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. G

    How much does air volume change with temperature?

    If I have a closed cylinder with a fixed air volume inside and a piston on the open end I need to calculate how much the piston will move as the temperature changes through a range of 100 degrees F? Air volume vs temperature?
  2. G

    Heat required to increase the temperature

    Homework Statement [/B] At high temperatures the nitrogen molecule behaves like a one-dimensional harmonic oscillator. In this situation, estimate how much heat must be added to the system in order to increase the temperature of 1 mole of nitrogen gas by 10 degrees Celsius (for constant volume...
  3. C

    How long does it take for the temperature on Earth to....

    How long does it take for the temperature on Earth to cool down after the sun has set? I want to know if the total solar eclipse will change the temperature.
  4. N

    Experiment - Flux, Irradiance, wavelength from Temperature

    In my experimental setup I have a purpose built small aluminium tube that has a black layer on the inside to mimic a blackbody. The tube is heated so the inside emits as a blackbody. A separate temperature sensor attached to the tube gives the temperature of the tube. I have a thermopile...
  5. N

    Wavelengths, Flux Density, Irradiance from a temperature measurement

    Homework Statement In my experimental setup I have a purpose built small aluminium tube that has a black layer on the inside to mimic a blackbody. The tube is heated so the inside emits as a blackbody. A separate temperature sensor attached to the tube gives the temperature of the tube. I...
  6. H Psi equal E Psi

    In which temperature range does WF_6 melt?

    Hi Everyone I'm studying material Engineering and I'm currently preparing chemistry for the summer exams. Now, there is an old exam question which I don't know how to solve: "In which temperature range does ##[W^{+VI}F_{6}^{-I}]## melt?" My solution: Well, the 18-Electron rule is not...
  7. Anachronist

    Water flow from pressurized tank - versus temperature

    Bernoulli's equation gives us this as the flow rate from a pressurized tank: $$v = C_v \sqrt{2gh + \frac{p}{\rho}}$$ where ##C_v## is the velocity coefficient, ##g## is the acceleration due to gravity, ##h## is the height of the water above the exit hole, ##p## is the excess pressure above...
  8. M

    Solids with different sound velocity at diffrent tempratures

    i work on phononic crystals and i want to find solids with diffrent sound velocities and mass density in diffrent temprature i can just find BST but i need more matherials please help me my friends best regards
  9. Kevin McHugh

    Satellite temperature data vs ground based data

    I've read in the popular media that there is a difference between the two. Is this true, and if so, why?
  10. D

    Temperature related to Current flow on BBr or cables

    Temperature with hot spot by Ir thermal cameras of modern development is being used for measuring on the object of terminal surfaces and cable working temperatures in particular working loads. However, so far no measurements has been designed to obtain the result on the flow of current...
  11. B

    Solving equation with T2 (Final Temperature)

    Hello there, I want to know, what is the equation formula for "Final Temperature" with Temperature Coefficient of Resistance? Let I show you the question as below: The resistance of a component at 0°C is 55Ω and increases to 61Ω when subjected to a rise in temperature. Calculate the change in...
  12. J

    Brightness temperature in remote sensing

    Hi all, I don't know if I'm on the right forum to ask this, but maybe somebody knows anything about brightness temperatures measured by remote sensing devices. In a paper that I read "Atmospheric corrections for retrieving ground brightness temperature at commonly-used passive microwave...
  13. jk22

    B Temperature & Relativity: Can Plasma Fusion Test Limits?

    Do we know if experiments with plasma fusion could test relativity and its speed limit because of the maximal speed ? Like $$3/2kT=1/2mc^2$$ hence for example with hydrogen the maximal temperature should be around $$10^{12}K $$. I read that they achieved 8*10^7 in wendelstein. Or should it be...
  14. M

    Viscosity and temperature, density is changing....

