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. Chromatic_Universe

    A Equilibrium recombination temperature for Helium

    How to get to the expression for equilibrium recombination temperature for Helium?
  2. R

    What is the final temperature of the air in a tube

    Homework Statement I have a copper tube with outer radius r2 and inner radius of r1. Half the tube is exposed to the surrounding air while the other half is embedded into the ground. The outside air temperature is T2 and the ground temperature is T3. What is the air temperature inside the tube...
  3. Edge5

    The thermal speed of an electron at room temperature

    I am trying to find the thermal speed of electron at room temperature. kT = (1/2)mv^2 which gives v=√((2kT)/m) but answer says it should be √((kT)/m) Where did that 2 go?
  4. H

    Probability at a temperature T that a system has a particular energy

    Salutations, I'm starting in statistical mechanics and reviewing some related studying cases I would like to understand what occurs in small systems with normal modes of vibration, for example, a small system that has 2 normal modes of vibration, with natural frequencies $$\omega_1$$ and...
  5. dwight_v

    Final temperature for two blocks of iron placed in contact

    Homework Statement Two blocks of iron, one of mass m at 10.0C and the other of mass 2m at 25.0c, are placed in contact with each other. If no heat is exchanged with the surroundings, which of the following is the final temperature of the two blocks? A)10 B)15 . D) 20C ( this is the answer) The...
  6. DracoMalfoy

    How Do the Temperatures of Star 1 and Star 2 Compare?

    Homework Statement Star 1 emits energy at a rate that is 2 times that of Star 2. If Star 1 also has a radius that is 3 times larger than Star 2, how do the temperatures of the stars compare? a. Star 1's temperature is 2.58 that of Star 2. b. Star 1's temperature is 3.75 that of Star 2. c...
  7. B

    Temperature Measurement: Are All Thermometers Created Equal?

    What is the difference in temperature with different thermometers for the same object? Thanks !
  8. T

    Mean Rating Temperature for insulation in ASHRAE

    Hello, Can someone please tell me what the mean rating temperature in the tables provided in ASHRAE fundamentals, ASHRAE standard 90.1&90.2 for chilled water insulation indicates.
  9. A

    What is the correct way to find the temperature of helium in this scenario?

    Homework Statement Helium is kept in a pressure vessel at a pressure of 5.42 bar and the resulting density is 0.92 kg/m3. The gas constant R is 8.314 J/(mol*K). The volume of the vessel is 1589.194 m3. I need to find the temperature of helium in Celsius. Homework Equations...
  10. Graeme M

    B What does it mean to say that "space" has a temperature?

    I was thinking about the fact that space contains all sorts of matter and that these objects have temperatures. But then I read that space itself has a temperature depending on where you are. The cosmic background radiation for example has a temperature of 2.7K. Can someone explain what that...
  11. bbbl67

    I Calculating the Sun's core temperature?

    Knowing the following information: Sun surface temperature of 5788 K, Sun's core is between 20-25% of radius. I tried to (perhaps naively) calculate the temperature to the edge of its core from the surface temperature, using an inverse square law. Depending on which value you use for the core...
  12. P

    Black Hole Temp: Calculate Specific Heat

    Homework Statement Compute the specific heat of black hole Homework Equations ##T=\frac{2}{r_+}-3/2048 r_+^2-\frac{6r_+^3M^2}{(M+r_+^6)^2}## ##f(r)=1-\Big (\frac{r^2}{64}+\frac{Mr^4}{M+r^6} \Big ) ^{1/2}## ##r_+## is the horizon where ##f(r=r_+)=0##. The Attempt at a Solution I tried to...
  13. YMMMA

    PV diagram/ which labeled process has no temperature?

    Homework Statement I have had a question in my quiz that I don’t remember very well, but here’s a diagram and there’s no need for numbers in axis because it’s a concept- based question with no calculations. The question asks if an ideal gas system moved from A-B-C-A. Where is the process by...
  14. O

    Liquid temperature increases when flowing through a 100% efficient pump?

