Temperature Definition and 1000 Threads

Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is colder or hotter.
Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have used various reference points and thermometric substances for definition. The most common scales are the Celsius scale (formerly called centigrade, denoted as °C), the Fahrenheit scale (denoted as °F), and the Kelvin scale (denoted as K), the last of which is predominantly used for scientific purposes by conventions of the International System of Units (SI).
The lowest theoretical temperature is absolute zero, at which no more thermal energy can be extracted from a body. Experimentally, it can only be approached very closely (100 pK), but not reached, which is recognized in the third law of thermodynamics.
Temperature is important in all fields of natural science, including physics, chemistry, Earth science, astronomy, medicine, biology, ecology, material science, metallurgy, mechanical engineering and geography as well as most aspects of daily life.

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  1. Clara Chung

    Exploring Temperature and Energy: Answers to Common Questions

    1.If temperature is just a measurement of KE, can a system with higher temperature contains lower internal energy than a system with lower temperature? 2.Can energy flow from an object with higher temperature to an object with lower temperature even if the internal energy of the object with a...
  2. Claude_mar

    Predicting internal temperature with or without HVAC

    Hi, how to predict indoor temperature with or without HVAC? I have the internal temperature's value, the external temperature's value and the temperature of HVAC's air output. I want two function, one with HVAC on and other with mode off. Hp: start time 0, end time Tend. Tend has values from 0...
  3. binbagsss

    Plot Heat Capacity vs Temperature for a 2 state system microcananonical ensemble

    Homework Statement I have ##C= NK_B (\frac{\epsilon}{K_B T})^{2}e^{\frac{\epsilon}{K_B T}}\frac{1}{(e^{\frac{\epsilon}{K_BT}}+1)^2} ## and need to sketch ##C## vs. ##T## Homework Equations See above The Attempt at a Solution I have ##C= NK_B (\frac{\epsilon}{K_B...
  4. G Cooke

    I Can Temperature Changes Alter Humidity in a Completely Filled Closed System?

    We know that for a closed system, isobaric heating decreases the humidity and isothermal compression increases the humidity. But assuming that we start with the volume completely filled with humid air, is it not true that any increase in temperature must also increase the pressure? If so...
  5. A

    I Determining the total energy released by a compost pile

    The heat source for this experiment is a compost pile (1 cubic meter), I know that the inside of the pile will reach approximately 50C for 2 weeks or so. Right now it's winter so the temperature will stay around 0C (average). The thermal conductivity of compost can vary greatly but in this case...
  6. T

    What happens to wavelength as temperature of air increases?

    Homework Statement what happens to wavelength if temperature increases? Homework Equations V= lambda * frequency The Attempt at a Solution I'm guessing since no change to frequency is stated?.. and I know that the speed of sound increases as temperature increase. The wavelength would have to...
  7. A

    I Determining the energy released by a flame

    I've found a lot about using water to find the amount of heat released by something but the experiment I want to run would take about two weeks to complete so that's probably not a viable solution for me. I know what the temperature will be and that it will remain mostly constant, is there...
  8. gonadas91

    High temperature Superconductors: Cuprates

    Hi everyone, I am about to finish my PhD and need to start thinking about trying to move somewhere else. One line of research that caughts my attention is that of the cuprates, and the study of their phase diagram. I would like to know if someone can suggest a very recent book or review article...
  9. I

    Calculating saturation and dew point given pressure and temperature

    Hi guys and gals. Hobbyist, not a student. I've had great input here in the past. Thank you in advance for any direction and help figuring this out. -Seth- 1. Homework Statement I'd like to learn how to calculate relative humidity, saturation, and dew point under differing pressures and...
  10. A

    B Temperature in the space between planets of our solar system?

    I know that the overall temperature of the universe is microwaves at 3 Kelvin or so from the Big Bang, but is this mostly for deep space? Or is this pretty much the temperature in our solar system also, assuming a coordinates some distance away from any of our planets but still within our solar...
  11. parshyaa

    How anders celcius defined temperature scale.