    Homework Statement Hi, I am doing physics lab on finding coefficient viscosity of fluids and how it changes by temperature by dropping a marble into fluids, finding terminal velocity, then using stoke's law to find viscosity. (using density of fluid, sphere, sphere diameter etc). The equation...
  15. K

    (thermo) how to calculate the temperature of a coal furnace (applied)

    I am an new EE with my FE, but my thermo knowledge is lacking in many areas. Its one area where i would like to become an expert. So i try to find ways of applying thermo analysis on my free time to imprve my skills. where here is one and I have no idea where to even start. a youtuber with a...
  16. bruha

    I Why Do Stars and Hot Metal Show Different Colors at Similar Temperatures?

    Hello I am interested about correlation between star surface temperature and its visioned colour ,for example orange red Arctur has surf temperature cca 4300 K ..but comparing to for example hot piece of metal? its temperature 2000 K respond white colour. ? What is a matter of this disagreemet...
  17. J

    Temperature change (first law of thermodynamics)

    Hi, From the first law of thermodynamics it follows: Cp * (δT/δt) = (δQ/δt) where Cp = specific heat capacity, T = temperature, Q = heat, t = time From this formula, you would derive that temperature keeps on increasing as long as dQ/dt > 0. But if you, for example, look at the idealized...
  18. N

    Steam Condenser Not Working: Pressure & Temperature Issues

    The condensate drain from a steam condenser is expected to be about 50 deg C. It's only 38 deg C or so. There's a mix of steam and non condensable gases coming into the condenser. Its pressure seems slightly higher, being about 0.25 bar abs instead of 0.2 bar. What does it indicate? Also, no...
  19. E

    Calculating the mass of water from Temperature and Heat Added

    Homework Statement Find the mass of water in this container when given a data plot of temperature (C) and Heat Added (kJ) I have NO idea where to even start with this.
  20. BTEC Michio Kaku

    GCSE Physics : Temperature & Gravitational potential energy

    Homework Statement Q7. Some lead shot with a mass of 50 grams is placed into a card board box the distance from one end to the other being 1m. The ends are sealed with rubber bungs in order to prevent the lead shots from falling out, the tube is rotated so the lead shots fall down from one end...
  21. PHstud

    Liquid to gas expansion temperature change in a tank

    Hello ! I have troube doing a calculation. Let's say we have a volume Vi in a tank at a pressure Pi. If I let my tank open, the tank's liquid will start to boil to keep the pressure Pi inside the tank. Now, at the end, I will have a volume Vf in the tank, and still a pressure Pi. But the...
  22. oversight

    How do I measure the temperature of my infrared sauna?

    Sooooo... I have a Far infrared (FIR) sauna. It has large flat 'carbon' panel heaters. They get warm to the touch and won't burn you if you touch them. My non contact infrared thermometer zapper says that they get to about 70 degrees C. They are meant to be producing lots of FIR. A regular...
  23. J

    Making a temperature controlled heating element

    I'm considering making a plastic melter / extruder for making my own 3D printer filament as opposed to buying the spools of it. The basics of the project are simple, but the hard part (for me at least) is making a heating element that has a control on it so that I can turn the heat up or down...
  24. T

    Temperature Conversions: Understanding the Use of Conversion Factors for Rates

    Why is that whenever we convert a temperature, say ##^\circ C## to ##^\circ F##, we use ##T_F = \frac{9}{5}T_C+32##, but whenever it involves a rate, say ##^\circ C/m##, we only multiply by the slope of the previously given formula? I would say it's because of the latter being a rate so...
  25. J

    Would this device(pic inside) work for boiling cold water?

    Imagine some giant glass(or other material) dome placed on top of some ocean or lake. Then pump some air out of this dome, until the water level rises a few meters under the dome. Place another dome below the first dome, and repeat the process, resulting in a little less pressure in the second...
  26. satyadangin

    How to design canal to reduce stream temperature?

