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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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help: calculating surface temp for rotating planet from solar constant 1366 w/m2

I'm interested in calculating the maximum surface temperature for a rotating planet from the solar constant. I can calculate the solar constant for a planet at any distance from the sun, no problem, ...
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Why 2nd-order derivatives of $G$ are discontinuous in 2nd-order phase transition?

In most undergraduate books, it is said that for second order phase transition Gibbs free energy and its first order derivatives are continuous at transition temperature. But the second order ...
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Entropy and temperature of small systems

I've been struggling for a while now in understanding the concept of entropy as a function of the internal energy. Textbooks typically call $g(E)$ the number of microstates compatible with an energy $...
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Is the surface temperature of the sun constant?

I was just wondering that during the suns mains sequence would it maintain a constant temperature at the surface and only cool once the hydrogen in its core runs out, or is it always slowly decreasing?...
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Negative surface gravity and temperature

Is it possible to have negative surface gravity $\kappa$? Also, since $T=\frac{\kappa}{2\pi}$ then if you have a negative surface gravity then that implies negative temperature too right?
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Need to find Specific Heat [closed]

An unknown substance of mass 4.5 kg has absorbed 3000 J of heat energy to raise its temperature from 25°C to 27°C. Find the Specific Heat. The two equations we use in class for heat are Q=mc∆T and Q=...
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Why is the thermodynamic definition of temperature only valid for large systems?

I remember my thermal physics instructor telling me that the definition of temperature, $$\frac{1}{T} \equiv \left(\frac{\partial S}{\partial U}\right)_{N, V},$$ is only valid for (sufficiently) large ...
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Exact mode of evaporation

I am having a doubt regarding what is the exact mechanism of cooling during evaporation. At one place it is said that as surface water molecules evaporate it takes heat from surroundings and hence ...
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Why are higher frequencies amplified less by filling a bottle with warmer water instead of colder water?

Out of curiosity I was trying to figure out what makes the sound of hot water versus cold water filling a bottle different, but I'm unable to find any explanation as to why such differences occur. ...
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In two connected rooms, each heated or cooled, which temp will prevail? [closed]

Two connected rooms of the same volume that are fully and perfectly insulated, each having a closable and perfectly sealed and insulated vent and a hatch between the rooms also perfectly sealed and ...
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Why does quantum mechanics become unnecessary at sufficiently high temperatures?

In my statistical mechanics intro class, we are taught that at sufficiently high temperatures, the quantum treatment of things becomes unnecessary. Why is this? Can this be shown using certain ...
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Calculating the temperature of flowing gas in copper tube

A copper coil is immersed in a water bath. The water bath provides heat to heat the nitrogen gas when it passes through the copper coil. Nitrogen gas at room temperature is passed through the copper ...
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(Color Temperature) How to calculate combined color temperature (kelvin) of two different sources

I have been looking for a while but I can't seem to find any information on this. I would like to figure out the formula to calculate the CCT of two calibrated sources of light relative to their ...
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Condensed water freezes and other water condenses around it

So I was on a plane and tiny crystals of ice formed on the window glass. This window is formed by a few screens of glass (maybe or maybe not) with vacuum inside. I think the frost was due to some ...
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Does a gas canister change temperature as gas is released?

If you have a deodorant can, it is obvious that the gas leaving the can has cooled as it expands. However, is there also a change of temperature of the gas that remains within the canister? My ...
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Why is finite temperature many-body perturbation theory computed in the grand canonical ensemble?

Why does virtually every textbook and paper treat many-body perturbation theory at finite temperature in the grand canonical ensemble? Is it not possible to formulate a canonical theory where all ...
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Temperature of an annealed palladium wire in air

I'd like to estimate the temperature of a palladium wire that undergoes annealing by electric current in air. A simplified scheme is shown here: My first guess was to apply the Joule-Lenz formula: $...
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cellphone heat generation

Cellphones = 1 billion phones (1,000,000,000) Environment = 1 billion KiloLiters water (1,000,000,000,000 Liters) Power = microwave radiation @ 1 watt/phone antenna Time period = 1 year / 365 days / ...
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Confusion on Centigrade/Celsius Scale

There came the centigrade scale. The issue was that many solid/liquid thermometric substances didn't respond to temperature linearly so different thermometers produced different results. This was ...
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Adiabatic flame temperature of ethanol in high pressure environment

I'm building a rocket engine and need to know the temperature of the gases inside the combustion chamber (ie the stagnation temperature). The combustion chamber pressure is 5 atmospheres. The ...
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Does the temperature of a rapidly moving macroscopic object higher than its stationary state? [duplicate]

I learned that the average kinetic energy has $$ E_k = \frac{3}{2}\ kT. $$ But if heat is in essence molecular motion, then is a rapidly moving ball different with a still one?
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How can temperature be defined as it is if entropy isn't a function of energy?

I've been taught that for large systems, the temperature of a system is defined as $$\frac{1}{T} \equiv \left(\frac{\partial S}{\partial U}\right)_{N, V}.$$ I have a problem with this definition, ...
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How to prove Caratheodory's Concept of temperature

Lenker T D . Caratheodory's concept of temperature[J]. Synthese, 1979 This is a discussion in the article: let $S_i$ be the state space of the thermodynamic system $\sum i = 1, 2, 3$, and assume ...
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Vortex tube without compressed air

I am looking for an apparatus to cool/heat air without moving parts and using only a pressure source. From this, I came to a "vortex tube". However, all practical implementations are based on ...
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How to calculate total heat energy with fluctuating temperatures?

