What is Temperature: Definition and 1000 Discussions

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. patric44

    Temperature Distribution of Current Carrying Wire in Matlab

    hi guys i was trying to solve this non linear ode using the shooting algorithm in Matlab : i am not sure how to solve it using the normal shooting algorithm i have , since no other boundary at x = L/2 was given to check the shooting ?! function dTdx = bar_temp(x,y) k = 72; h = 2000; epsilon =...
  2. J

    Ideal gas law problem -- Pneumatic piston movement with air temperature changes

    I have come up with the change in height as 170 cm. My professor does not want to solve for the problem for a reason I do not understand. 170 cm is not part of the answer key. The answer according to the answer key is 65 cm. My attempt is: Initial temperature: p=F/A; (50 *9.8) / (pi * 0.05^2)...
  3. A

    Equilibrium temperature in a homogeneous section (stationary regime)

    I believe it is just an arithmetic medium, but I am not sure. Could someone explain to me?
  4. Astronuc

    DOE ARPA-E, ULTIMATE—Ultrahigh Temperature Materials Program

    WASHINGTON, D.C. – The U.S. Department of Energy today announced $16 million in funding for 17 projects as part of Phase 1 of the Advanced Research Projects Agency-Energy’s (ARPA-E) Ultrahigh Temperature Impervious Materials Advancing Turbine Efficiency (ULTIMATE) program. ULTIMATE teams will...
  5. Kathhhriine

    Thermal physics -- Converting the internal energy of argon atoms to temperature

    I tried using U=3/2 NKbT, but i don't seem to get the correct answer..
  6. Narayanan KR

    Magnetic Permeability: Temperature Effects

    One more thing i forgot to add, is magnetic permeability of a metal constant irrespective of its temperature including superconducting temperature ?
  7. N

    I What happens to the temperature of a superconductor?

    Consider the following setup: Stationary magnet and Superconductor are fixed and Moving magnet is allowed to move freely in the horizontal direction. Assume the superconductor as Type I superconductor. Following figure shows the Horizontal Force acting on Moving Magnet vs Distance curve...
  8. Q

    Normal Stress in Rods Experiencing Temperature Changes

    Now here is the part where I'm sort of stumped myself: Could someone let me know if my reasoning is valid? The professor explained it during office hours and all I got out of that was that something cancels out and the answer is 0.
  9. N

    Temperature of a Solar panel in space

    Consider two 1 square meter marble slabs each of mass 1 kg floating in space facing the sun such that light from the sun incident perpendicularly on the flat faces. At equilibrium, power received from the sun 'PS' equals the power being lost in the form of radiation 'PR'. PS = PR (at...
  10. WMDhamnekar

    MHB Maths in Temperature and ideal gas Thermometer

    Hi, I didn't understand the maths involved in the below article in regard to temperature and ideal gas thermometer. If any member knows it, may reply me. If triple point of water is fixed at 273.16 K, and experiments show that freezing point of air-saturated water is 273.15 K at 1 atm...
  11. Athenian

    2D Steady-state Temperature in a Circular Plate - Bessel Function

    I learned about Bessel functions and steady-state temperature distributions in the past. Recently, I was searching online for some example problems on the topic and found the "original question" along with the solution online as a PDF file. While I am unsure will it be appropriate for me to...
  12. F

    Boiling & Critical Temperature: Understanding The Difference

    Are boiling temperature and critical temperature the same or they are different things?
  13. A

    EM radiation temperature vs particle temperature

    I just realized I'm having a problem in understanding this. So let's take an example the CMB is around 160 Ghz and the blackbody temperature within this frequency range is 2.7K which is rather cold as it is close to absolute zero. Then let's take another example, Iter plasma will achieve about...
  14. J

    Radiative cooling time derivation (for ambient temperature = 0 °K)

    as T_∞ = 0 , I use Q=−F\epsilon A\sigma T^4 for this problem as the integration is much easier, so we start with mcdTdt=−F\epsilon A\sigma T^4 rearrange so T is on one side and t is on the other: −mcF\epsilon A\sigma T^4dT=dt on the left side I integrate from the initial temperature (Ti)...
  15. A

    Physical state given the critical temperature and critical pressure

    Summary:: I have two substances H2O and CH3OH given at a temperature T and pressure P. I also have critical temperatures and pressures. How can I find the physical states of these substances. My teacher recommended me to use the Antoine equation and find the saturation pressure, but I can't...
  16. T

    Temperature and Sound Wave Velocity: Exploring the Proportional Relationship

    Apologies if this is a question with a basic answer, I'm coming back to physics after many years of being away from it! I read somewhere that for longitudinal sound waves traveling through air, if the temperature increases by 1 degree celsius then the velocity of the wave will increase y 0.6...
  17. B

    I want a temperature controller for a 12V, 40W ceramic cartridge heater

    Dear friends, I am in a search of a temperature controller for 12V, 40W ceramic cartridge heater! I can not change the heater because of my application. I want to purchase a simple PID temperature controller available in the market. But I am not sure whether they can provide me the 12V output...
  18. J

    I Is Nuclear fusion possible at room temperature with high preassure?

