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. Jimster41

    Relationship between measurement and temperature

    A system at absolute zero (ground state) can't be be divided into observer and observed, can it? I'm struggling with the relationship between superposition, decoherence and temperature. Decoherence requires information. Information requires energy. Though multiple basis of "information" can...
  2. PytrTchaikovsky

    Thermal Radiation: Calc Total Emitted Joules in Certain Temp Range

    Dear forum I am working with thermal radiation. This is the specific formula: P = σ ⋅ A ⋅ T4 P = emitted effect (W, J/s) σ = Stefan-Boltzmann constant (5,67 ⋅ 10-8) A = area of object (m2) T = temperature of object (K) How can I get to know the...
  3. FarabiBinImran

    Want to Calculate Volume, Given Time, Temperature & Energy

    Hi, I want to calculate volume of a tank , 1. Tank contains water and it leaves tank at 7 degree celcius and comes back at 11 degree celcius. So ∇T= 4°C. 2. Time required to complately empty 20 Minutes 3. Energy absorbed in raise from 7ºC to 11ºC = 25 KW I need to calculate the volume of...
  4. D

    Temperature increase with pressure in an open vessel?

    Hello all, new here please excuse if this is in the wrong area of the forum. My question is does temperature increase in a linear fashion when pressure is added? What formula can be used to accurately monitor temperature increase as pressure is added? Imagine having a set temperature, let's...
  5. K

    Maximum mass of a metal you can melt; Heat of Transformation

    Homework Statement What is the maximum mass of lead you could melt with 2000 J of heat, starting from 25 ∘C ? Lead melts at 328∘C , its specific heat is 128 J/(kg⋅K) , and its heat of fusion is 2.5×10^4 J/kg . Homework Equations Need to find both the mass in the heat of transformation (Q =...
  6. S

    Temperature increase by light absorption

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  7. ugi_89

    Temperature controlling system with peltier battery?

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  8. P

    Detect Airflow + Regulate Temperature

    Heyo, first post here...! Sorry for my English and I will reword anything if it is needed. I've been struggling to solve this for a few days, please help me with some insight or intuition. I have application with a a heating element leading to little ceramic crucible, there is an airflow in and...
  9. skepticwulf

    How Does Room Temperature Affect Air Molecule Energy from Winter to Summer?

    According to KMT, Avarage kinetic energy of 1 mole gas is=(3/2) x R x T So , in winter in my cold room , the gases have Kea=34J/mole (T=5oC) and in summer that figure climbs to, -roughly- 37J/mole, (T=25oC) Difference is , 3J per mole. If my rooms dimensions are 3m x 3m x 4m, volume is 36m^3...
  10. G

    Temperature Tests: Investigating a Surprising Result

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  11. PytrTchaikovsky

    How can the effect of air temperature on an object be quantified?

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  12. A

    Can temperature affect the mass of water

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  13. TESL@

    What causes current decay in plasma collisions?

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  14. Q

    Does weight / inertia / momentum change with temperature?

    I did a simple experiment. I took a small block of copper (40g) and sensitive scales. First I cooled the block in a freezer (-2C) and checked its weight. Then heated it up to 300C in the oven and checked weight again. The difference in weight is well observed (4 - 5mg). Results are consistent...
  15. E

    Pumping Bicycle tire: Find volume, work done, temperature

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  16. marcophys

    Liquid Na2O3Si: what causes solidification at temperature?

    I have a refractory adhesive based upon liquid Na2O3Si and other unknown constituents. It remains a liquid until a specific temperature... when it boils, or gasses. At this point, if the temperature is removed (or increased), the liquid becomes a solid. It would appear (perhaps incorrectly)...
  17. A

    Temperature in Constant volume gas thermometer.

    In the constant volume gas thermometer, T (°c)=[P(T)-P(f)]×100/[P(b)-P(f)] (P(T) means gas pressure at T°c P(b) and P(f) for the water's boiling point and freezing point) Is it right?
  18. F

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  19. HelloCthulhu

    Temperature of gas during water electrolysis

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  20. T

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  21. S

    What Is the Correct Debye Temperature Calculation for Gold?

    Homework Statement Calculate the Debye temperature for gold Homework Equations $$Θ_D = \hbar \frac{v_s}{k_b} \sqrt[3]{6π^2 \frac{N}{V}}$$ Speed of sound in gold: $$v_s=3240 m/s$$ The Attempt at a Solution I used the equation for ΘD and for the concentration I used the value for atom density...
  22. EternusVia

    Data Corruption from Sensors with Long Wires

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  23. D

    Does DOS depend on Temperature?

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  24. A

    Natural ventilation through single opening

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  25. K

    Gas field temperature gauges

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  26. Z

    How Does Uranium Decay Impact the Temperature of Surrounding Lead?

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  27. Z

    Vaporization and Energy absorption

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  28. M

    Compression of pure nitrogen: Calculating power and temperature

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  29. Hyo X

    Temperature coefficient of resistance - size effects vs bulk

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  30. N

    Kinetic energy -- plot molecule frequency vs temperature

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  31. H

    Nichrome Wire Temperature Calculation

    Hey there, I've scouted this forum for years, and it's nice to have finally joined. :) I come to you with a problem. The objective is to find the correct voltage needed to heat air and another metal to a certain temperature, and then to maintain this certain temperature indefinitely within...
  32. HelloCthulhu

    Temperature of water electrolyzed at 5A for 1 min

    Homework Statement 36mL of water undergoes electrolysis at 15A/6V. What is the temperature of the water after 1 min? Homework Equations [/B] 1g = 1mL Coulombs = Amps x seconds Joules = Coulombs x Volt Specific Heat Capacity= The Attempt at a Solution 15A x 60s = 900C 900C x 6V = 5400...
  33. C

    Intro Physics Great introduction to heat, temperature and thermodynamics.

