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. PGaccount

    I Exploring the Origin of Unruh Temperature: Theories and Implications

    A uniformly accelerating observer registers a temperature T = 1/2π Or an observer hovering near a black hole. According to current understanding, what are the best ideas about the origin of this temperature?
  2. TachyonLord

    Resistance of Platinum decreases with an increase in temperature ?

    Basic Procedure The experiment basically involves finding the null point on the Carey Foster's bridge with the PRT as the unknown resistance and using a Resistance box as the variable resistance. In the above diagram, P and Q are 2 fixed resistors of equal resistances. For obtaining the first...
  3. gdritz

    Molten metal temperature vs Induction Coil Current

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  4. piyush_1903

    Exploring Frequency & Temperature: Theory & Experiment

    So, my apparatus consists of a basic wooden plank with a nail on one end and a guitar tuner on the other. I plan on using a heating lamp to control the temperature of the apparatus, which is placed inside an insulation box, and use a non-contact infrared thermometer to measure the temperature of...
  5. men5j2s

    Temperature of a compressed gas

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  6. H

    Is it possible to calculate an incandescent bulb's temperature from V?

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  7. granzer

    Why doesn't the stagnation temperature change in a stator?

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  8. fsonnichsen

    Precision Temperature Measurement

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  9. S

    How to calculate the transition temperature in this problem?

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  10. Baibhab Bose

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  11. H

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  12. L

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  13. A

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  14. S

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  15. electr0dave

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  16. fernelau

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  17. L

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  18. andrea1313

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  19. S

    Misc. How Can I Best Insulate a Safe to Protect Heat-Sensitive Materials?

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  20. J

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  21. J

    I How Do You Calculate Initial Pressure and Final Volume in Adiabatic Expansion?

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  22. Nikhil Rajagopalan

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  23. AttoBlaze

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  24. wishstar

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  25. Brendan Webb

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  28. W

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  29. R

    B Understanding Color & Temperature

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  30. D

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  31. K

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  32. D

    Thermodynamic possiblity for outlet temperatures of heat exchanger

    I have a heat & mass balance diagram wherein there is a shell and tube heat exchanger to recover heat from hot exhaust gas using cold water. The exhaust gas inlet temperature is 120°C and the outlet is at 40°C. The inlet water temperature is 35°C while the outlet water temperature is at 50°C...
  33. D

    What is the relationship between pipes and temperature?

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  34. J

    Understanding a simple statement regarding the measurement of temperature

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  35. C

    Decompression of dry air in relation to temperature

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  36. J

    Find the equilibrium temperature & the amount of ice/water

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  37. A

    Given RMS Speed, Find Temperature

    mass of N2 = 28 * 1.67e-27 kg not sure if this is the right one - just googled it triple covalent bond N2 radii = 54e-12 m I tried to first find the rms speed: v = x/t = 50 * 54e-12 / 3 m/s Then I solved for T (in K): [50 * 54e-12 / 3]^2 * [28 * 1.67e-27] / [3 * 1.38e-23] = 9.14e-22 K
  38. PCal

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    This is the final question on my assignment and I'm clueless as to where I should even start as the lesson seems to give no guidance. Help would be massively appreciated!
  39. C

    For a throttling valve, why is it that temperature remains the same?

    For a throttling valve C.V analysis, I am wondering why is it known that temperature remains the same for ideal gases. I understand that using the energy balance equation, I end up with h1=h2. Pretty simple so far. By breaking down enthalpy into its components u1+P1v1 = u2+P2v2 I realized that...
  40. thebosonbreaker

    What temperature should be used for the Friedel-Crafts alkylation of benzene?

    Hello, My sources seem to contradict here - one claims that it should be carried out at room temperature, while the other suggests that heating under reflux is necessary. Could someone please clarify this for me? Many thanks.
  41. Molloy

    Thermosphere temperature paradox?

    This quote from Wikipedia says that temperatures in the Thermosphere can reach 2,500 C during the daytime but "despite the high temperature, an observer or object will experience cold temperatures". "The highly diluted gas in this layer can reach 2,500 °C (4,530 °F) during the day. Despite the...
  42. dRic2

    Resonance escape probability after a change in temperature

    Hi, I'm reading Lamarsh's book "Introduction to nuclear reactor theory" and in chapter 7 he discusses the influence of temperature on the resonance escape probability. He states that after an increase in Temperature, as a consequence of Doppler broadening, the microscopic absorption cross...
  43. T

    B Temperature regulation in Earth orbit

    If I had an object in an orbit around the Earth that I kept continually shaded from the sun, how cold would it get? Assuming the shade device was not physically connected to and was sufficiently far away from the object to not radiate any heat to it. And if I actively adjusted how much shade...
  44. Abimotek

    Automotive Honda EU generator -- which is the best oil temperature range rating?

    Please below attached which is best oil in my 4 stroke gen set Honda EU 10i, weather temperature attached in my area. I all so have two oil grades > 4T 10w-30 and Coastal Synthetic Blend 5W-30, please advice which will help the life of the gen set
  45. P

    How do we calculate the temperature of a laser-heated substance?

    P_b/P_a =0.4 I have calculated mass of the syrup which is 0.42g We know that the power of a laser before is 100mW and after is 40mW, that means that the energy absorbed by the syrup is equal to 0.6J/s. I'm not really sure what to do here, the substance through which laser is going is Maple...
  46. ChrisXenon

    Temperature and molecular Kinetic Energy

    We are told that temperature measures the average kinetic energy of the molecules or atoms in a substance, but this cannot be true. If I take a jar of water and put the jar in my car and drive it aorund, it won't get hotter, though it's kinetic energy must surely be higher. Clearly, I've got...
  47. C

    Why is air in atmospheric pressure and room temperature a gas?

    This seems like a simple thermodynamics question but I would like clarification. So the absolute critical temperature is 132.5 K (-221.17 F) and the absolute critical pressure is 3.77Mpa (546.7 psi). I understand that for temperatures above the critical point, a pure substance undergoes an...
  48. Magellanic

    Thermo: Calculating the temperature drop from gas leaving a system

    Hi PF! I have a tricky problem that I'm trying to model, and none of the typical textbook examples cover this--or they only cover it tangentially--so I was hoping to get some insight here. (Couldn't find a "Thermodynamics" section of the forums so if there's a better place to post this, please...
  49. Q

    High temperature electrical insolator that repels carbon deposits

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  50. C

    Does temperature increase when water is boiling at 100C......

    Does temperature increase when water is boiling at 100C in a closed system? I am picturing a scenario where I am boiling water in a pot to make pasta. However, I decide to close the pot as the water is still boiling. By doing this I am sealing away the system of study from the environment. Thus...
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