    If it is theoretically possible to compress hydrogen to core of the sun pressures at normal room temperature (practically impossible), the molecules become so close to each other that they could fuse at room temperature without the need of creating millions of degrees kelvin.
  19. P

    I Why can you not describe massive neutrinos with a temperature?

    In the Wikipedia article for CvB, it mentions the following: "The above discussion is valid for massless neutrinos, which are always relativistic. For neutrinos with a non-zero rest mass, the description in terms of a temperature is no longer appropriate after they become non-relativistic; i.e...
  20. S

    Highest theoretical temperature on Earth

    I had read somewhere that this value is 130 °F at sea level (and thus the 134 °F one at Death Valley back in 1913 is suspect). Is there some paper that explains how this figure was derived?
  21. O

    Emissivity of a very high temperature object

    I am looking for data on the total hemispherical emissivitie from a Platinum surface at high temperature 1400 - 2000 K. In this temperature range the Platnium surface will color from red, orange to white. I learned that, practically, the bove mentioned emissivity will approach to one in this...
  22. K

    Why is entropy of an object inversely related to its temperature?

    I read in a book "Quantum Space" by Jim Baggot, page 290, that the entropy of an object is inversely proportional to its temperature. (He was describing the temperature of a black hole. Does this statement only apply to black holes?) No doubt he is correct, but wouldn't an increase of energy...
  23. S

    B Understanding 3D Temperature Direction Change with 8 Corner Points

    So I have a cube in 3d space and this cube is made out of 8 coordinate points at each corner. Now I have a temperature reading at each point of these corner points. Inside the box I have another point, I want to be able to use the information from the 8 points surrounding the the one middle...
  24. cwill53

    Calculating Pressure & Density Proportions with Changing Altitude & Temperature

    I got the correct answer to this question with the following calculations, but I do need some correction in terms of what units I'm integrating across. ρ##\rho ## is density. mtot=n##m_{tot}=nM##, where n is the number of moles of a substance and M is the molar mass of the substance...
  25. il postino

    Chemistry Calculate the boiling temperature of methanol from thermodynamic data

    Calculate the boiling temperature of methanol at 60 atm knowing that Tc = 513K, Pc = 78 atm and the acentricity is 0.555. I would like you to help me start the exercise. I thought about using the Pitzer Correlation to be able to calculate the fugacity coefficient, but I don't have the...
  26. B

    Simulate the temperature inside an aquarium tank

    there's a website to size an aquarium heater or chiller. This is just for learning purposes (not for fish) but I have modified these parameters from default to perform a load calculation on a 100 gallon glass tank... For the tank temperature range I set to be between 150-160 degree F. and a...
  27. S

    Definition of temperature in weather reporting

    In my town, newspaper stories say we've had several days of record high temperatures. The stories report temperatures in the range of 107 F. However, on the same days, online weather reports show temperatures as high as 116 F. I think online weather reports use reports from amateur weather...
  28. StoningTree

    How does humidity affect air cooling?

    First i calculated the latent heat of vaporation: h_vap(15°C)= 2465.4 kJ/kg In the next step i calculated how much water is already in the air: x=0.622*j*ps/(p-j*ps)=0.00988 kg/kg where: j=50% ps=0.03171 bar p=1.01325 bar Now that i know that i can calculate the enthalpy of humid air: h_hum =...
  29. Drakkith

    I CCD Readout Noise vs Temperature

    Hey all. I tested my astro camera a while back and found what looks like a temperature dependent readout noise value. Which is odd, as everything I've ever read has told me that readout noise is independent of sensor temperature. I took 50 bias frames at 5°c intervals, from -15°c to +20°c and...
  30. Amaterasu21

    At what size is kinetic energy no longer related to temperature?

    Hi all, I've read so many times that "temperature is a measure of the average kinetic energy of the molecules in a substance," or sometimes "particles" to encompass atoms and ions too. But how big can "molecules/particles" be before their kinetic energy is no longer relevant to temperature? If...
  31. Rub3y

    At which temperature will the relative humidity in a pipeline be 10%?

    In a pipeline is an organic stream (mainly benzene and hydrocarbons, 60 m3/h) which contains 11 g/s liquid water. At which temperature will the relative humidity in the pipeline be 10 %? Is this possible to calculate? If not, which extra information would you need?
  32. J

    Understanding Vapour Pressure & Temperature Difference

    I have a problem at the very beginning. I don't know how to relate this vapour pressure to the temperature difference. I have read the hint: Recall the idea 7: for dynamical processes, at first, a mechanical equilibrium is reached, which means the equality of pressures; the other equilibria...
  33. F

    How to determine the airflow due to a change in temperature?

    (Sorry for the really basic question. Been 20 years since high school physics and I've been working in a different industry)
  34. A

    Chemical reactions to depict Le Chatelier's Principle (Temperature)

    If an endothermic reaction has a lower temperature, since the forward reaction rate decreases more, the reaction should produce more energy to compensate for the decreased energy and raise the rate of the forward reaction until it reaches equilibrium with the reverse reaction. Is this saying...
  35. Kayla Martin

    Why is the degeneracy criterion the same for all stars?

