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. 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...
  2. 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?
  3. 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...
  4. 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)
  5. 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...
  6. 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.
  7. 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?
  8. 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...
  9. D

    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...
  10. 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...
  11. R

    Calculate the Temperature and Pressure of a melting point

    Adiabatic increase in pressure implies Tds=0, can someone tell me how to proceed?
  12. 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}...
  13. 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...
  14. 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} ## ##...
  15. 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...
  16. 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...
  17. 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...
  18. 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...
  19. 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
  20. 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...
  21. 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...
  22. tanaygupta2000

    Statistical Mechanics: Two systems reaching an equilibrium temperature

    First I found partition functions of both the systems and hence total energies of them using above formulas. Z(A) = (1 - e-ε/kT)-1 and Z(B) = (1 + e-ε/kT) Then I equated these values to the given values of total energies. I got: For System A, T(A) = ε/kln(2) > 0 For System B, T(B) =...
  23. WateryFungi

    Engineering Thermodynamics - Control Volumes find final temperature

    Hi I'd like to know if my current approach to the problem has any issues. My attempt: Balancing the equation: Qin + Win +mΘout = Qout + Wout + mΘout Qin+m(hin + v2in/2 + gzin) = m(hout + v2out/2 + gzout) Wflow + ΔU + m(hin) = m(hout) I factored out the mass: wflow + Δu + hin = hout And I used...
  24. Graeme M

    What does "surface temperature" mean?

    I have been reading about the "greenhouse effect" of Earth's atmosphere, having been conscious that while I generally understand it I had never really examined it more closely. A problem that bothers me is mention of "surface temperature" which seems to vary according to context. In some...
  25. H

    What's the normal low-load working temperature for an SMPS transformer?

    Hi! I have question about high frequency transformers inside switch mode power supplies (SMPS). Is it normal for them to become hot under no load or low load? For example if power supply is rated for 144A at 13.8V and I only pull from it 2A at 9.6V, it normal that transformer becomes about 50C...
  26. sneakycooky

    The relationship b/w infrared, temperature, and electron excitation

    Homework Statement:: 1. Does the increase in kinetic energy in (for example) water that results from increasing its temperature result from electron excitation (i.e. increasing electron energy levels) or simply increasing their velocity or vibration amplitude/frequency? 2. If excitation is...
  27. Harini Krishna

    Food temperature question -- eating cold meals

    Hi, Can i know how having cold meals daily effects out health in long term? Thank you
  28. C

    Temperature variations in body regions

    In thermal scanners in airports, subway, hospital and other stations to monitor the Coronavirus carriers. They point it at the foreheads, or is it the neck? We use home fever thermometers on our ears or armpits and not forehead. What are the variations of temperature in different parts of the...
  29. J

    Heat transfer through a MultiLayer Cylinder (find the Temperature inside)

    Hello, I am a Mechanical Engineer a little out of practice on Heat transfer. I am trying to solve this problem. It must be solvable but i have yet to find right equations online. I have a multi Layer Cylinder made up of C350 marraging Steel,Zinc Alloy-12 , then 6061 Aluminum T6. All that is...
  30. patric44

    A question about the specific heat and Debye temperature

    this is my attempt of a solution , but my only equation is should i convert Θ to Celsius , and if i did the specific heat of the other substance is greater , how is that if its inversely proportional with temperature ! . and the other Θ is 200 K so it should be less ?!
  31. G

    Below what freezing temperature is it not possible to have frost?

    I once had a job servicing microwave repeater station. About 1000 ft up on the tower are reflectors/antenna they have heaters that came on at 40 degrees F. Heaters stayed on until about minus 18 degrees F then heaters turned off. When it gets cold enough all humidity in the air freezes then...
  32. V

    Temperature of the tank in a superheater

    how can i find the rate of change of temperature of the tank for a superheater? Or is there any relationship between the change in temperature of the tank when it is filled with hot gas?
  33. ib43

    Thermal physics problem -- Pressure and temperature of air in a refrigerator

    There is this one problem from past exam papers which I cannot seem to do: The air in a kitchen has pressure 1.0 x 10^5 Pa and temperature 22'C. A refrigerator of internal volume 0.36 m^3 is installed in the kitchen. (a) With the door open the air in the refrigerator is initially at the same...
  34. B

    Temperature inside an enclosed space

    its summer where i live and the ceiling space gets extremely hot, much hotter than ambient outdoor. under a shade outdoor, the air temp beneath shade will be colder than air temp in sunlight. yet in a space with no air flow, the temp is always hotter from my experience. why is this? this isn't...
  35. Z

    Threshold voltage shift vs temperature

    In a field effect transistor, does the threshold voltage decrease with increasing temperature? Imagine that there would be an increase in thermally generated carriers and thus the device would reach saturation faster? I realize the mobility would decrease, but the increase of thermal carriers...
  36. Y

