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. Decimal

    Relation between temperature and boiling point?

    Hello, I am encountering some confusion with the relation between the latent heat of vaporization and the temperature of a substance. I understand both the latent heat and the entropy change of vaporization are dependent on the temperature, assuming the pressure is held constant. However given...
  2. U

    Saturation magnetization of iron as a function of temperature

    Hi, I am looking for the temperature dependence of the saturation magnetization of Fe. Any help?
  3. J

    How to calculate color temperature?

    I am looking for calculating color temperature in the IR/Microwave scale frequencies, for room temperature, 273K, 263K, 253K, all google is showing is about visible light and about display systems.
  4. N

    Distance, Time, and Temperature question

    A person throws a rock down a well with an initial velocity of 2.10 m/s. The sound of the rock striking the bottom of the well is heard 4.22 seconds after the rock is thrown down. If the velocity of the rock just before it hits the bottom of the well is 41.0 m/s. What is: a) The depth of the...
  5. D

    At what temperature does paper catch fire?

    If there is a paper glued to cctv camera that is hot (continuous operation)... can the paper just combust? what temperature can it do that?
  6. Monsterboy

    In the context of statistical mechanics can anyone define temperature?

    I was told that defining temperature as the "average kinetic energy of the particles in a system" is not accurate enough.
  7. PlanetGazer8350

    B Can ultracapacitors be used to split CO2 into carbon and oxygen?

    I have been researching on the bonding energies of different compounds, and for example, for CO2 it is 1600kJ/mole, 1600kJ/44g, or ~36.37kJ/g of energy required to split the carbon dioxide into carbon and oxygen. Furthermore, I transformed the amount of energy required in kJ to degrees celsius...
  8. Andres Padilla

    Why this special case occurs in an exchange of heat

    Homework Statement Hello. First of all sorry about this question, it has to do a little with heat transfer from engineering. This situation is not real, I was working in a proyect and this doubt came to me. I have a heat exchanger of parallel tubes. Water flows in a tube and oil flows in...
  9. dromeascr

    What is the pressure surrounding a liquid at its boiling point?

    Hello everyone, before I start I just want to mention that I am not an expert in physics whatsoever, so please be as specific as you can get if you wish to provide an answer. (The question itself might be considered stupid to be honest) I read the definition of the boiling point recently and...
  10. vukhanh97na

    Measure temperature without a microcontroller

    Hello everyone . I'm having a project about : Use thermorcouple to measure temperature without microcontroller(0 - 200 oC) . I researched and i think : " use opamp and icl7107 for display " . But i have 2 problem : - I can't amplify exactly signal from thermorcouple (because it's very small ~uV)...
  11. space unicorn

    Can temperature keep rising without limit?

    I'm curious...
  12. H

    Melting time vs Temperature and Mass

    I recently saw the movie “Man of Steel”. In Superman’s fight with Zod, Superman cuts (by melting) a steel I-beam, that Zod is about to hit him with, with a swipe of his heat vision. To melt steel that fast (under 3 seconds) requires a large temperature. My question is how can we calculate the...
  13. GhostLoveScore

    Calculating average daily temperature

    I have a automated weather station and I'm collecting data from it. And I was wondering about something. I calculate average daily temperature like this: (T07+T14+2*T21)/4 . During the summer I am calculating it like this (T08+T15+2*T22 )/4 . That's taking into consideration daylight saving time...
  14. C

    I Temperature limits on Debye's Calculationp

    Debye assumed sound wave dispersion relation for phonons(##ω=vK##) and this corresponds to acoustic modes in low frequency limits. That's why it explains low temperature heat capacity fairly well. But how could this also explain high temperature limit(##C=3k_B## per atom)? I know Debye...
  15. Krushnaraj Pandya

    Change in temperature when a gas is in a moving container

    Homework Statement Some gas at 300K is enclosed in a container. Now the container is placed on a fast moving train.is the change in temperature of the gas the same as the change dT observed when train suddenly stops? Homework Equations 1/2mv^2=dU?? or dU=0?? The Attempt at a Solution...
  16. T

    Why doesn't the temperature of water slightly decrease during boiling?

    When you heat a pot of water why wouldn't the water temp decrease slightly when it starts boiling? Isnt boiling a type of evaporation? In evaporation the molecules near surface have enough KE to escape into the gas phase, which then lowers the T of the remaining liquid. That is how sweating...
  17. D

    Temperature as a function of time in black body radiation

    Homework Statement 2. Consider a metal sphere of radius R and heat capacity C, initially at a temperature To which is much hotter than the background temperature. a) Derive an analytical result for the temperature of such a sphere as a function of time. Clearly state any simplifying...
  18. negative

    Relation between boltsmann/gas constant and temperature

    so i have been trying to calculate boltsmann constant by assuming the fact that for an ideal gas the equation : PV=nRT is true. i assume that for containing each molecule the wall needs to apply a force. now here is where it get's a little weird. each molocule should be only deflected in the...
  19. T

