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. T

    Time for a steel die to reach temperature

    Hello. I will be doing some experiments with boron steel. The idea is to heat a steel specimen (200x20x1,5 mm dimensions) to 950°C and then quickly transfer it from the oven to the die at room temperature. When the specimen reaches the steel die it will supposedly be at around 800°C. At this...
  2. S

    Relationship between angle of twist and temperature gradient

    Homework Statement To derive a formula to find the angle of twist when a torque T is applied and the temperature gradient is ΔT Homework EquationsThe Attempt at a Solution Angle of twist Φ=TL/JG I believe as temperature decreases, torque will increase which means angle of twist is inversely...
  3. G

    Need to find dense liquid at room temperature

    I want to know how easy it is to find or make a really dense liquid...perhaps 4000 kg per cubic meter at room temperature or lower. I need it to be easily made so that it can fill huge a huge volume like thousands of cubic meters. Is this even possible? Mercury is too dangerous and scarce...
  4. H

    Example of entropy as function of temperature only

    Hi, I know that changes in entropy can be expressed as a function of temperature, specific volume, and pressure using the fundamental equations of thermodynamics: ds = du/T+pdv/T, where the changes in entropy can be caused by either changing the specific volume or the internal energy. I also...
  5. N

    Which will have a higher temperature?

    Wood and Copper are heated upto a steady state condition which will have a higher average of temperature at points ? Please state your mathematical approach 1. Homework Statement Dimensions remain same for both the materials as well as the temperatures both are heated to is the same Homework...
  6. R

    Fin/Extended surface differential equation for temperature

    I'm trying to deduce the differential equation for temperature for a triangular fin: I know that for a rectangular fin, such as: I can do: Energy entering the left: q_x= -kA\frac{dT(x)}{dx} Energy leaving the right: q_{x+dx} = -kA\frac{dT(x)}{dx} - kA\frac{d² T(x)}{dx²}dx Energy lost by...
  7. B

    Reaction rates, temperature, and thermal energy

    Homework Statement Hi there. My question is more for clarification than a homework question. In my studies, I noticed that my MCAT study manual provides problems relating reaction rates and the effect that temperature and thermal energy have on a reaction. For example, a question asks: in an...
  8. P

    Resistance Temperature Detectors

    Can someone explain three wire and four wire RTD circuits in terms of how the lead resistances affect the voltage output ##V_o = \frac{R_3 V_s}{R_2 + R_3} - \frac{R_4 V_s}{R_1 + R_4}## Also, in the case of a three wire, what is the purpose of Lead C?
  9. avito009

    How does temperature affect viscosity of a liquid?

    I know that When there is increase in temperature the molecules in a viscious liquid move further apart and this decreases the viscosity of the fluid. So does that mean the molecules are far apart in case of liquid and these molecules move further apart with increase in temperature. So a...
  10. A

    The yield strength at temperature SA-789/SA-789 М

    Hi! Could you help me to find the yield strength at temperature SA-789/SA-789 М.
  11. N

    Temperature distribution with heat generation

    hey i really need help with solving this question. 1. Homework Statement the problem is in one dimention x ( 2 plates with diffrent K joined together) for x=0 T=500 ( constat temp) 0<x<L - electric wire is generating heat that maintane the constant temp in x=0 ,it has K=40W/mK. L<x<2L - there...
  12. G

    Does turning a spoon in water raises the temperature?