    If i have atm temperature around 32 deg Celsius, volumetric flow 6000m3/h, fluid temperature inlet 47 deg Celcius. How to get minimum possible dimension for my canal if its maximum possible length is 180 m and fluid temperature outlet at least 40 deg Celcius?
  27. A

    Temperature on the outer surface of insulation

    This seems basic, but I'm stuck. Look at the attached picture. I'm trying to find the temperature on the outer surface of the insulation. Is it not possible because I do not know the rate of heat transfer? How do pipe designers know the required thickness of insulation needed to reduce to a...
  28. B

    I Humidity when T is not constant in space

    Hi all! How is humidity related to temperature in a system where temperature is constant in time but not in space? As an example: If we have humid air trapped between two parallel walls with T1 and T2 respectively, how does humidity behave along the line from one to the other wall? Is absolute...
  29. S

    A Critical temperature for bubble nucleation

    Consider that the criterion for bubble nucleation (in a field theory) is the following: $$\exp(-S_{3}/T) \gtrsim \frac{3}{4\pi} \left(\frac{H}{T}\right)^{4} \left(\frac{2\pi T}{S_{3}}\right)^{3/2},$$ where ##S_3## is the three-dimensional action of the theory and ##H## is the Hubble scale. 1...
  30. Anachronist

    Pressure and temperature of expanding humid air

    As a follow-on to this thread, which in turn followed this closed thread, I'm starting a new thread on a related real-world problem. Say I have a 2-liter plastic soda bottle filled partway with water, and pressurized. It has been sitting inverted (with the opening pointed down, and sealed) for...
  31. eigenmax

    Calculation of temperature of a current-carrying wire

    Hello, I'm working on an electron gun and I am wondering if there is a way to calculate the temperature of the hot cathode, from it's thickness, resistance, the amount of current running through it, or other relevant factors. This is part of an attempt to calculate the energy of the emittted...
  32. T

    Why Are Refrigerators More Complex Than Stoves?

    Why is it so much easier to increase the temperature of something than it is to decrease the temperature? Why are refrigerators more complex than stoves?
  33. R

    Partition function for ideal gas for "medium" temperature

    Looking for the heat capacity of ideal gas due to rotational degrees of freedom. If the temperature of the gas is much higher than the temperature corresponding to the energy differential between states,the partition function can be written as the integral over the density of states. If the...
  34. C

    Calculate the moisture content of air

    Homework Statement (Simplified) During tests at cliffside power station, the following data was recorded from the cooling tower. A cooling tower has a 9 cell draft design, each diameter is 10m. Data D_o = 10m V_exit = 14.4 m/s T_exit(15 celsius) = 288.15K Ambient conditions : T(15 celsius) =...
  35. Cheesycheese213

    Does temperature change with depth in a fluid?

    Hi, so someone probably has already asked this, but does temperature increase or decrease with depth in a fluid? I thought it would decrease since it has more pressure but it is probably wrong, or doesn't make sense. I was confused because the ocean gets colder the deeper you go, but then does...
  36. S

    Earth Temperature Homework Solution

    Homework Statement Calculate the temperature of the Earth assuming that the Sun and the Earth are black bodies. Assume that Earth is in a steady state as far as energy balance is concerned Homework Equations ##\frac{E}{St} = \sigma T^4## - Stefan-Boltzman law The Attempt at a Solution The...
  37. T

    B What is the origin of the Gibbons-Hawking temperature?

    I recently submitted the following question to Dr. Michio Kaku on his Facebook page regarding an unfamiliar concept in his book "Parallel Universes": Dr. Kaku, In your book "Parallel Universes", pg. 301, you mention something called the Gibbons-Hawking temperature, a theoretical low...
  38. E

    Temperature of a spinning and non spinning asteroid

    Homework Statement Consider a rapidly rotating asteroid with an albedo (reflectivity) averaged over the solar spectrum of 0.05 that orbits around a 3 solar mass star that has the same surface temperature as the Sun. The asteroid’s orbit has a semi-major axis of 15 AU. What is its equilibrium...
  39. G

    Cooling a gas by releasing it into vacuum: Entropy?

