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. porporking

    How Does Temperature Affect Electrical Resistance in Copper Wire?

    Homework Statement Hi Physicsforum, this is my first post so apology if I make unclear equation. I try to solve this question by pluging t0 as temp. at Valley and t as temp. at Antartitca directly as oppose to setting separate equation. I got different answer than the solution said While...
  2. E

    Confusion about relation of entropy with temperature.

    Why can sometimes entropy remain constant with increase of temperature and vice versa?Entropy implies transfer of heat and heat must increase with temperature.I am unable to intuitively understand.
  3. Y

    Notched specimen under constant K and temperature gradient

    Hello all, It seems like a fairly straightforward question but I cannot find any information in the literature. Let's suppose we apply a crack driving force K1=45 MPa.m^0.5 to a notched specimen with an upper shelf fracture toughness K_mat = 50 MPa.m^0.5 at room temperature T0=20 oC. Under a...
  4. D

    High Temperature, Non-conductive Material

    Does anyone know of any material that's not as brittle as ceramic that can withstand high temperatures and is non-conductive? I'm talking abou a max temp of 800degC of heat radiating from a hot steel coil. Components will be inside of the coil for a short period of time but trying to prepare...
  5. Marcin H

    Semiconductors - Drift/Mobility & Temperature

    Homework Statement Homework Equations The Attempt at a Solution I am having problems with all parts of this problem, but I'll start with part A. Comparing the 2 equations I see that Ca could be 3/2 based off the hint, but I am not sure why or how it would be 3/2 or -3/2. The problem...
  6. T

    A Planck 2015 CMB temperature individual pixel variance

    Hi, I'm hoping someone can point me in the right direction please. I'm using the Planck 2015 CMB temperature (intensity) SMICA pipeline maps (Nside = 2048) and am trying to determine the temperature variance of each individual pixel. Variance and hit-count were provided with the 2013 CMB maps...
  7. E

    Why is internal energy not a function of pressure?

    I'm reading a book on thermal physics and the author says this: "In general, the internal energy will be a function of temperature and volume, so that we can write U =U(T,V) " How do we know this intuitively and how do we know that internal energy is not a function of pressure as well?
  8. J

    Trying to Find the Type of Chart I'm Looking At

    The attached Image is a for some kind of heat map of temperature with the y-axis corresponding to the time of day and the x-axis corresponding to the time of year. It was generated in Excel from weather data files. What is this type of data representation called? I've seen the same type of...
  9. B

    Volume, pressure and final temperature

    Homework Statement a) A mass of 0.12 kg of air has an initial temperature of 500°C and pressure 0.8 MPa. If the air is expanded according to the law pV1.2 = c to a final volume of 90 litres, determine i) its initial volume, ii) its final pressure, iii) its final temperature...
  10. YNesterov

    How to find m1 in T = ( m1c1T1 + m2c2T2 ) / ( m1c1 + m2c2 )

    Homework Statement How to find mass of one of the two liquids being mixed if we know all other variables in this formula T = ( m1c1T1 + m2c2T2 ) / ( m1c1 + m2c2 ) ? Homework Equations T = ( m1c1T1 + m2c2T2 ) / ( m1c1 + m2c2 ) The Attempt at a Solution
  11. Richie Smash

    Find the temperature of Liquid A after 12 minutes

    Homework Statement A liquid A initially at temperature T1= 28.4°C, is heated by an immersion heater in container. The resulting temperature T2 is recorded at 1 minute intervals and the following results obtained. (I will post a picture) (a) Complete the table by computing temperature changes...
  12. quasarLie

    Calculate Average Temperature of Planet in 0.4 AU Orbit: Albedo 30%

    Homework Statement We consider a planet in a circular orbit around a star. I have to calculate the average temperature knowing that the radius of the orbit is 0.4 AU and that the planet reflects 30% of the incident light Homework EquationsThe Attempt at a Solution I used this equation F = L/4...
  13. srinaath

