [duplicate]

I observed this as when I want to cool my soup I blow like a whistle and when I want to warm my hands I open my mouth more as my breath is warmer now.
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Is the gas constant really a constant?

For ideal gases we have $$ C_p-C_v=R $$ now the left hand side of this equation is temperature dependent, so how is it possible that gas constant $R$ is temperature independent?
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Are black holes hot?

If no light can escape black holes, in my mind they would act as a greenhouse, collecting radiation from the stars or CMB or anything. Or is all this energy just absorbed by the black hole?
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1answer
40 views

Is the size of the universe directly related to its temperature? [duplicate]

The universe was at its hottest when it was at its smallest. As the universe expands, it gets cooler. Is the expansion of the universe the direct cause the cooling? I suppose it would be more clear ...
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46 views

How does one calculate the applied magnetic strength of a superconductor?

How does one calculate the applied magnetic strength of a superconductor? I spoke with a faculty member about this question. He explained to me that if one can break the spin pairing of two electrons ...
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1answer
14 views

Cooling effect of sipping

Is the primary action of cooling of a sipped hot fluid explained by the reduced flow of the hot fluid, the air cooling of the fluid as it is sipped or another factor?
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83 views

What does a hot, optically thin gas *look* like?

In another question I tried to answer what a sample of the Sun's photosphere or core would look like, if it could be brought into the lab. Here is a broader question - if I have a small inert ...
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2answers
363 views

Temperature in a Voltaic Cell

The potential difference across a voltaic cell varies with temperature. But my question is whether the voltage increases or decreases as temperature rises. According to the Nernst equation, the two ...
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1answer
490 views

How effectively does heat flow through copper wire?

If I have a line of copper wire (lets say 1 meter long, 1mm thick) and one end is a flattened disk of copper about the size of a quarter, and I apply a lot of heat to it (I'm talking 800 Celsius) will ...
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604 views

Does extreme cold make **everything** extremely brittle?

First of all, I'm genuinely sorry if this question isn't "serious" enough for this forum! A common cliche in movies and tv is that a very tough object (eg the villain) is frozen, and then hit with ...
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68 views

How can I estimate the cooking time of a roast?

I never remember what worked before, or to write it down someplace. In any case the size and starting temperature will vary. The instructions I learned from refuse to give a time at all, and the ...
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1answer
2k views

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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3answers
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Why does increasing the temperature of a thermistor decrease it's resistance?

Surely, upon an increase in temperature, the atoms within the thermistor would vibrate with more energy and therefore more vigorously, hence making the electrons flowing through the electric circuit ...
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Why does heat added to a system at a lower temperature cause higher entropy increase?

Entropy is defined in my book as $\Delta\ S = \frac{Q}{T}$. To derive the formula it says that entropy should be directly proportional to the heat energy as with more energy the particles would be ...
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31 views

Why does hot air rise?

Why does hot air rise? I did an experiment: I made a model of hot air and cool air with marshmallows and toothpicks. The hot air had more volume than the cold air. Then, I weighed it. They both ...
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Given temp and conductivity can I back-calculate to resistance, in order to plug in a new temp value and calculate a more accurate conductivity?

Background: I used a small CTD (conductivity, temperature, depth) recorder to log a series of dive profiles in a mixed coastal estuary. The recorder logged observed temperature and conductivity every ...
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What are the Fermi and Debye temperature constants?

What are the Fermi temperature and Debye temperature constants? We were discussing these in class and I don't fully understand what these constants are or why we have them. Can anyone explain?
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109 views

Heat Equation with In-Depth Radiation Exact Solution

I am looking to solve the heat conduction equation in a semi-infinite solid with in-depth radiation on the domain $-\infty < x < 0$. The governing equation of this problem is: $$\rho c ...
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How to calculate the evaporative cooling rate needed to protect a house from forest fire

Recently in our area there has been a large forest fire and I've been looking into home defense from such things. I am not a physicist - but can do some basic math. I was wondering how I could ...
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1answer
128 views

How hot is your photon?

This question comes from my answer to the question Can a cubic meter of space at absolute zero have any object with mass inside? and the related discussion under it. To summarize, I stated that the ...
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317 views

Can a cubic meter of space at absolute zero have any object with mass inside?