    Hi, For an ideal Rankine cycle, the temperature-specific entropy diagram can be given as follows, The pump in this cycle is isentropically 100% efficient. My question is that why the temperature of the water increases as it flows through the pump (point 1 to 2) if the pump is 100%...
  15. A

    How to calculate the refractory wall temperature?

    Homework Statement A gas-fired tube heater has the following data: Dimensions of the combustion chamber: 15 * 20 * 40 ft Tube outside diameter: 5 in Temperature of the tube=800° F Center to center spacing: 8 in Number of tubes (arranged in a single row of which 6 tubes are shield tubes) ...
  16. R

    Temperature profiles and thermal resistance

    I heated two different materials with a laser beam for about 10 seconds and these are the measured temperature profiles: From the various solutions to the general heat conduction equation, temperature rise seems to increase with increasing thermal resistance of the material. The total...
  17. Krushnaraj Pandya

    Brightness change with temperature

    Homework Statement A black and yellow body at room temperature are thrown into a furnace at very high temperature. How will the initial and final brightness of both compare? Homework Equations λT=constant The Attempt at a Solution The rise in the black body's temperature will be higher...
  18. Krushnaraj Pandya

    Change in radiation with temperature

    Homework Statement What would be the increment in heat energy radiated when the temperature of a hot body is raised by 5%? Homework Equations P=σεAT^4 The Attempt at a Solution dP/P=4dT/T dT=5 when T is 100 initially. Let's assume P was also 100 initially for convenience, therefore dP should...
  19. Krushnaraj Pandya

    Heat capacity and temperature problem

    Homework Statement A piece of metal is heated by supplying a constant power P. The temperature of the metal starts varying as T=kt. The heat capacity of the metal as a function of temperature is? Homework Equations Q=CdT The Attempt at a Solution From Q=CdT, dT is k, since P is Q/t, I plugged...
  20. J

    Calculate the final temperature of the mixture

    Homework Statement Consider the following reaction. 2 HCl(aq) + Ba(OH)2(aq) BaCl2(aq) + 2 H2O(l) ΔH = -118 kJ Calculate the heat when 100.8 mL of 0.500 M HCl is mixed with 300.0 mL of 0.450 M Ba(OH)2. Assuming that the temperature of both solutions was initially 25.0°C and that the final...
  21. J

    Calculate the final temperature of the solution

    Homework Statement Consider the dissolution of CaCl2. CaCl2(s) Ca2+(aq) + 2 Cl-(aq) ΔH = -81.5 kJ A 10.6-g sample of CaCl2 is dissolved in 109 g of water, with both substances at 25.0°C. Calculate the final temperature of the solution assuming no heat lost to the surroundings and assuming...
  22. H

    A Metal or Insulator: Examining Resistance in Multiple Directions

    Generally, a material is metal or insulator is simply determined by the gap. But if we view it in another way, to measure the resistance in different direction, says x and y, and there are usually different. And then measure the resistance change with temperature. Usually, the resistances goes...
  23. anorlunda

    Automotive How does AC temperature control work in my Toyota Camry?

    When I use the air conditioner in my Toyota Camry, and I move the temperature control towards warmer: Does it make the AC cycle on/off thus saving fuel? Does it mix warm air with the cold, thus saving no fuel? I couldn't find an answer to this on Toyota forums.
  24. Sebastiaan

    Nitrogen Oxidizing properties at high temperature

    DiNitrogen is very unreactive due to the tripple bond it has, but what happens if it heated to very high temperature and bonds are broken? does it start behaving as a strong oxidiser. I could not find iinformation on at which temperature this happens but let's assume 3500K in a Tunston reactor...
  25. hagopbul

    Are there other variables that control climate change?