    So i need a introduction to Heat, temperature and thermodynamics; not a very advanced text, just a clear beginner text that can include math/calculus. I'm just curious about how heat was/is measured, how it's defined and how it works.Also I wan't to understand thermodynamics and entropy and how...
  34. ORF

    Absolute Temperature & Entropy: Which is Lorentz Scalar?

    Hello In relativity, what magnitude is absolute*: temperature or entropy? *absolute = equal for all observers (= a Lorentz scalar) Thank you for your time :) Greetings!
  35. P

    Which Color Provides the Best Green House Effect for Pool Solar Covers?

    Hi, I have some thoughts about making a much better pool solar cover. My thoughts are to maximize the temperature increase. I plan to suspend a plastic film 6 inches above the surface of the pool water creating a green house effect. Normally, very small plastic are pockets are embedded in the...
  36. Fluxxx

    Speed of wave with temperature

    Homework Statement A wire is strung tightly between two immovable posts. Decide whether the speed of the transverse wave on this wire would increase, decrease, or remain the same when the temperature increases. Ignore any change in the mass per unit length of the wire. Homework Equations...
  37. I

    Max PSI Before a Certain Temperature is Reached

    Greetings all, this is my first post. I'm attempting to solve a problem regarding different octane fuels for a combustion engine and how pressure from a turbo can influence the Auto Ignition Point (Temperature where a fuel can ignite before reaching its proper cylinder position). The items of...
  38. A

    Formula for relating time and heat gained for closed system

    This is for work. I need to make a table for a client. What we did: had two different closed systems, only difference is material. We had frozen goods in both containers, the containers were both removed from the cooled surroundings they were in and placed outside. The temperatures were...
  39. L

    Sky temperature profiles and black body radiation

    I want to know, excluding the sun with an appropriate boundary, whether it is possible for the balance of bbr to be positive for outerspace rather than on earth? I am thinking of a half convex with an active polariser across-the outer surface which allows through most radiation below the...
  40. P

    Temperature of a gas in a container

    A rectangular (simplified) container with rigid surfaces, has a certain mass of ideal gas within it, and it accelerates in free space, undergoing rectilinear motion. There are no dissipative forces. Now, since the container moves, its kinetic energy increases, and since the temperature of the...
  41. B

    Do rotational degrees of freedom contribute to temperature?

    I cannot find a simple answer to this question anywhere. What degrees of freedom contribute to the temperature of a gas? Let's say we have a box of ideal gas. The temperature is the average kinetic energy of the particles and only includes translational degrees of freedom: velocity. Now...
  42. S

    How Can the Speed of Sound Help Determine Room Temperature?

    Homework Statement Calculate the room temperature by using the speed of sound formula and using the given values. Known Data: Frequency = 480 Hz 2nd Resonant length = 54cm or 0.54m Homework Equations v = 331 + (0.60)T T = (v - 331)/0.60 v = fλ (Open-Closed air column) L = (3/4)λ The...
  43. M

    Energy for heating the air to a specific temperature

    Hi all. I'm trying to find haw much energy is required to get the air heated up to one desire temperature in oven. . I guess the next issue will be haw much energy is required to keep the temperature at the setting point. A theoretic starting point will be useful from your side, if possible...
  44. M

    Gas consumption vs oven temperature setting point

    Haw can I calculate/estimate the potential gas consumption in an industrial oven after the reduction of the temperature setting point?
  45. U

    CMB Temperature - Will hydrogen be ionized?

    Homework Statement Energy density of radiation ##\rho_r = 8 \times 10^{-14} J m^{-3}## and energy density of matter ##\rho_m = 2.63 \times 10^{-10} J m^{-3}##. Baryon density parameter is ##\Omega_b = 0.04##. Temperature of CMB today is ##2.73 K##. Ionization energy of Hydrogen is ##13.6 eV##...
  46. mooncrater

    Reason for: Temperature is proportional to atomic motio

    Yeah... I know many of you people might be laughing but still I don't understand how can we simply reach the conclusion that increasing temperature increases the atomic motion. Consider this : When we push something, it moves (don't over think about this one) when we apply torque on something...
  47. Wheeew

    Exploring Temperature Sensing with BJTs

    Hey there, I want to build a simple temperature sensor using a BJT (BC547, 2N2222, or similar). I'm not sure how should I do that. My first thoughts where: measuring the Vbe, using around 9v to 12v as Vcc, the transistor with common-emitter; then just wrap the transistor in plastic or...
  48. M

    Find the time needed to warm the water to a temperature

    Homework Statement An electrical resistence has a power of 1 kW. It is put inside a container that has 10 liters water. The water is in temperature 20C with pressure 1 atm. Find the time to warm the water to the temperature 120C Homework Equations A=P*t The Attempt at a Solution I thought to...
  49. B

    Minimal film boiling temperature (Core reflooding)

    Hello Forumers and Physics-addicted Fellows! I'm an applied nuclear engineering scientist by profession and thermal physicist by education. well nowadays I'm really involved into the describing the processes in Light Water Reactor core during Emergency Core Cooling System in action. In details...
  50. B

    VSCPT and recoil limit on temperature

    I have read that it is possible to go under recoil temperature limit using VSCPT (Velocity Selective Coherent Population Trapping) and that this method is based on atoms trapping in quantum state in which they can't absorb light. I have found same papers but they are too detailed for my...
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