    Temperature rise calculation for electrical devices

    There are 2 types of temp rise measurement for electrical devices, 1)resistance type 2) thermocouple type (direct measurement) My query is 1) which method is superior and please explain me the reason. 2) Which gives higher value of measurement? Thanks in advance.
  14. G

    Finding the Condensed amount of water from a changing Temperature Airmass

    I'm currently trying to find how much water can be condensed from an airmass of a certain dewpoint if it is sent to a lower temperature. The water will be condensed over a period of time. I have the dewpoint of the initial air and the temperature of the environment where the moist air is being...
  15. D

    B Temperature of a black hole....observed from the singularity

    I'm just a layman here, who enjoys science and astronomy. I was reading about the temperatures of the cores of black holes being extremely cold, and how time at the singularity...progresses super, super slowly. But this is only as measured from an outside observer's perspective (such as from a...
  16. R

    Relationship between material resistance and temperature

    For the material used in a heater plate to generate heat for example, for a given amount of power (say 4.5 kw) does the higher resistance of the material mean it will produce a higher temperature? Or is it the other way around?
  17. Serra Nova

    Is there a highest temperature?

    I've read that there is a lowest temperature which is absolute zero where nothing happens, i.e. no vibrational activity from atoms. Is there also a highest temperature, i.e. an absolute max temperature?
  18. heavystray

    B Why Do We Use Different Pairs of Filters to Determine the Temperature of Stars?

    Hi, in determining the temperature of stars using colour index (U-B,B-V,V-R, etc), why do we need to use the appropriate pairs of filters based on their range of temperature? (this is what i read from wiki) For cool stars, we use R-I, and for hotter stars, we use B-V. I don't understand how...
  19. heavystray

    B How do you calculate the uncertainty in T using graphs?

    i have an equation like this: Given m(B-V)= 1.2 +- 0.2 How do you calculate the uncertainty in T? (btw, I solve T using graphs by finding the intersection point) My idea was first to calculate T when m(B-V) =0.2, and I then calculate T when m(B-V)= 1.2 + 0.2(its uncertainty). and then find the...
  20. AbbeyC172

    Thermodynamics: Ideal Gas Law, find the temperature

    Homework Statement A 3-ft^3 container is filled with 2-lbm of oxygen at a pressure of 80 psia. What is the temperature of the oxygen?Homework Equations pV= nRT T= PV/nR R= 10.7316 psia x ft^3/ lbmol x R The Attempt at a Solution Hi everyone! So I understand how to use the Ideal Gas Law but my...
  21. heavystray

    B Temperature based on colour index using Planck's law

    Hi, I'm trying to find temperature of stars using the stars' B-V magnitude by using the Planck law. However i do not know how to solve for T (assume other quantities are all given and determined first). Any idea how to do so? I already tried to do it but reach a dead end. Here I attached the...
  22. Evo

    Article in Nature On Global Temperature variability

    Interesting Article in Nature and looks like better news (as opposed to doom and gloom) things may not be as bad as previously predicted. It will be interesting to follow further research as we gain more data and produce more accurate climate predictions. Unfortunately, the article itself is...
  23. R

    Time to warm a volume of air to room temperature in a container

    Positing an empty container, underground, with a static temperature of 50F (both container, earth, and air temperature) and a volume of X... and introducing (and displacing) into this container a parcel of 30F air of volume Y (which is less than the volume of X)... Is there any way to...
  24. M

    Feeding temperature profile from experimental data into MAXWELL

    Hi All, my aim is to find the thermal conductivity of litz wire and also convection coefficient of litz wire and air. So, I am running experimental analysis (10A current into litz wire) and capturing the temperature of litz wire. So, I have temperature profile versus time for litz wire. Would...
  25. clembo

    Transformer exceeding its rated maximum temperature

    Homework Statement An oil-filled transformer has a c.m.r. of 500 kVA which allows it to run continuously in an ambient of 35°C with an oil temperature rise of 50°C. The transformer has a time constant of 1.5. hours and the ratio of copper losses to iron losses at c.m.r. is 1.5:1. After...
  26. P

    Study of effects of temperature on steel drilling performance

    When drilling a thick peace of steel I noticed the drill bit would cut through much faster when it was cool. The difference was minutes versus seconds! Is this a known phenomena in machining or was my drill bit simply contaminated with something or maybe other factors played a role? I've heard...
  27. lavendly

    Final temperature of the water after adding heat?