    What made anders celcius(founder of °c temperature scale) to use water as a bench mark for measuring temperature, why he used water's freezing point as 0°c and boiling point as 100°c, is there a reason or he just used water so that it can work easily.
  12. A

    Temperature physical or chemical change

    If you Increase or decrease temperature and change states of matter, that's a physical change. But are there any circumstances where temperature can cause a chemical change? Like if increasing temperature could break the bonds between the atoms and separate them? And I don't mean a combustion...
  13. Timmykuku

    Does Ambient Temperature Affect Cold-Blooded Animals' Size?

    Since cold-blooded animals, such as lizards, turtles, &c., take on the temperature of their environment, can we expect them to linearly and volumetrically expand/shrink in warmer/cooler environments? In addition, can we expect them to follow the simple equation: ΔV=βV0ΔT, for some volume...
  14. Saharka

    Otto cycle combustion heat question

    I have been trying to determine the efficiency of an ideal Otto cycle based on the compression ratio of my car and the heat of combustion of gasoline and I think I'm not entierly wrong but there is something quite off. When trying to calculate the temperature of the combustion stage my result...
  15. R

    Why is vaporisation rate increased by a decrease in pressure

    In my textbook, it says that the rate of vaporisation can be increased by (a) increasing the temperature or (b) reducing the pressure. I understand why an increase in temp can lead to more molecules breaking away from the liquid and entering the vapor state. More temp = more energy = more...
  16. physea

    Role of pressure and temperature in chemical reactions

    Hello! I have a feeling and I would like to know if it is true. I feel that if a reaction between two gases, takes place in high temperature only (perhaps with the presence of a catalyst), then if we increase the pressure high enough and keep the temperature low, the reaction may still take...
  17. FQVBSina_Jesse

    Heat transfer by radiation and Temperature difference

    Hello all, this is related to a project that I am working on. It is not directly related to the project but as part of it, I thought it would be a good idea to check the temperature difference that I need to maintain in order to effectively transfer a certain amount of heat between the TH in a...
  18. N

    Calculating Internal Energy & Temperature Change of Ideal Gas

    Homework Statement What is the change in internal energy (in Joules) of an ideal gas that does 4.675x10^5J of work, while 2.95x10^6J of heat is transferred into the system and 7.95x10^6J of heat is transferred from the system to the environment? Calculate the change in temperature of the two...
  19. Chadi B Ghaith

    I Find Oven Temperature at various moderate mode?

    Hello, I want to convert gas unit into oven temperature (Fahrenheit, Celsius). Which formula I can use? Also I want to know at which oven temperature we can assume it as moderately high or cool temperature??
  20. onargaroberts

    Impact of the engine thermostat temperature setting on engine efficiency

    Will a four cycle, internal combustion engine have greater thermal efficiency with a relatively cool jacket water temperature, say 160 degrees F, or a relatively hot water jacket temperature, say 190 degrees F? These specific numbers are only important in as much as they are commonly available...
  21. D

    Electromagnetic Radiation temperature

    Is there a meaningful way to convert the energy of an electromagnetic wave to a temperature? I mean this more along the lines of how the universe has a temperature of 2.7 kelvin due to electromagnetic radiation. I'm honestly just curious to determine the temperature of the universe after nearly...
  22. B

    Thermal expansion of a pipe with wall temperature gradient

    I have a pipe holding liquid at 80°C. The outside atmosphere is -2°C. The pipe gets a temperature gradient over the wall thickness. The outside fibers will thus restrain the inner fibers from expanding. I would like to know the increase in the inner dia of the pipe. I have found temperature...
  23. A

    I Unruh effect, temperature and particle density....

    Hi all, This is a followup to a question I asked a number of years ago about the Unruh effect. I understand that an accelerated observer will see warm gas of particles following a blackbody distribution with some temperature T, where as an inertial observer would see none. My question is: how...
  24. P

    Temperature as a function of vibration energy quanta

    Homework Statement Consider a small cluster of four copper atoms. Assume, that each atom can oscillate around its equilibrium position independently of the other atoms. Let us model each direction of vibration as a harmonic oscillator, whose energy is quantized Evib = ¯hω(n +1/2), where ω =...
  25. Edward258

    Find the temperature increase of a rotating disk

    Homework Statement It's a Blackbody radiation problem: A beam of wavelength λ, in the state of right circular polarization, leads to an absorbent disk.The mass of the disk is m, it's specific heat is C, and its moment of inertia is I .The disk is initially at rest, but after a lapse of time...
  26. Kara386

    I Why does LED band gap decrease as temperature increases?

