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.

View More On Wikipedia.org
Recent contents Top users
  1. K

    Calculation of the rise in the temperature of a truck brake

    The text gives the answer as 92ºC. The answer is arrived at by doing ##Q=Mgh=mc\Delta T##. But it is unclear to me if they are the same. I checked the coefficient of friction and it definitely seems to be considerable. Is the entire PE lost by the truck going to result in increasing the...
  2. Ale_Rodo

    I Why is Entropy defined as a fraction of heat over temperature?

    Can we make sense out of the formula of entropy like we do for density (like "quantity of mass per unit volume")? What's the sense of Q/T? Couldn't it be something else? Of course it probably is a 'me-problem', but I haven't studied Thermodynamics deeply yet and was wondering what Entropy...
  3. O

    Simulation Code for Earth's Historical Temperature Record

    I am new to the field of climate change. Are there publicly available simulation code for Earth's temperature history, going back, say 2000 years, with a resolution on the order of years? Thank you very much.
  4. S

    Does Resistance change wrt temperature include effect of size change

    Changing the temperature of a metal changes the resistivity. But It also changes the size of a sample under test. Does the change in size have an additional effect on the resistance or is that already factored in ?
  5. U

    B Physical temperature and antenna temperature

    I have read some documents on the subject, but until now, unfortunately, I still do not have a good understanding of them, most likely due to personal shortcomings that start from physics. In this regard, I would like to try here to expose some doubts that will almost certainly appear very...
  6. ikihi

    I Compressing gas with piston: reasons for temperature increase?

    So when volume decreases, pressure increases according to Boyle's Gas Law and the ideal Gas Law. In other words, compressing gas into a smaller volume increases the vapor pressure. And also, According to Gay-Lussac's Law and ideal Gas Law, when pressure increases on a gas, temperature also...
  7. AppleiPad556

    Correlating albedo with temperature?

    As mentioned above, I wanted to devise an equation that can relate the colour of a surface to the temperature on the surface. I tried using the general definition of albedo and combining it with the Stefan-Boltzmann equation (see above, Relevant Equations). However this means that the higher the...
  8. C

    B Cooling the room with a ceiling fan and skylight window

    Hello, So I know that a ceiling fan either operate clockwise (winter mode) or counter-clockwise (summer mode) and while the fan is meant for just moving air around, I'm wondering if utilizing a ceiling fan and an opened skylight window only a few feet near the ceiling fan would help move the...
  9. Poetria

    Multivariable temperature variation while swimming in a hot spring

    I have computed ##T_x## and ##T_y## and evaluated it at the point (20, 20). ## \frac {-450*x}{x^2 + y^2 + 1)^(\frac {3} {2}} - \frac {420*(x + 10)} {(x + 10)^2 + (y - 20)^2 + 1)^(\frac {3} {2}}, \frac {-450*y}{x^2 + y^2 + 1)^(\frac {3} {2}} - \frac {420*(y - 20)} {(x + 10)^2 + (y - 20)^2 +...
  10. pixelsnpings

    Calculating temp rise caused by electric arc in an enclosed space

    Summary:: Given a known closed space/apparatus ( e.g. constant volume, pressure, density, current, temperature, voltage, spark gap distance - let me know if I missed something) how would I compute the change in gas temperature. Hello, Given a known closed space/apparatus ( e.g. constant...
  11. S

    I (See image) At what distance does the temperature of the Corona decline?

    My astronomy textbook includes this graph of the temperature of the Sun's Corona versus the distance above the photosphere. It appears to go up from 4,500 K to over 1 million K at 20,000 km above the photosphere. But at what point does it come back down? Or does it not? Does that mean the...
  12. river928323

    Maintaining Component Temperature with Water Bath

    Using water bath to maintain temperature of the component
  13. Istiak

    Calculate the volume change with gas temperature for this piston in a cylinder

    Solution attempt : Option : I am sure that my work is wrong. But, I must add solution attempt in PF that's why I just added that. How can I solve the problem?
  14. George Jones

    What Causes Extreme Temperature Swings in My City?

    Yesterday's high temperature here was 38.4C (101.1F). The early morning low on 15 Jan 2020 was -44.2C (-47.6F). In the last 18 months, my city has had a spread of actual temperatures of 82.6C (148.7F).
  15. Krokodrile

    Chemistry Work, temperature and energy in a constant pressure process

    So, the Cp and Cv its very confusing for me. But, i understand what's its happening in this process, so, i use the logic and first i obtain a ecuation for obtain the final temperature ecuaticon: Q=m*C*△T Q=m*C*(T2-T1) T2=(Q+T1)/(m*C) If the process its in constant pressure, i use the Cp valor...
  16. M

    Temperature vs moisture content to sustain a fire in a given material?