    Temperature change in a gas expansion

    1- ##\delta P_V =(\frac{\partial P}{\partial T} )_V \delta T_V## 2-##\delta V =(\frac{\partial V}{\partial T})_P \delta T+(\frac{\partial V}{\partial P})_T \delta P## so ##C_v \delta T=-P\delta V=-P((\frac{\partial V}{\partial T})_P \delta T+(\frac{\partial V}{\partial P})_T \delta P)## I can...
  37. M

    Marimba bar tuning and temperature

    Hi all. I make marimbas - www.marimbaaustralia.com - have a look. I also invent new versions for schools. I DO NOT KNOW algebra almost at all, so go easy on me please! I try to tune to exact Fundamental note frequency (and the first overtone as well, if possible). I also try to tune when it is...
  38. Y

    Low-Temp Liquid Helium System: Evaporation Heat & Temperature

    We consider a system composed of liquid helium in equilibrium with its vapor at very low temperature T, each phase being considered extensive. We neglect the mass of the gas compared to that of the liquid, as well as the heat capacities of the gas and the walls compared to that of the liquid...
  39. M

    Optimizing Marimba Tuning for Temperature Variations: A Scientific Approach

    I make marimbas, and I have invented a few variations (www.marimbaaustralia.com) I am interested in how sound moves through the wooden bars - in particular the effect that temperature has and how to compensate during tuning on different temperature days. I have almost no algebraic knowledge...
  40. NP04

    Converting Between Temperature Scales: Finding the Relationship Between M and F

    M F Ice Point 77°M 32°F Steam Point 437°M 212°F 437°M - 77°M = 360°M 212°F - 32°F = 180°F ∴ M = 2F M = 2(68°) M = 136° But this is incorrect. The answer is actually 149°M. Please help.
  41. Rahulx084

    Thermodynamics -- Temperature of a Heat Source?

    In heat engine we define a heat source from where heat is transferred to the system, we say that heat source has a temperature ##T_h## , When we define a Carnot heat engine, the first process we have is an isothermal expansion and we say heat has to come in system through this process and here...
  42. W

    Abaqus FEA - how to choose temperature for the sky on a clear night

    Hi, I want to model the phenomena that a windshield gets covered in ice during a night with clear sky even tough the air holds a temperature of a few degrees above zero Celsius (at which water freezes for sea level pressure). Clearly the windshield gets a temperature below zero Celsius, and...
  43. B

    Is a Rate of 100K/s an Intuitively Offensive Way to Measure Temperature Change?

    Question: This would be the right approach to do this problem? Thanks!
  44. Sabra_a

    Engineering Smoke interface height and temperature

  45. J

    Stirling engine LTD (Low Temperature Differential) plate size / energy

    i need a simple calculation of a stirling ltd surface area calculation per watt produced and would a very rough surface and very large surface area hinder heat flow if the distance to re generator is extreme /would folding the surface area of a flat plat ltr help increase the power of engine...
  46. Z

    I Mobility and resistivity as a function of temperature

    Referencing: http://www.vlsiinterviewquestions.org/2012/07/21/inverted-temperature-dependence/ Mobility decreases in a MOSFET with increasing temperature However, referencing: https://www.quora.com/Why-does-resistivity-of-semiconductors-decrease-with-increase-in-temperature Resistivity...
  47. maistral

    Boundary conditions for convective heat and mass transfer + wall Temperature

    I am operating via finite differences. Say for example, I have this pipe that contains a fluid. I have the boundary condition at x = x1: k is the effective thermal conductivity of the fluid, T is the temperature of the fluid at any point x, hw is the wall heat transfer coefficient, and Tw is...
  48. C

    Thermodynamics - Change in temperature for heated slabs of steel

    Just started this topic so I'm not sure if this is the correct way to solve this, any help would be appreciated. mass of object x change in temp x specific heat capacity= heat change in temp= heat/(mass of object x specific heat capacity) Mass= 700kg Specific heat capacity of steel= 0.42kJ/kgC...
  49. S

    Water temperature with two materials cooling it

    I converted dm3 to m3, all the degrees to kelvins and found out the specific heat constants of iron and aluminium (0,45 and 0,91 KJ/kg K), but now i am failing to understand how this was supposed to be calculated. The equation given doesn't really help, as there are two unknowns in it: Q and the...
  50. karush

    MHB 3.1.5 AP Calculus Exam average temperature

    309 average temperature $$\begin{array}{|c|c|c|c|c|c|c|} \hline t\,(minutes)&0&4&9&15&20\\ \hline W(t)\,(degrees Farrenheit)&55.0&57.1&61.8&67.9&71.0\\ \hline \end{array}$$ The temperature of water in a tub at time t is modeled by a strictly increasing, twice-differentiable function W. where...
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