    Homework Statement I read about Joule's experiment proving the transformation of mechanical work into heat. But say I have a bowl with some water, and I start turning a spoon in it very fast, thus doing work - the water won't get hotter! What am I missing? Homework Equations conservation of...
  13. R

    Auto ignition temperature in pure O2

    First of all (and I know this is not the place I'm supposed to introduce myself,) I'd like to say hi to the forums. Now onto my question. For the past few weeks, I've been thinking about an idea I had. That idea was to use pure oxygen to oxidize a combustion reaction in an engine. I'm sure...
  14. Q

    Temperature dependence of relaxation time T1 vs T2

    Hi, when we assume a obejct with increasing dynamics with increasing temperature, the longitudinal relaxation time T1 should decrease. Since we have, let's say at a frequency 100 MHz , more fluctuations of B0. Ok, then the transversal relaxation time T2 must increase with increasing...
  15. jdawg

    Min power needed to maintain a sample at given temperature

    Homework Statement A sample in a lab is maintained at a cryogenic temperature of -195 °F. The lab is a balmy 70 °F. Heat leaks into the sample at a known rate, Q leak, which raises the temperature. Provide a brief explanation of how you would determine the minimum power needed to maintain the...
  16. B

    What is the Final Temperature of the Mixture?

    Homework Statement Assuming no heat loss to the container or the environment, what is the final temperature (K) of a mixture of 9.28L of liquid 1 (density=1070kg/L & specific heat capacity of 4358J/kg/K) at 378K and 12.15L of a second liquid (density=1070kg/L & specific heat capacity of...
  17. S

    Comparing Q=mc(T-t) and E=sigmaT^4 for Calculating Temperature Change in a Body

    I know two formulas which is to do with change in temperature,first one is : Q=mc(T-t) and the second one is E=sigmaT^4. My question is the difference between these two and where we have to use either of these?
  18. E

    Question regarding temperature of a star and its solar system/planets

    Homework Statement a) The peak intensity of light from the Sun occurs at a wavelength of 500 nm. Astronomers discover a nearby star, “Nus”, which is the same size and mass as the Sun, but has a peak wavelength of half this value. Is Nus hotter or colder than the Sun and by how much? Nus is...
  19. E

    Physics peak wavelength and temperature

    Homework Statement The peak intensity of light from the sun occurs at a wavelength 500nm. Astronomers discover a nearby star X which is the same size and mass as the sun, but has a peak wavelength of half this value. Is X hotter or colder than the sun and by how much?[/B]Homework Equations...
  20. B

    Thermal coefficients of expansion

    Homework Statement A brass rod (linear expansion coef 19*10-6/°C) has a radius of 8139 cm and a copper (linear expansion coef 17*10-6/°C) sheet has a hole or radius 8139+8.86cm. What temperature change (K) is required to close the gap? Homework Equations ΔL/Lo = αΔT? The Attempt at a Solution...
  21. N

    How can you figure out the temperature of electricity?

    I have asked multiple electricians this very question and none of them had an answer. I am working on a project right now that hinges on the control of electrical temperature. This is my first post, thank you in advance.
  22. E

    Compression due to temperature rise vs volume reduction

    If I have 2 sealed tanks A and B of 1 cu ft volume that contain air at atmospheric pressure and are at 300 deg K. temp absolute. For tank A I raise the temperature from 300K to 600K and I suppose the pressure will double due to this and would be 14.7 * 2 = 29.4psi absolute For tank B I use a...
  23. T

    Ice in water question - what is final temperature?

    Homework Statement An ice cube melts in a 10oC glass of water (mass of water is 225g). If the ice is allowed to melt completely, what will the final temperature of the water be? (we're told that the mass of ice can be ignored) Ti = 10oC Latent heat of fusion = Lf = 334000 J/kg specific heat...
  24. V

    Neutron star warm matter - temperature?

    In calculations of quantities in Neutron stars with degenerate matter is usual to set temperature zero. If I'm right it means that pressure of this matter is negligible against pressure due to Pauli principle. But what about situation when the matter is in neutron star locally compressed. How...
  25. P

    Estimating power required to get heat exchanger up to temperature

    Hi, I am working on a fuel delivery system with multiple heat exchangers, piping, etc. I am trying to determine how much power I will need to heat up the gas in the system at the inlet so that all of the components of my system will reach the operating temperatures. For example, I am looking at...
  26. vetgirl1990

    Equilibrium temperature of three different substances

    I've been asked to find the final temperature of different in an insulated container. A combination of 0.25kg water at 20C, 0.4kg aluminum at 26C, and 0.1kg copper at 100C are combined, and allowed to come to thermal equilibrium. Finding the equilibrium temperature for two substances is...
  27. 1

    Why the wire burns in short current with flow of current?

