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. J

    Finding temperature change, thermodynamics first law

    So I calculated the final and initial pressures using the given eqns, ended up with the final pressure of 96629 and initial pressure of 62639. Then I used the PV=nRT eqn to calculate the final and initial temperatures. T=P*V/(n*1.5*R). I got an initial temperature of 81.79 and a final...
  2. J

    Find rate of temperature change using heat capacity, density and area

    So first I found rate of heat change using the above equation, with T=883K, e=1, SA= 6*l^2=21.66 Now dQ/dt=746593.71 W Now I am not sure entirely what to do next. They give density so I likely have to get the mass from that, M=pV,=1.9^3*4037=27689.783 kg. My issue is that I don't know how to...
  3. J

    Calorimetry - finding the final temperature of a system of ice and water

    So all of the ice melts and I am guessing it then warms some so Q=mL+mc(change in T) for the water that cools down Q=mc(change in T) Q_cold = -Q_hot so -mc(Tf - Ti) = mL+mc(Tf - Ti) My issue is that I have 2 unknowns. I don't know the specific heat capacity of water and I don't know the...
  4. J

    Linear Expansion - Finding temperature

    So if I am understanding the question correctly, I need to find the change in temperature that causes one rights outer radii to be the same as another rings inner radii. Now what I tried is two equations change length_1= a_1*original length_inner * change in temp change length_2= a_2*original...
  5. willDavidson

    Measuring Temperature of PCB Via

    I am interested in measuring the temperature of a PCB via. Since vias are so small, I'm not sure how to go about this. Are there any methods for doing this? If I use a thermocouple, I would need to adhere it to the via wall somehow. Let's just say my via is 0.5 mm? The via would probably be...
  6. I

    Chemistry What is the relationship between temperature and reaction rate?

    I think I should use ln(K2/K1)=Ea/R(1/T1 - 1/T2), and find K2/K1. I am given T1 and T2, but not Ea. I'm not sure how to continue. Thanks. (note: the answer is C)
  7. A

    I What is a "temperature distribution" in a stellar photosphere?

    What is a "temperature distribution" in the context of a stellar photosphere and How is the temperature distribution related to the effective temperature?
  8. AleksW

    What is the temperature change of a bullet upon impact?

    Summary:: What is the temperature change of a bullet upon impact. I have this problem to solve but I'm kinda stuck, would apricate any feedback. We fire a silver bullet with a muzzle speed of 200 ms−1 into a sack of sand. What is the temperature change of the bullet, if 40 % of its kinetic...
  9. P

    Temperature difference by Dimensional analysis.

    Attempt at solution: I wanted to try and solve this with dimensional analysis. I reasoned that I would chose the following dependent variables: - [V] : Volume ( of the block) - [Q] : Heat ( the radioactive decay would cause some heating of the water) - [R]: Radiation - [Cv]: Heat capacity...
  10. ayans2495

    What is the Relationship Between Work and Temperature Change in Melting Ice?

  11. ayans2495

    Calculating initial temperature of iron block submerged into water

  12. L

    Wave frequency, medium and temperature

    Hi hi, I'm looking into how temperature affects waves, but I don't know too much about this, in how temperature mixes with all of this, I have this questions: We have a particle vibrating at frequency ##f## at a certain temperature ##t_p##, and a medium with other temperature ##t_m1##. If the...
  13. R

    MATLAB Plotting Reaction Rate vs Temperature with MATLAB

    I know how to get fusion cross section plots from the exfor website but now I need to plot the reaction rate as a function of temperature. According to the image, I have sigma and E values as x and y data. How do I integrate using MATLAB .
  14. ayans2495

    Finding the final temperature of a mixture of ice and steam

  15. DaveE

    How does temperature affect solutions?

    - Why can I dissolve more salt in hot water, than cold? - Why does more air dissolve in cold water than hot? - What about non-polar solvents? Is it the water or the solute that does this? - Are there combinations that do the opposite of the normal solid/gas dichotomy? If you want me to...
  16. jdawg

    Total Emissivity as a Function of Temperature (Ceramics)

    Hello, I’m trying to better my understanding of how the total emissivity changes with temperature for ceramic materials. Currently it is my understanding that non-metals typically have a high emissivity. A sanded surface will result in a higher emissivity, and that spectral emissivity varies...
  17. hagopbul

    Freezing temperature of vaccines

    Hello all: I have this question , as we all watch the vaccine of Covid-19 reach the market I had this question if the storage temperature of this vaccine is between -20 c to -70c Why the nano droplets in this liquid do not create ice the liquid is not freezing under that conditions although it...
  18. E

    Linear expansion of steel versus copper with increasing temperature

    Here I'm going to show all that I've understood - 1. 2. 3. What I've attempted - L = Lo (1+ α * ẟT) ẟT = 150°C - 15°C = 135°C (Steel) L = ẟL (1 + 11 * 10^-6 * 135) (Copper) L = ẟL (1 + 17 * 10^-6 * 135) This doesn't get me anywhere, obviously. Am I supposed to understand from the...
  19. bagasme

    Why We Learn Reaumur Temperature Scale in High School Physics

    Hi, In high school physics I learned how to convert between Celcius, Fahrenheit, Kelvin, and Reaumur scale of temperature. While the first three scales are highly used, why do we learn the fourth scale (Reaumur) when there aren't any practical use of it? Just for formality? Bagas
  20. PhysicsTest

    Increase in conductivity of intrisic germanium with temperature

    The intrinsic concentration ##n_i## varies with T as ##n_i^2 = A_0T^3e^{\frac{-E_{G0}} {kT}} ## ---> eq1 The mobility ##\mu## varies as ##T^{-m}## over a temperature range of 100 to 400K. For Germanium, m = 1.66 (2.33) for electrons (holes) as per book. The conductivity is given by ##\sigma =...
  21. J

    A Temp of Moving Body: 110 Yrs of Debate | Current Tech Update?

    According to this scientific report ( https://www.nature.com/articles/s41598-017-17526-4 ) written in 2017 : " The construction of a relativistic thermodynamics theory is still controversial after more than 110 years. To the date there is no agreement on which set of relativistic transformations...
  22. 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 =...
  23. 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)...
  24. 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?
  25. 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...
  26. 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..
  27. 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 ?
  28. 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...
  29. 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.
  30. 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...
  31. 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...
  32. 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...
  33. F

    Boiling & Critical Temperature: Understanding The Difference

    Are boiling temperature and critical temperature the same or they are different things?
  34. 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...
  35. 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)...
  36. 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...
  37. 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...
  38. 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...
  39. 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.
  40. 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...
  41. 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?
  42. 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...
  43. 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...
  44. 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...
  45. 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...
  46. 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...
  47. 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...
  48. 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...
  49. 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 =...
  50. 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...
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