    Seawater sample temperature control – heat exchanger design

    I’m designing a system where a sea water sample must have its temperature controlled between near its freezing point (-2°C) and +30°C to simulate sea temperatures. To control it, the sample will be in contact with a block, which will be controlled by an external circulating water bath. The image...
  20. Phil31

    Temperature and Pressure Calculation

    Hi there, New to the forum. I decided to come here as I am currently working on a formula that will give me the resulting pressure as a result of an increase in temperature within fixed volume. I have used Charles Law and Boyles law and combined them in a way that gives me this increase...
  21. M

    Temperature drop in an insulated pipe over 12 hours

    Hello all, I have been having some problems and would appreciate any help: I have a length of insulated pipe filled with engine oil at rest, the variables are as follows: Toil: 40 oC Tair: 5 oC h1 (LO): 3600.63 W/m2/K r1 (pipe inner): 0.1 m r2 (pipe outer): 0.1095 m r3...
  22. F

    Infrared Cameras Spectral Range and Derived Temperature

    Hello Forum, I am wondering why infrared cameras can only detect radiation between 1micron to 15micron. This clearly depends on the sensor's material. Based on Wien's law, this corresponds to temperatures from -79C to 89C. Are infrared cameras only detecting within this spectral range because...
  23. S

    When does gas do more work: constant pressure or temperature?

    A quantity of ideal gas undergoes an expansion that doubles its volume. Does the gas do more work on its surroundings if the expansion is at constant pressure or at constant temperature? The answer in the book says W at constant temperature gives a greater value for the given case. But when I...
  24. BlackJ

    When to convert units of temperature?

    Homework Statement [/B] (1)A sphere of radius 0.500 m, temperature 27.0 C, and emissivity 0.850 is located in an environment of temperature 77.0 C. At what rate does the sphere (a) emit and (b) absorb thermal radiation? (c) What is the sphere’s net rate of energy exchange? (2)A cylindrical...
  25. A

    Dielectric constant of air with temperature change

    I'm looking to see how much the dielectric constant of air will change mostly as a function or air temperature. Is there a formula that outputs air dielectric as a function of temperature or atmospheric pressure?
  26. T

    Cannot find the Temperature Change inside of a Tank

    It seems that a solution to the following problem is strangely absent from the internet. After days of research, I have found no one who offers such a solution. Only one paper addressed it but was sloppy in the way it presented the equations; they were incomplete. The problem is simply...
  27. A

    Effects of Temperature on Flow Rate

    Using a pump we are cycling water through a capsule with filter media inside; while measuring the flow rate (l/min) and the pressure (psi) going in and the pressure going out. The water is cycled back into the same storage tank. As the flow rate increases the differential pressure should change...
  28. N

    Calculating Temperature of Radiation at t1

    If there was background radiation of say 1.95K what would be the correct way to calculate the temperature of radiation at t1? Do we need to know what t1 is and also i have looked at Stefan Boltzmann law but i do not think that formula would be appropriate for what is trying to be achieved here.
  29. Richie Smash

    What will the final temperature of the coffee be?

    Homework Statement 150g of milk at 10°C is added to 150g of hot coffee at 80°C. Assume they have the same specific heat capacity. The temperature of the coffee decreases: A: to 35 °C B: to 70°C C: by 70°C D:by 35°C Homework Equations Eh= mass x (c) x ΔT Where (c) is specific heat...
  30. K

    Heat Question -- Temperature rise of a hiker on a long hike

    Homework Statement A 80.4 kg hiker uses 212 kcal hr-1 (3 s.f.) of energy whilst hiking. Assuming that 20% of this energy goes into useful work and the other 80% is converted to heat within the body, calculate the temperature change, in units of Kelvin (K), of the hiker's body during a 1.6 hour...
  31. B

    Thermodynamics - temperature, pressure and heat

    Homework Statement The initial state of 0.1 mol of an ideal monatomic gas is P0=32 Pa and v0=8m3. The final state is P1=1 Pa and V1=64m3. Suppose that the gas undergoes a process along a straight line joining these two states with an equation P=aV+b, where a =31/56 and b=255/7. Plot this...
  32. S

    Bending light with temperature gradients

    A quick question about this type of apparatus. The apparatus itself is composed of 2 concentric hollow cylinders. The cylinder at center is cooled below -50C. The atmosphere around the outer cylinder is at room temperature. This creates a temperature gradient in the space between the cylinders...
  33. M_Abubakr

    Using Pressure and Temperature differences to find height

    Homework Statement At the top of a mountain the temperature is -5 degree C and a mercury barometer reads 566 mm, whereas the reading at the foot of the mountain is 749 mm. Homework Equations Assuming a temperature lapse rate of 0.0065 K/m and R = 287 J/kg K, calculate the height of the...
  34. T

    Butanol at a temperature of 28 C is pumped at a velocity of....

    Homework Statement Butanol at a temperature of 28 C is pumped at a velocity of 14 m s-1 through a 100 mm diameter tube kept at a wall temperature of 90°C. The properties of butanol are given below. Determine the convective heat transfer coefficient (you will find the appropriate correlation...
  35. A

    Viscosity & Temperature - Linearisation and glycerine?