    So I've been trying to start a fire in which was successful for 10 minutes then died down due to high moisture in the leaves and branches. Which made me think of this phenomenon. is there a graph relationship to burning an organic, non-metal material that is well defined in relation to the...
  17. xpell

    Could a high / very high temperature nuclear reactor operate in Venus?

    Hi. I'm just a curious person with high-school-level scientific knowledge. However, I was wondering if a specially-engineered Generation IV high or very high temperature (800-1,000ºC) nuclear reactor could work in Venus using the local atmosphere at 450ºC as "coolant", just like a "typical"...
  18. F

    Metals as Infrared Reflectors and their Temperature

    Hello everyone. I have reading about IR radiation, reflectivity, and emissivity of materials. Metals, in general, seem to be excellent reflectors or IR radiation (they are like infrared mirrors. That said, why do they get so hot when they are left in the sun? A metal roof cannot be touched...
  19. J

    I Temperature of the Universe based on the ΛCDM Model

    Using Jorrie’s calculator we can get the following T vs. t graph up to z = 20,000: In a log-log plot the above curve is represented by the red solid line in the figure shown below: The dashed line shows results for the small a limit using the equation T = 2.725 K / a. Here are some...
  20. Dario56

    Maximum non - PV Work at Constant Temperature and Pressure and Reversi

    When we talk about systems at constant temperature and pressure, maximum amount of non-PV work can be extracted if process is carried reversibly and in that case it is equal to change in Gibbs energy of the system (decrease in Gibbs energy if system does non - PV work, A.K.A work is extracted...
  21. T

    A Photon self-energy in the finite temperature field theory (real -time)

  22. F

    Instantaneous Gas Compression: temperature increase?

    If I a have a gas confined in a certain initial volume Vin at a certain pressure Pin and at a certain temperature Tin, and istantaneously compress it down to a final volume Vfin < Vin, how do I calculate the increase in temperature? Assume I know the exact pressure curve (P vs. V). The system...
  23. J

    Relative Humidity and Temperature Changes when adding Heat

    Can anyone help me with this? -How much heat must be added to 3.5 m3 /s of moist air with a dry bulb temperature of 10°C and a relative humidity of 60% to raise the temperature of the air by 17°C? • What will be the relative humidity of the air once this heat is added? • What is the power...
  24. J

    How to calculate initial pressure and temperature - adiabatic process

    Im confused on working backwards so to speak to find adiabatic work. To find work for this adiabatic process, I either need to know the change in temperature OR the initial pressure (I think?). The issue is that I don't know either the initial temperature nor the initial pressure so I am not...
  25. D

    Calculating Hot Air Balloon Volume & Lift

    Volume of hot air ballon V=((4/3 pi R^3)/2) + (1/3 pi h (R^2 + r^2 + Rh) = 2956.24 m3 Balloon: R=9m h=15m r=1m m = 750 kg H = 5000m T = 373 K p1 = 101300 Pa p2 = 50650 Pa M(air) = 0.029 kg/mol F = mg - 7350 N
  26. Mohammad Sakib

    Why the temperature of a car does not increase with velocity?

    We know temperature is a measure of average kinetic energy of molecules/particles of a system. Now if a car starts to move, its velocity increases so does its kinetic energy. Therefore all the molecules are gaining velocity too. Shouldn't this increase the temperatre as average kinetic energy of...
  27. G

    Absolute zeros other than temperature (e.g. pressure)

    Hi. A version of the third law of thermodynamics states that no system can be cooled down to absolute zero temperature in finitely many steps. But what about other quantities, for example pressure: Is it possible (in principle) to evacuate a system up to the last gas particle, or would this...
  28. M

    The effect of temperature on phosphorescence

    I had read somewhere that as the temperature increases, its lifetime decreases. But there was no further explanation. Of course, I don't know if it's true yet.
  29. S

    Thermodynamic Axioms: Establishing Temperature, Internal Energy & Entropy

    Is the purpose of the 0th, 1st & 2nd Laws of Thermodynamics simply to legitimate the thermodynamic properties of Temperature, Internal Energy & Entropy, respectively? It seems that all these laws really do is establish that these properties are valid thermodynamic state properties and the...
  30. 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...
  31. 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...
  32. 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...
  33. 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...
  34. 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...
  35. 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)
  36. 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?
  37. 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...
  38. 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...
  39. ayans2495

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

  40. ayans2495

    Calculating initial temperature of iron block submerged into water

  41. 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...
  42. 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 .
  43. ayans2495

    Finding the final temperature of a mixture of ice and steam

  44. 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...
  45. 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...
  46. 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...
  47. 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...
  48. 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
  49. 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 =...
  50. 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...
Back
Top