    Homework Statement You add 1500 cal of heat to a cup of water at 22.5ºC. The water has a mass of 500.0g. What is the final temperature of the water? Homework Equations Q=mcΔT The Attempt at a Solution so i tried solving it by finding the energy of the water Q=(500g)(1.0cal/g)(22.5ºC) Q=11250...
  28. P

    Calculate the temperature of neutrons emerging from a reactor

    Homework Statement A collimated beam of thermal neutrons emerges from a nuclear reactor and passes through a speed selector into a detector. The number of neutrons detected in a second with speeds in the range 4000 to 4010 m s−1 is twice as large as the number per second detected with speeds in...
  29. HelloCthulhu

    The relationship btw dielectric strength and temperature

    Wiki suggests dielectric strength is temperature dependent, but I've yet to find any math supporting this. I found some math corroborating a relationship between conductivity and temperature, but whether or not there's any causality between conductivity and dielectric strength has eluded me. Any...
  30. S

    Voltage equivalent of temperature

    How is voltage equivalent of temperature(Vt=KT/q) defined and derived? Is it related to kinetic energy(which is equal to 3kT/2)?
  31. E

    Air motor: temperature of exhaust

    I have an industrial application where 20kW of heat is being wasted, which is painful to watch. I have learned already that low temperature turbines just don't work, so would like to check some ideas and better understand how air motors/turbines work. I have also learned so far that...
  32. A

    Piston with crankshaft: what is the temperature of gas entering the cylinder?

    Homework Statement Homework EquationsThe Attempt at a Solution e) I know the temperature is lower in the transparent container but how do you represent this
  33. Luke Strand

    Finding Initial Temperature Entropy and Heat Exchange

    Homework Statement A 2.45 kg aluminium pan at 155 C is plunged into 3.58 kg of water. If the entropy change of the system is 162 J/k, what is the initial temperature of the water? Homework Equations Q = mcΔT ΔS=mcln(T_2/T_1) Q_water + Q_Aluminium = 0 c water = 4184 J/kg*K c aluminium = 900...
  34. F

    Temperature of Space: Atomic/Molecular Motion & Equilibria

    Temperature is atomic/molecular motion. However, the temperature of planetary surfaces without an atmosphere are often quoted. For example, the temperature of the lunar surface ranges from about -200 F to +200 F depending on whether or not the surface is exposed to the sun or is in shadow...
  35. C

    Which Type of Geothermal Power System is the Best?

    There are three geothermal systems that are commonly used: sry steam, flash steam, and binary cycle https://www.eia.gov/energyexplained/index.cfm?page=geothermal_power_plants . What are the efficiencies of the plants from best to least effecient on average?
  36. S

    How to calculate ambient temperature in space or in orbit?

    How would I go about calculating the ambient temperature in low Earth orbit (LEO) at approximately 400 km? What equations should I be referencing to determine the temperature of sun light side and/or eclipse side? Thanks!
  37. M

    Change in temperature for a system with entropy change

    Homework Statement I am Pretty Lost with this problem...[/B] A 2.45-kg aluminum pan at 155∘C is plunged into 3.58 kg of water. If the entropy change of the system is 162 J/K, what was the initial temperature of the water? NOTE:We did not receive a Tf for the system. Homework Equations...
  38. EastWindBreaks

    How to find specific volume given temperature?

    Homework Statement Homework Equations The Attempt at a Solution I don't understand how the solution got its values, not from the tables right? because I couldn't find such value from all of the tables. Since the pressure is less than the saturated pressure at given temperature, it is in...
  39. Vivek098

    Kelvin and Platinum Temperature Scale.