    Hello all It's been a while ,as I read the almost daily news on climate change , some question come up to my mind , dose the ionosphere has any effect on climate change , as we all know now the Earth magnetic field is weakening ,and the temperature is rising ,dose this two variables related to...
  26. SchroedingersLion

    Some questions about heat and temperature

    Hi guys, I am currently working through a book about thermodynamics and statistical mechanics as I was not so great in these course during my undergrad studies. First question: The book introduces heat as the kind of energy that terminates the temperature of a system. In other words: Give heat...
  27. Lami

    Newton's Cooling Temperature formula problem

    *Given Newton's Cooling formula, where T(t) predicts temperature, and where Te is the temperature of the enviornment, T[0] is the temperature when t = 0: T(t) = Te + (T[0]+Te)e^-rt predict Te when T(120)= 86.632 T(240) = 79.210 r = 0.001 I don't know how to even remotely go about solving...
  28. T

    Calculating Laser Power from Temperature Rise, Time, and Target Mass?

    Hi Everyone! There is a type of CO2 laser cutter power meter on the market (Product link removed) The meter uses a block of black anodized aluminum bonded to the end of basically a mechanical meat thermometer, and has a zero adjustment on the back of the face to set the base temperature to...
  29. KristinaMr

    Solving for Temp Change of Epoxy Frames for Lenses Insertion

    Homework Statement This is the problem. A pair of eyeglass frames is made of epoxy plastic. At room temperature (20.0°C), the frames have circular lens holes 2.20 cm in radius. To what temperature must the frames be heated if lenses 2.21 cm in radius are to be inserted in them? The average...
  30. P

    Amount of water spilled when the temperature is changed

    Homework Statement A glass bottle of nominal capacity 250 cm3 is filled brim full of water at 20oC. If the bottle and content are heated to 50oC, how much water spills over? (For water, β=0.21X10-3 K-1. Assume that the expansion of the glass is negligible.) Homework Equations (dv/dT)/v =...
  31. Y

    MHB When the temperature when degree Celsius is equal to degree Fahrenheit

    Q7, b is where I got stuck
  32. R

    Volume and temperature rise in tissue

    I am looking for an explicit equation that shows that a sample with lesser volume will reach higher temperatures when irradiated than a sample with a larger volume. The samples in my project are biological tissues which are being irradiated by a laser. In my experiment, using a thermal camera I...
  33. P

    What is the Fahrenheit equivalent of 62.0 °C?

    Homework Statement Convert 62.0 °C to Fahrenheit Homework Equations °F=1.8(°C) +32 The Attempt at a Solution °F=1.8(62.0) + 32 = 143.60 I am confused on the significant figures for the answer. Does the temperature equal 143.6°F because 32 is an exact number? Or 144°F because 32 is not...
  34. T

    Pressure and temperature due to frictional or momentum input

    Hi, I have a hypothetical question: We have a fan which has no internal dissipation - electrical or mechanical. The fan is made to run in an adiabatically sealed room. The internal energy of the air in the room increases due to work input. This work input increases the temperature and...
  35. A

    A Critical current vs critical temperature at different fields

    Hi, I am trying to figure out whether there is a way to express the ratio of the critical current of a superconductor at zero and finite magnetic fields [denoted as Ic(0) and Ic(B)] as a function of the ratio of corresponding critical temperatures [denoted as Tc(0) and Tc(B)]. According to...
  36. T

    Carnot Cycle efficiency, temperature dependency

    Hi, We know that a heat engine working on a Carnot Cycle the efficiency is: 1 - QL/QH = 1 - TL/TH where T is in Kelvin. But if we use a different absolute temperature scale whose values at TH and TL are different, then the value of efficiency also changes. I am confused about this issue...
  37. G

    Relation Between Entropy and Temperature

    Homework Statement [/B] Strap in, this one's kind of long. (This problem is from 'Six Ideas That Shaped Physics, Unit T' by Thomas A Moore, 2nd edition. Problem T6R2.) Imagine that aliens deliver into your hands two identical objects made of substances whose multiplicities increase linearly...
  38. R