I ask this question because, I have seen many places where they say the average temperature of the universe is some 2 degrees K and this somehow relates to mass present within a given volume of space. ...
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absolute minimum vs absolute maximum [duplicate]

there is such a thing as a absolute minimum temperature defined by At the physically impossible-to-reach temperature of zero kelvin, or minus 459.67 degrees Fahrenheit (minus 273.15 degrees ...
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1answer
96 views

What causes a heat generating source to stabilize at a certain temperature? (Answered by myself, I think)

For example, we out a heat sink on a microprocessor to keep it cooler. I understand that if we run 100 watts of electricity through the microprocessor, it will generate 100 watts of heat, or 100 ...
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526 views

Existence of negative temperatures and the definition of entropy

How negative temperatures can be possible has been treated on StackExchange before (several times in fact), but in light of some recent academic discussion, most of these answers seem to be possibly ...
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3answers
108 views

Is my conceptual understanding pertaining to heat & temperature correct?

From what I've understood: Heat is the total sum of kinetic energy translational energy possessed by individual atoms in an object. Temperature is the average kinetic energy translational energy ...
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1answer
29 views

How to calculate precipitation chance with basic weather data?

I would like to know if there is any algorithm which allows us to calulate precipation chance with following data: temperature, humidity, illuminance (in lux) and pressure. I've searched it in google, ...
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1answer
66 views

What is the overall rate of heat conduction through two pipes of different dimensions if the thermal conductivity is not constant?

I am trying to work out how I would find the rate of heat transfer through two pipes made of the same material that are joined at their ends but which have different cross-sectional areas and lengths. ...
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1answer
36 views

Why does a thermal memory need a thermal bath?

In the article "Thermal Memory: A Storage of Phononic Information Phys. Rev. Lett. 101, 267203 – Published 29 December 2008" it's said that a thermal memory need a thermal bath, similar to a power ...
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Trying to determine transient response of air conditioned room

I have an air conditioned room which intakes airflow at temperature $T_{in}$ at a mass flow rate $\dot m$. The air leaks out of the room at mass flow rate $\dot m$ and temperature $T_{room}$. The room ...
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3answers
89 views

Determining a temperature increase from heat energy [closed]

A 15.0g bullet traveling horizontally at 865 $\frac{m}{s}$ passes through at a tank containing $13.5$kg of water and emerges with a speed of $534\frac{m}{s}$. What is the maximum temperature ...
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Time required for water to freeze

recently I was wondering if there is any specific formula in order to calculate how long it takes for certain liquids to freeze (especially water). I know this depends on: the volume of the liquid, ...
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209 views

What is planetary surface temperature given constant sub-surface temperature?

If a planet of radius $R_1$ has a constant sub-surface temperature $T_0$ at $R_0<R_1$, what is the long-term equilibrium surface temperature $T_1$? Say we assume constant thermal diffusivity of ...
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79 views

How does the entropy change during the cooling of a hot coffee in a cold cup?

The second Law of Thermodynamics states that entropy always increases in the universe: things become more disorganised. This means, that if I have a hot coffee in a cold cup, then the heat will ...
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30 views

Constant volume gas thermometer

Well, in the notes I took in thermodynamics' class I have a graph that plots Pressure of boiling point $P_b$ over Pressure of freezing point $P_f$ at constant volume in terms of Pressure of boiling ...
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1answer
72 views

Increase in Solubility of a Gas with an Increase in Temperature

On the UC Davis ChemWiki I read, "some gases have an increase in solubility with an increase in temperature." I understand why this is applicable to solids in liquids such as water, but why is it ...
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1answer
52 views

How does heating in the atmosphere look above 100 km

I have tried without luck to find a graph of temperature change through the atmosphere that goes further up than about 100 km. On this graph: (Source: ...
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1answer
45 views

Thermometric Properties

A thermocouple thermometer with 10 ohms of resistance is calibrated with its hot junction and cold junction immersed in steam and melting ice respectively. An EMF of 5.6mv is measured. This ...
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1answer
44 views

Linearity of thermal expansion of metals?

I am having to do a path length correction for a metal tube (stainless steel 316, 16ppm/C) from 0-100 degC. I need to correct to within approximately 1 ppm. How much do typical engineering metals ...
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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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92 views

Why don't the collisions of the particles in a gas affect its temperature?

Temperature is defined as the mean kinetic energy of the system. Now the particles are constantly colliding with each other; as a result of which kinetic energy of each particle changes. ...
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PCF based temperature sensor [closed]

how to calculate relationship of refractive index And temperature for liquids in optics and what are the methods?