    In short circuit it is said that there is no resistance. So the current produce heat and wire is burnt. But as the rise in temperature increase the resistance then in short circuit heat must rise the resistance. How can we say there is no resistance in short circuit?
  28. E

    Calculating Luminosity and Temperature of the Sun from Pluto

    Hey all, I think that I'm doing this problem correctly but I'm getting an answer that's a couple thousand Kelvins off. Sorry if I should have posted this in the "advanced" section. 1. Homework Statement Part of a flat region of Pluto has the Sun directly overhead. Its surface temperature is 58...
  29. W

    Power and rate of photon emission with a given temperature

    Assuming that your surface temperature is 99.1 F and that you are an ideal blackbody radiator (you are close), find (a) the wavelength at which your spectral radiancy is maximum,(b) the power at which you emit thermal radiation in a wavelength range of 1.0 nm at that wavelength, from a surface...
  30. T

    Heat transfer through finite temperature difference

    Hello, Heat transfer through finite temperature difference is known a irreversible process because heat cannot be transferred from cold to hot temperature without doing any additional work. But, how this transfer affect the efficiency of the system? How this heat transfer decrease the amount of...
  31. S

    What would happen if an object of 689 degrees was in a room

    I was just thinking, If suddenly an object goes about 689 degrees Fahrenheit (365 degrees celsius) in a room, about which perimeter would human life be impossible ?
  32. B

    High Temperature electrochemical measurements

    Hi all, I'm interested in high temperature sample holders of electrochemical measurements especially for Li-ion batteries. But I couldn't find one. Does anyone use it before? Best regards
  33. J

    Equilibrium temperature with 2 states of matter

    35g of h2o(g) at 380K flows into 300g of h2o(l) at 300K. Cp(l)=4.18kJ/K*kg and ΔH(condensation)= -2257kJ/kg. I need to calculate the final temperature when the system reaches equilibrium. Is the heat capacity for the h2o gas different than h2o liquid? Can you calculate heat capacity using...
  34. H

    Pair instability supernova pressure and temperature question

    I read a scientific journal article that discusses pair instability supernova - I am puzzled about something discussed in the article. If the collision of atomic nuclei and energetic gamma rays produces electron and positron pairs which reduces the pressure inside a supermassive star's core -...
  35. yousaf nasir

    What type of pressure and temperature sensors should I use?

    hello. My FYP is to observe the behavior of a valveless pulse jet by changing shape and dimensions of combustion chamber( i am keeping the volume of combustion chamber constant). i need to know what type of sensor should i use for temperature and pressure measurement. I mean temperature should...
  36. Charles CL

    Exit temperature of cooling pond

    Dear All, Referring to the subject above, I have found the calculation of heat load based on [Lawrence,K.W., Norman, C. P. & Yung, T. H. (2005). Advanced Air and Noise Pollution Control. Totowa: Humana Press.] My cooling pond system: 1. Purpose: cooling POME temperature from 70 to 40 degree C...
  37. H

    How to find equilibrium temperature of a system

    Homework Statement A gas is in an insulated box, which is divided into two portions by an insulated partition. There are n1 moles of the gas at temperature T1 in volume V1, and likewise n2 moles of the (same) gas at temperature T2 in volume V2. The partition is composed of two layers; one...
  38. I

    Decrease in temperature and pressure of closed container

    Homework Statement Helium is stored in a tank initially at temperature To and pressure Po. It starts coming out through an opening (pipe outlet) at a constant mass flow rate of mdot. Calculate the decrease in temperature and pressure of the tank (assuming no heat loss to the surroundings) as a...
  39. R