    Automotive Automotive MAF sensor vs temperature

    I'm working on a DIY EFI system for automotive use. I have a question about the mass air flow sensor operation. I know they measure the volume of air passing thru them. But the question is whether that measurement needs to be corrected for air temperature or if the MAF sensor does that by...
  39. J

    B When Difference between Kelvin and Celsius are negligible

    This question is more for practicality than anything else, and I realize it may be partly subjective. At what temperatures can the 273 degree difference between Kelvin and Celsius scales be ignored? I'm thinking for examples regarding stars and very high temperatures. Surely once you get to 15...
  40. alijan kk

    An inflated tyre suddenly bursts -- What is the temperature of the air?

    Homework Statement An inflated tyre suddenly bursts. As a result of this the temperature of air (a)increases (b) decreases (c) may increase or decrease (d) remains constant. Homework EquationsThe Attempt at a Solution The answer in the book is (D) remain constant. Does it mean air outside the...
  41. diegzumillo

    A Confusion with finite temperature and lattice formulation

    I think the title sums up pretty well my doubts. I learned QFT from Peskin and Schroeder and other common sources, all implicitly defined QFT at zero temperature. Then I started learning about lattice QCD, how to define the action, how to find continuum limits, the importance of the dependence...
  42. R

    Difference between color / temperature?

    What is the difference between a red object at room temperature and a heated red object (Metal for example). They are both red except one is cooler then the other? Why aren't the red objects in my room not hot like the heating of a metal?
  43. S

    Explaining Temperature Increase with Antenna and Tissue

    Hi; Let's imagine that I have an antenna and a biological tissue. The antenna emits the frequency of 1e7 Hz and I have a temperature increase x. When the antenna emits the frequency of 3e7 and 6e7 Hz the temperature increase is the same. How can I explain?
  44. C

    Temperature change in a metal due to heat from a distant animal?

    In bolometers, incoming radiation warms a strip of material. this material will have a large thermal coefficient of resistance, leading to a (small) resistance change in the material. the inventor, Samuel Pierpoint Langley apparently used this to detect a cow from 1/4 of a mile away using a...
  45. K

    Electronics Temperature Sensing to Switch on/off an Induction Heater

    Hello, I'm having trouble thinking of ways that I can measure the temperature of an object that I am heating using an Induction Heater. A little background: The coil and workpiece will be submerged in liquid, and due to most thermometers being metal it won't work with the induction heater. I'm...
  46. J

    Temperature change in a vacuum?

    Hello, I'm currently taking some summer classes at my college and was assigned a project to transport vaccines from one location to another (travel time ~2-5 hours.) We have to keep the vaccine within the range of 35-46 degrees Fahrenheit at all times. My group and I came up with the idea of...
  47. DaynaClarke

    Finding b in Van der Waals Equation?

    I've got a question that requires me to use the Van der Waals equation in the form: p(V-b)=nRT The process is isobaric, the volume changes from 1m3 to 2m3, and there is 1 mole of the unidentified gas. Ultimately, I need to find initial and final values of T. So I rearranged the formula...
  48. BadgerBadger92

    How does temperature play a role in nucleosynthesis?

    How does temperature play a role in nucleosynthesis? I am studying the Big Bang, and am wondering how the first hydrogen atoms were made. This is a basic question, and am wondering how they were made.
  49. S

    Analogies between temperature and time in thermodynamics

    Looking through the book of abstracts for «XXI International Conference on Chemical Thermodynamics in Russia (RCCT-2017)» I came across the abstract of talk given by Peter Atkins (University of Oxford) titled «Thoughts about thermodynamics» (you'll find the whole abstract at the end of the...
  50. kolleamm

    What material changes temperature fast?

    What sort of materials or elements heat up really fast but also cool down fast as well? Thanks in advance
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