    Is it possible that Kelvin and Platinum Temperature Scale give same reading of Temperature?
  40. S

    Thermodynamics - Temperature change of Argon

    Homework Statement The temperature of n = 19 mol of argon gas is increased from T1 = 21 oC by Q = 4.4 kJ heat transfer, while the gas pressure is kept constant. What is the new gas temperature in Celsius degrees? Homework Equations and as its a monoatomic gas I think this means that the...
  41. Jamie_Pi

    Calculate Final volume and temperature of piston

    Homework Statement One cylinder in the diesel engine of a truck has an initial volume of 640 cm3. Air is admitted to the cylinder at 30°C and a pressure of 1.0 atm. The piston rod then does 500 J of work to rapidly compress the air. What are its final temperature and volume? Homework Equations...
  42. J

    I Schwinger effect verified by Unruh temperature?

    According to https://arxiv.org/abs/1407.4569, equation (2.15), the Schwinger electron-positron pair production rate in Minkowski space, ##N_S##, is given in natural units by $$N_S=\exp(-\frac{m}{2T_U})$$ where the `Unruh temperature for the accelerating charge', ##T_U##, is given by...
  43. M

    Climate Change: Why Doesn't Rising Temperature Balance Out?

    First, I am not a scientist, so this may be a stupid question. But with all the concern about global warming - and given that temperature and pressure are related - why doesn’t rising temperature cause the atmosphere to expand outward and the temperature to fall as a result, back to an...
  44. G

    Change in Temperature for Stretched Surface

    Homework Statement The surface tension of a layer of water obeys ## \sigma = a- bT##, where ##T## is the temperature. Find the change in temperaure, ##\Delta T## when the area is increased isentropically. Homework Equations ## dU = dQ -dW## , ##dW = \sigma dA##, ##dU = C_A dT + [\sigma...
  45. J

    Cooler objects able to increase the temperature of warmer objects?

    Not sure this should go here (you guys need a thermodynamics section). But there is quite the debate going on about cooler objects being able to increase the temperature of warmer objects here: https://wattsupwiththat.com/2017/11/24/can-a-cold-object-warm-a-hot-object/comment-page-1 They are...
  46. C

    Absolute zero temperature is impossible to achieve?

    Just a general musing. Could absolute zero ever be physically possible or is it like the speed of light but for an inverse reason? The speed of light take infinite energy to achieve. So therefore is impossible because the energy put into the system adds mass. This is not noticeable at slower...
  47. S

    Straight line plot of bipolar transistor - temperature?

    Hey everyone, I'm trying to plot a straight line for a bipolar junction transistor to find the room temperature, T, using my experimental results for the associated base-emitter voltage, ##{V}_{BE}## and collector current, ##I_C##. Here's the equation that I'm using: $$ I_C = α_F {I}_{EO}...
  48. S

    Solving for Final Equilibrium Temperature of Water-Copper System

    Homework Statement 173 g of water at 20°C is contained in a copper container of mass 327 g. An additional 129 g of water at 100°C is added. What is the final equilibrium temperature (in degrees C) if we treat the system's water and container as isolated? Homework Equations Q = mcΔT The...
  49. H

    Mean Earth Temperature Data: 1951-2012

    Data for the mean Earth temperatur: - For example, the average annual temperature for the globe between 1951 and 1980 was around 57.2 degrees Fahrenheit (14 degrees Celsius). (UCAR). - The global mean surface temperature is 14.46 °C computed from MODIS data (2001-2012). - Estimated Jan 1951-Dec...
  50. BillTre

    What is the Science Behind Temperature Control Fabric?

    This article in Science mag news is about a fabric that can, let more heat (via IR) out in hot weather, or flipped over, keep more heat in the cold Here is the Science article (not free). The fabric also let's gasses and humidity pass through because it has nano-pores. It has 4 layers: 2...
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