    I've tried to summarise the explanation my professor gave. Is it correct or have I misunderstood? It's a highly simplified view of things anyway, but here goes: Taking the simplest 1D case, there are two possibiities for an electron in the lattice: it may be scattered and move back the way it...
  27. ShayanJ

    A Near horizon limit and Hawking Temperature of the horizon

    One way that people introduce the Hawking temperature of an event horizon, is by taking the near-horizon limit of the BH metric and then do a Wick rotation of the time coordinate. Then, the regularity of the metric requires that the Euclidean time to be periodic. But how can this give us the...
  28. N

    Final temperature after pouring soda into glass with ice....

    Homework Statement Soda from a ms=12 oz can at temperature Ts=13 degrees C is poured in its entirety into a glass containing a mass mI=0.16kg amount of ice at temperature TI=-19.5 degrees C. Assume that ice and water have the following specfic heats c1=2090 J/(kg*C) and cs= 4186 J/(kg*C), and...
  29. H

    How to determine temperature of filament?

    I was wondering in class today how I could determine the temperature of a filament in an incandescent light bulb? Mainly then so I could determine the thermal energy outputted through radiation. So after school I used a test circuit. I started with the Stefan-Boltzmann law which is Q =...
  30. G

    Finding Average Temperature Using Boltzman Constant

    Homework Statement Deep in space, there is a particle density, p, is 1.01cm^-3. Pressure is extremely low, P, is 5.1 x 10^-17 N/m^2. What is the average temperature of mostly empty space? Answer in K Homework Equations T=P/pKb The Attempt at a Solution I plugged in...
  31. Monsterboy

    To find final temperature when an evacuated bottle is opened

    Homework Statement The internal energy of air is given, at ordinary temperatures, by ## u= u_o + 0.718t ## where ##u## is in kJ/kg, ##u_o## is any arbitrary value of ##u## at 0oC, kJ/kg, and t is temperature in oC. Also for air, ##pv= 0.287(t+273)## where p is in kPa and ##v## is in m3/kg...
  32. Akmalidin

    Battery temperature while charging

    Hello, I am made a powerbank myself with li ion battery. I used boost converter and everything is fine, charging my phone. But the li ion battery and my boost converter is getting really hot while charging my phone.The battery capacity is 4400mah. I don't know the reason for such temperature...
  33. Kaneki123

    Effect of Temperature on Solubility

    Solubility of some some solids decrease with increase in temperature...There is an exothermic reaction so a lot of heat is produced in the solution...My question is that why does solubility decrease?...Any increase in temperature (the heat we provide) should just excite the molecules more and...
  34. Selveste

    Temperature dependent heat-conductivity

    Homework Statement A cylinder has length L , inner diameter R_1 and outer diameter R_2 . The temperature on the inner cylinder surface is T_1 and on the outer cylinder surface T_2 . There is no temperature variation along the cylinders lenght-axis. Assume that the heat conductivity k...
  35. A

    Could a good conductor be heated past the temperature of....

    Could a good conductor, like some metal, be heated past the temperature of the heat that's heating it. Like if I use a 100 degree flame and hold it for hours on some piece of metal, could the metal go above 100 degrees? And I'm not talking about special cases. I mean does this generally happen?
  36. Galbi

    Water evaporation by negative pressure and 0% of RH

    Greetings! I'm trying to evaporate water in some samples. I'm trying 3 methods. Baking samples with 100°C, normal air pressure, and normal RH. Put the samples in 0% RH, 23°C, and normal air pressure. Put the samples in container of -15 psi air pressure, 23°C, and normal RH. The total amounts...
  37. W

    Statistical definition of temperature

    hello everyone. i need help understanding this statement: d(lnΩ)/dE = 1/kbT so Ω are the posible microstates for energy E, and the derivative of Ω w.r.t E is 1/kbT. why? what i understand so far is: looking at the division of energy of two "connected" systems the energy will divide itself in a...
  38. M