    Hi. I just read an article where following cooling method is described. Apparently it's very common, but I don't know what it's called: A gas under pressure is released into a vacuum through a small hole. The average particle speed in this beam of gas is the same as before, but the...
  40. Emmanuel_Euler

    Dielectric Constant Vs Temperature Vs Polarity

    please explain the concept of dielectric constant in the simplest CHEMICAL terms possible. why does it decrease when the temperature increases? and why does it increase when the polarity increases? please keep it simple and brief.
  41. olgkd123

    How does compression cool water in a household water cooler?

    How does compression cool water in a household water cooler? I was reading and it says, " The water inside the water cooler is fed into a reservoir, where it is cooled using a refrigerant. A refrigerant is a cooling medium that is circulated in pipes that are located close to the reservoir in...
  42. D

    Why does stretching a rubber band increase its temperature?

    I was reading the Feynman lectures and in one of the chapters on thermodynamics it is stated that stretching a rubber band makes its temperature rise. I feel like I understand the thermodynamics of the rubber band and yet this statement is puzzling me. I believe that when you stretch a rubber...
  43. A

    Final Temperature of a Lightbulb filament

    Homework Statement When an incandescent light bulb is switched on, it can take a few moments for the filament to fully heat up and reach its equilibrium temperature. Assume the filament of a given light bulb is made of Tungsten, and also assume the potential difference across the filament is...
  44. T

    Effect of Temperature on Chemical Reaction Equilibrium

    here is the question (part I): For part I, I need some assistance, I cannot figure out how to do the question. I know eventually what to do, it's just working out the equilibrium constants I'm having trouble with. So to start, I want to work out the K values at 600K and 800K, I do this by...
  45. S

    A Dependence of entropy and temperature on Planck's constant

    Consider the dependence of entropy and of temperature on the reduced Planck's constant (taken from page 23 of Thomas Hartman's lecture notes(http://www.hartmanhep.net/topics2015/) on Quantum Gravity): $$S \propto \hbar, \qquad \qquad T \propto \hbar.$$ I do not quite see how entropy can depend...
  46. W

    Equipartition ceasing to apply at what temperature?

    Homework Statement A tuning fork has a frequency of 440 Hz. A) What is the size of one quantum of energy of vibration? B) To approximately what temperature would the fork have to be cooled before equipartition would cease to apply to its thermal motions? Homework EquationsThe Attempt at a...
  47. E

    Temperature in a Carnot heat engine

    Homework Statement A Carnot heat engine takes 95 cycles to lift a 10 kg. mass a height of 11 m . The engine exhausts 14 J of heat per cycle to a cold reservoir at 0∘C. What is the temperature of the hot reservoir? Homework Equations η=1-(Tc/Th)=W/Qh The Attempt at a Solution I've tried...
  48. AHMEDbr

    Engineering Temperature compensation circuit

    Homework Statement I am designing a local oscillator ( clapp ) whose frequency needs to be kept constant even with varying temperatures , this oscillator have an output frequency 150 MHZ , and power supply 3.3 V Homework Equations which temperature compensation circuit must be used with this...
  49. Adam Rabe

    Thermodynamics question: temperature between layers

    Homework Statement Homework Equations h = k/d 1/h (total) = 1/h + 1/h + 1/h... + 1/h (surf) Q/t = h A T The Attempt at a Solution For the thermodynamic one i got up to calculating the total heat transfer coeffecient but i don't know where to go from there as its asking for the outside...
  50. R

    Thermodynamics Gas Mixture - Dew Point Temperature

    Homework Statement Only Number 1, not number 2 Homework Equations Dew Point Temperature T = Saturated Temperated at Vapor Pressure Partial Pressure = (mole fraction) x (Mixture Pressure) The Attempt at a Solution The dew point temperature is only dependent on the pressure of the water...
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