    High temperature spiral sleeves

    Hi. I want use high temperature spiral sleeves which should withstand around 300 deg C and I want wrap these sleeves around power cables which are passed in enclosure having thermal block and we will heat this block up to 400 deg C Please suggest me how to overcome and suggest best suitable...
  40. D

    Dimensional Analysis? Involving Temperature

    I was trying to convert a quantity in BTU/(ft*hr*F) to W/(m*C) and I can do it just fine by using a conversion factor from a table online, but what I want to know is how to come up with that conversion factor. The conversion factor I looked up and have been using is 1 BTU/(ft*hr*F) = 1.73...
  41. jeremyskate

    Thermodynamics resistance temperature scale

    Homework Statement IMPORTANT:There is an error in the statement.α and β are in C not K 2. Homework Equations R=Ro(1 +αt+βt2) The Attempt at a Solution I really don't know what to do because if I isolate t in the equation it will give me the temperature on the ideal gas scale whereas the...
  42. Chrono G. Xay

    Tension (and Frequency) with Change in Temperature

    At one point I had been trying to construct an equation which would calculate the tension on a tuned string with a change in temperature (and therefore the fundamental frequency), but found my calculations were wrong. By extension, the purpose of the project was to be able to calculate what...
  43. Paulene Gueco

    Change in temperature determine the viscosity of honey

    Have you ever tried to eat honey that has been in the refrigerator - hopeless huh? Both the viscosity and the density of honey change with temperature and water content and I'm told the viscosity and temperature follow a inverse cube relationship. Honey is mostly sugar (glucose/fructose and...
  44. J

    How to calculate surface temperature of earth?

    Assumption: Earth is a perfect blackbody. This means that the emissivity (ε) is 1. Earth’s radius = 6371 km Incident solar radiation = 1367 W/m2 Temperature in space = 0 K I'm given the above data. I tried using the E= σεTe4 but that doesn't include the radius of the Earth :S Im really...
  45. Mnemonic

    Thermodynamics relating to temperature and phase changes V.2

    Homework Statement Suppose a room with 75 m3 of air also contains 80 kg of glycerol and the initial temperature in the morning is 16 °C. If 1.2 kWh of heat is added to the room between morning and afternoon, calculate the final temperature of the air in the room in the afternoon. Use 18 °C for...
  46. Mnemonic

    Thermodynamics relating to temperature and phase changes

    Homework Statement Suppose a room with 75 m3 of air also contains 80 kg of glycerol and the initial temperature in the morning is 16 °C. If 1.2 kWh of heat is added to the room between morning and afternoon, calculate the final temperature of the air in the room in the afternoon. Use 18 °C for...
  47. dykuma

    Mass, Temperature, and Relativity?

    By how much (in picograms) does the mass of 1 mol of water at 0° c differ from the mass of 1 mol of ice at 0° c? 1 mol of water = (assuming) 1 mol of ice = 18 g = 1.8E13 pg So, is this a trick question? The logic of a trickster would tell you that there would be no difference, if one assumes...
  48. Pouyan

    Final temperature of ice mixed with water

    What will be the final temperature of 3.00 kg of crushed ice with temperature -3.0 C mixed with 4 liters of water with temperature 10.0 C? We can ignore all the energy exchange with the environment What I do know and I do: the weight of the ice = 3 kg Ice temprature = -3 C melting energy = 3...
  49. Rectifier

    Nitrogen in a cylinder - temperature, work and volume

    This problem was translated from Swedish, sorry for any grammatical errors. The problem A cylinder with nitrogen gas inside is closed by a tight piston (that can slide without friction against the walls of the cylinder). The piston weighs ##s=12.5 kg## and holds the ##m=28## grams of nitrogen...
  50. C

    Standard Temperature Notation for Phase Change

    °Thought just occurred to me.. Is there a standard way of referring to temperature either of a phase change? For example if I write.. "1kg of water is cooled from 20°C to 0°C, how much energy was removed?" ...then potentially two answers might be considered correct depending if you include...
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