    Temperature of Plexiglass due to laser strike

    Hello, Any hep is appreciated. In the lab we want to use a 0.3mm sheet of plexi to reduce the intensity of the UV KrF laser. We want to determine the temperature of the plexi sheet after the laser beam strikes it. We have all the information about the laser... Is there a specific formula...
  39. J

    How to calculate time to change the temperature of metal

    So I'm looking to calculate the time required to raise the temperature of a piece of lead. What I know so far: Mass of metal: 4 grams Initial temperature: 250 degrees Celsius Final temperature: 350 degrees Celsius Specific heat of lead: 0.13 kj/kg I'm very new to thermodynamics and don't know if...
  40. F

    Temperature of two bodies in the same room and under the Sun

    Hello Forum There are three different mechanisms to transfer thermal energy: conduction, convection and radiation. It is well known that when two objects having different temperatures T1 and T2 are in contact, they will eventually reach a common intermediate temperature (the weighted average...
  41. M

    I Calculating LED Efficiency with Radiant Power and Temperature

    i wonder if it is possible to get the efficiency of an LED just by knowing the radiant power an the outside temperatur. i also know the temperatur of the emmited light. well they say the LED has an efficiency >1 because it takes heat from the out side and turns it into rays. so these two things...
  42. A

    Thermodynamics/ Heat,volume and temperature

    Homework Statement The formation of ice from water is accompanied by: A. absorption of energy as heat B. temperature increase C. decrease in volume D. an evolution of heat E. temperature decrease For the first one I think it's correct but I don't know the explanation For second one it...
  43. I

    Temperature inside a box as particles escape a small hole

    Homework Statement Edit: Thanks to gneill for showing me the LaTeX ropes. Equations should work now. A perfect gas enclosed within a container escapes into vacuum through a small circular hole. The particle flux through the hole is ##\frac{nc}{4}## and the energy per particle escaping can be...
  44. Riverbirdy

    Solving for temperature and volume of Dietrici Equation

    Hi, guys! I came across hard stuff today. I really hope you can help a poor little worm like me. How do you solve for v & T correspondingly for equation like this⇒p = [RT/(v-b)]e^(a/vRT)? What's the technique? How do you call it?
  45. A

    Does heat from drilling cause damage to drill bits?

    if i heat up my drill bit before drilling, will that result in less coefficient of friction between the drill bit and wood material or metal material? and if so yes will it give me more time before the drill bit wears out because of high temperature as it will be harder to reach high temperature...
  46. victorhugo

    Air friction and speed & temperature

    1. It makes sense that air drag increases with speed, but is it a direct increase or to the square of the velocity? (so the faster you go the more energy wasted?) 2. What is the relationship between air temperature, pressure, and air drag? I can see how on a warmer day the molecules are further...
  47. G

    Calculate the Flame temperature

    Homework Statement A fuel gas consists of 75% butane (C4H10), 10% propane (C3H8) and 15% butene (C4H8) by volume. It is to be fed to the combustion chamber in 10% excess air at 25°C, where it is completely burnt to carbon dioxide and water. The flue gases produced are to be used to generate 5...
  48. sliperyfrog

    Ideal gas law, Find the Temperature of the container?

    Homework Statement [/B] There is a lid on a .25m diameter, .30m tall cylindrical container enclosing .021kg of air. The lid is held in place solely by atmospheric pressure. It take 220N of force to pull of the lid at an atmospheric pressure of 101kPa. What is the Temperature of the enclosed...
  49. A

    What is solidus and liquidus temperature of granite?

    My understanding is that because a rock is composed of variety of minerals, so it does not have fix melting point, rather there is a range below which whole rock is solid and above which whole rock is liquid. I want to know this liquidus and solidus temperature for granite rock based on pressure...
  50. arpon

    Temperature dependence of Cv at very large volume

    Homework Statement In the case of a gas obeying the equation of state $$\begin{align}\frac{Pv}{RT}&=1+\frac{B}{v}\end{align} $$ where ##B## is a function of ##T## only, show that, $$\begin{align}c_v&=-\frac{RT}{v}\frac{d^2}{dT^2} (BT)+\left(c_v\right)_0\end{align}$$ where ##\left(c_v\right)_0##...
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