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.

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  1. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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.
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. 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...
  12. 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...
  13. 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 =...
  14. Y

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

    Q7, b is where I got stuck
  15. 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...
  16. 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...
  17. 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...
  18. 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...
  19. 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...
  20. 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...
  21. 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...
  22. 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...
  23. 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...
  24. 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...
  25. 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?
  26. 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?
  27. 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...
  28. 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...
  29. 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...
  30. 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...
  31. 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.
  32. 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...
  33. 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
  34. 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...
  35. 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?
  36. 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.
  37. 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...
  38. 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?
  39. 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.
  40. 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...
  41. 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...
  42. 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...
  43. 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)...
  44. space unicorn

    Can temperature keep rising without limit?

    I'm curious...
  45. 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...
  46. 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...
  47. 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...
  48. 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...
  49. 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...
  50. 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...
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