I had a question relating to a math problem that I'm doing. Let's say I have a heater that produces heat until it reaches a specific temperature, after which it turns off until it reaches a minimum ...
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How is the relationship of the value $kT$ and a degree of freedom derived?

Sources that discuss the derivation of the Maxwell-Boltzmann Statistics end up with two unknown constants ($\alpha$ and $\beta$) through the Lagrange Multipliers, of which $\alpha$ is derived by ...
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Absence of phase transitions in quantum 1D systems at positive temperature

While it is generally said that there are no phase transitions in classical lattice systems in one spatial dimension, there are also exceptions to this rule. Rigorous proofs involve some fairly strong ...
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Entropy derivation question

I’m using Atkins thermodynamics book and he has a section I don’t quite understand. The line I’m particuarly question is the one befor (5.2) where he says “by Kelvins formulation of the second law”. I’...
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How to achieve a desired relative humidity in a sealed environment

I need to find out how much water to add (in milliliters) to a sealed test tube (which has a volume of 53 milliliters) to achieve a relative humidity of 60% when the temperature is heated 80 degrees ...
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Proof of the Direction of Heat Flow

I’m reading Callen's thermodynamics book and he proves that heat tends to flow from a system with a high temperature to a system with a low temperature by assuming the temperature difference of two ...
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Replace warm air with cold air

In summers i.e. now, my room has hot uncomfortable air in night,but outside air is cold 4-5 degrees Celsius colder than inside, my room has windows parallel to wind flow, so though wind flows in night ...
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Why does entropy of an ideal gas break the third law of thermodynamics? [duplicate]

I was recently looking at the entropy equation for an ideal gas, show below $$S=NR\left\{\frac{5}{2}+\ln\left[\frac{V}{N}\left(\frac{2\pi mRT}{h^2}\right)^{3/2}\right]\right\}$$ And what troubles me ...
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Meaning of zero temperature in terms of $1/T=\partial S/\partial E$

Suppose we have a $NVE$ system of a pure crystal. From the definition of the temperature in macroscopic thermodynamics, $$\frac{1}{T}=\left. \frac{\partial S}{\partial E}\right |_{V,N}$$ . Then ...
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Where in microwave ovens things warm faster?

I want my mug to boil as soon as possible and I prefer not to throw energy away. Where in microwave ovens things warm faster?
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Why is the Sun approximated as a black body at ~ 5800 K?

Apparently spectral solar radiation is approximated by a black body at 5800 K. The spectral black body distribution (Planck distribution) is shown below (from Incropera, Fundamentals of Heat and Mass ...
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Could someone explain what it means that temperature is a lagrange multiplier of energy? [duplicate]

I have looked online but I couldn't find anything that explains this definition
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Luminosity of a white dwarf

I have a very simple question, yet i am confused.Can someone tell me why in an H-R diagram the white dwarfs are at the bottom left? As in I understand that they would have a high temperature when they ...
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Why does a cooking thermometer show different temperatures when touching the container of a liquid?

I have a cooking thermometer that looks like a 10-15 cm long metal rod, that can be inserted into the thing you want to measure the temperature of: When inserted into boiling water, I observed that ...
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Black hole absorbing photons?

If a black hole has a radius that is not that much smaller than the wavelength of light emitted by the sun, and is at the same temperature, shouldn't it be able to absorb photons as well as emit them? ...
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Temperature as function of $CO_2$

The carbon stored in fossil fuels must have been taken out of the earth atmosphere from CO2 in past periods by plants. Thereby reducing the amount of CO2 drastically and increasing the amount of O2 to ...
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Why does the temperature have to change when there's no heat loss in an adiabatic expansion?

Adiabatic expansion is known to cool gases to a substantial temperature and it's caused by pressure drop. Now if I have a tank full of an ideal gas (nitrogen) at high pressure and temperature, and I ...
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Dependence of a pendulum's period on temperature

Does the time period of pendulum just increases with temperature or proportionately with temperature. If former is correct why latter is incorrect
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How many $\text{watt}$ are required to obtain $500°$$\text{C}$? [closed]

I am using two $1000$ $\text{watt}$ heating elements in a cylindrical chamber of volume $7500$ $\text{cm}^3$ with a limited opening at two sides. The cylinder has a radius of $6$ $\text{inch}$. How ...
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Temperature Less Than Nothing? [duplicate]

How temperature can be less than nothing or less than absolute zero?And how atoms interact in this level?
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A place with no temperature?

We all know that a place with no fluid is called vacuum, how can we describe a place with no temperature?, is right to say "no temperature" ? And if not why can't we say IT?
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Thermodynamics - best fan speed to heat a room (for the same heating power)

Let's assume we have a cold empty room (with no person in it, therefore - barely little air movement) and we want to heat it up. In the room, we have a hot-air blower that has two fan speed-settings, ...
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What is the reason for the emission of electromagnetic waves from the sun? [duplicate]

What is the reason for the emission of electromagnetic waves from the sun and why curve its in about the visible light is maximum?
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Manual jack up of Maxwell-Boltzmann scale parameter?

I first noticed this phenomenon when i was a child, about 4 decades ago. I needed a piece of wire but could not find a pair of pliers with which to cut the wire. So i used a technique i once saw my ...
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How much change in Earth's orbital distance to change average temperature by 1°C?

How much closer/farther would the Earth need to be to/from the Sun to effect a $1 \sideset{^{\circ}}{}{\mathrm{C}}$ increase/decrease in average temperature?
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Change of specific internal energy due to temperature and volume

The change of internal energy due to temperature and volume may be written as $$ dU=C_V dT + \left( T\left(\frac{\partial S}{\partial V}\right)_T-P\right) dV$$ where $$\left(\frac{\partial S}{\partial ...