    Hey all, I'm new to the forums and had a quick question: (please tell me if this is the wrong topic under which I posted, please move it if needed! @mods) I am doing a lab report investigating the effect of temperature (˚C) on the dynamic viscosity (Pa s) of glycerin. I am timing the time it...
  36. E

    How do I calculate the gauge pressure?

    Homework Statement An automobile tire is pumped up to a gauge pressure of ##2.0 \times 10^5 ## Pa when the temperature is 27◦ C. What is its gauge pressure after the car has been running on a hot day so that the tire temperature is 77◦ C? Assume that the volume remains fixed and take...
  37. H

    Heat and work when temperature increases by 1 degree

    Homework Statement Kinetic energy per mol is 3/2KTHomework Equations Q = nC##\Delta##T U = Q + W W = -P##\Delta##V The Attempt at a Solution 1) internal energy = 3/2NKT 2) heat needed to increase temperature of 1 mol ideal gas by 1 degree at constant volume? Since constant volume, W = 0 Q =...
  38. H

    Does the initial temperature affect the change in temp?

    Say I dissolve NaOH in water - a very exothermic reaction. Does it matter if I dissolve it in water that is at room temperature or at a different temperature? Will changing the initial temperature of the water affect the dH of the reaction (hence affect the change in temperature at the end of...
  39. G

    Real-time engine simulation - oil temperature

    Hi folks! A while ago, we discussed a real-time simulation of an oil cycle within a combustion engine. Back then I was focusing on volume flow and pressure and you were incredibly helpful in coming up with the required formulas, so thank you again for your help! I'm now moving to the next...
  40. B

    What is the correct solution for the temperature expansion problem?

    Homework Statement A steel container is filled with alcohol. For how much kelvins we have to raise the temperature for the pressure to be raised by 6 bar? Compressibility of alcohol is \kappa=1.15 \cdot 10^{-4} bar^{-1} temperature coefficient of volume expansion of alcohol is \beta_a=...
  41. Y

    Temperature multiplied by Power?

    Homework Statement I'm trying to come up with a situation, perhaps in a mathematical calculation, or characteristic describing physical phenomena that is related to temperature times power. I know that thermal conductivity is measured in temperature divided by power, but unsure of a scenario...
  42. P

    The effect of exit pressure and temperature on a turbine

    I still struggle with the interchangeability of pressure and temperature and how they affect the performance of various bits of turbomachinery. Microscopically they're very interconnected, in that the measure of pressure is the result of the confinement of the measure of temperature, however...
  43. J

    I How does the Higgs scalar potential evolve with temperature?

    How does the Higgs scalar potential evolve with temperature? Is there possibility they are independent? Besides temperature. What else can theoretically affect the higgs scalar potential?
  44. DariusP

    How did H.K. Onnes measure temperature and resistivity?

    How did H.K.Onnes measure temperature and resistivity? As you know, Onnes is a dutch physicist that was the first person to liquefy helium and discover superconductivity a year or so later. I am wondering - what equipment was he using at that time? I couldn't find this information anywhere...
  45. DrClaude

    Fermi temperature of a 1D electron gas

    Homework Statement Consider a one-dimensional metal wire with one free electron per atom and an atomic spacing of ##d##. Calculate the Fermi temperature. Homework Equations Energy of a particle in a box of length ##L##: ##E_n = \frac{\pi^2 \hbar^2}{2 m L^2} n^2## 1D density of states...
  46. O

    Temperature profile inside a pellet

    Hi, As some of you may know, the temperature profile inside a pellet is determined by using the equation given below, Tx=TRim+ρ(rpellet2-x2)(4Kf)-1 Where; ρ is power density. Kf is thermal conductivity. The temperature profile is strictly dependent on the material used as a fuel. The...
  47. J

    I Unruh temperature in gravitational field

    According to the Unruh effect an observer who is has an acceleration ##g## will observe the temperature of the vacuum to be $$T=\frac{\hbar g}{2 \pi c k_B}.$$ According to the equivalence principle the observer should measure the same Unruh temperature if he is sitting on a planet whose surface...
  48. C

    How much heat in joules is needed to raise the temperature

    Homework Statement How much heat in joules is needed to raise the temperature of 7.0 L of water from 0°C to 78.0°C? (Hint: Recall the original definition of the liter.) Homework Equations How much heat in joules is needed to raise the temperature of 7.5 L of water from 0°C to 87.0°C? (Hint...
  49. A

    Using an IR Thermal Gun to check for steam passing valves

    Greetings I am asking about the reliability of using a thermal gun to check if there is passing downstream the valve. The fluid is either steam or air. Wouldn’t the pressure and temperature drop sharply downstream the valve if it is closed but passing ? again I am talking about air or steam...
  50. B

    Change of Temperature from Work in Hydrostatic System

    Hi, I have a little conceptual question. I have an idea about the topic, but I would need to formalize it a little bit. The problem is the following: Imagine the following scenario: You put a little bit of water in a bottle, you assure yourself that everything as at a constant temperature and...
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