    Is it anything to do with the equation being independent of mass etc.. of the star? or to do with the Pauli exclusion principle? Any help will be much appreciated.
  36. A

    Temperature is a measure of the average kinetic energy of a gas?

    Why do they say temperature is a measure of average kinetic energy how is this possible. how can we take it is it applicable for all types of gases?
  37. mastermechanic

    Undefined log-mean temperature in heat exchanger design

    For a course project, I need to design a heat exchanger to cool electronic components in an UAV. The heat exchanger will be cross-flow air to liquid. The cold side (air side) properties are evaluated at an altitude of 7620 m and -34.5 °C. For the hot side ethylene glycol - water solution with a...
  38. docnet

    Effect of time dilation on temperature

    Thank you in advance for your replies. While reading about special relativity I started thinking about how time dilation might affect temperature. Since temperature is really the jiggling motion of molecules, does time dilation affect temperature by slowing down the jiggling motion? Or...
  39. S

    Engine working between multiple temperature baths worse than Carnot

    Let the new engine, NE, extract heat from a certain subset of these baths, and let heat obtained from the ##i^{\rm th}## bath be denoted by ##Q_i##, and let the heat rejected to the ##j^{\rm th}## be denoted by ##Q_j##. Let the engine perform an amount of work ##W##. Now right beside this...
  40. R

    Calculate the Temperature and Pressure of a melting point

    Adiabatic increase in pressure implies Tds=0, can someone tell me how to proceed?
  41. Athenian

    One-Dimensional Wave Equation & Steady-State Temperature Distribution

    To begin with, I can first let ##T(x,y) = X(x) Y(y)## to be the given solution. With this, I can then continue by writing: $$Y \frac{\partial^2 X}{\partial x^2} + X \frac{\partial^2 Y}{\partial y^2} = 0$$ $$\Longrightarrow \frac{1}{X} \frac{\partial ^2 X}{\partial x^2} + \frac{1}{Y}...
  42. I

    Question about calculating the minimum temperature in hot air balloons

    First, I tried using the Archimedes principle and calculated the weight of the surrounding air displaced when taking off. ##W = 2500\times 1.29\times 9.81 = 31637.25 N## But then, I got stuck and do not know how to proceed from here on. I don't want the full solution yet but can I get some...
  43. il postino

    Chemistry Equilibrium temperature of a water and ice system

    Equal masses of ice at –10ºC and water at 80ºC are placed in an insulated container and allowed to reach thermal equilibrium. Calculate the equilibrium temperature Data: Water(ice): 37,65 J/mol.K Agua (l): 75,29 J/mol.K ## Lf = 6011 J/mol ## I solved it this way: ## -Q_{l} = Q_{ice} ## ##...
  44. tanaygupta2000

    Problem involving Negative Temperature

    The partition function of the given system is given by, Z = 1 + e(-ε/kT) So in the '0' energy state, number of particles, n1 = [1/(1 + e(-ε/kT))]N and in the 'ε' energy state, number of particles, n2 = [e(-ε/kT)/(1 + e(-ε/kT))]N Now according to condition of population inversion, n1 < N/2 Upon...
  45. tanaygupta2000

    Temperature of Bose Einstein Condensation

    For finding n, I believe that directly applying the above formula gives the results. But I am confused whether I have to put the value of given temperature T = 100K or the actual temperature Tc for Rb-87 at which BE Condensation occurs (i.e. 100 nK, which I got from a quick Google search)? Or do...
  46. Petronius

    Thermal energy question: Final temperature of a solution

    Hello, thank you for taking the time to read this.. I hope I followed the formatting correctly and this post complies with the expectations of the forum. I solved the equation but my answer seems too low. I tried it again and arrived at the same answer. I also had doubts if it was acceptable...
  47. B

    Investigating the Impact of Heating a Substance on Room Temperature

    Through the research that I conducted is that I wasn't able to find actual supporting answer to this question. I struggle with Physics and math and because of Coronavirus my school has shut down meaning I don't have access to my teachers or tutor. The main line that i am thinking is that if it...
  48. B

    Speed of sound related to absolute temperature

    Here is the Q Very unsure about how to approach this question but this is what I have tried Any help would be really appreciated! Thanks
  49. Low-Q

    Calculating energy requirements to sustain temperature

    Hi. I have 3D printer with a heated bed, made of a 400x300 mm aluminium, that is 4mm thick. The surrounding air temperature is about 10°C. When printing with different materials, it is required to keep the bed at different temperatures. What I experience is that the driver which controlls...
  50. Hiero

    What is the true meaning of temperature? Is it global or local?

    Temperature is often imagined as a scalar field varying over (physical) space. Yet temperature seems to be generally defined as the (reciprocal) rate of change (with fixed V,N) of the entropy of a system w.r.t. the energy of that system; a seemingly global property. Is this definition only for...
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