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How does heat transfer take place?

  1. Mar 21, 2015 #1
    I'm having a problem with understanding how energy flows from one body to the other.

    So gases at high pressure travel towards low pressured areas. So there is a reason behind this. Since molecules of gases have the tendancy to move away from each other, they travel towards low pressured areas. So molecules are the paticles that comprise all the matter.
    So what is heat energy comprised of? Are there any particles in it? Why does it travel from a hotter body to a colder body??
     
  2. jcsd
  3. Mar 21, 2015 #2
    Heat energy comes from the speed of those molecules. The more they bump off of each other, the hotter the substance.
     
  4. Mar 21, 2015 #3

    phinds

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    There are three forms of heat transfer: convection, radiation, and conduction. Google them.
     
  5. Mar 21, 2015 #4
    Your answer is what heat is made of and if it comprises of particles?
    I can only say you that it isn't a substance: in past one believed it was a form of matter like fluid but then it was discovered that in a solid object after heat transfer there wasn't an appreciable decrease of mass. Now it is defined as a energy in transfer.
    Kinetic theory explains at a microscopic level how this transfer take place: matter is made of particles like molecules which get this energy; the disordered motion of the molecules in gases or their vibrations in solids , which are due to heat, generates heat exchanges among this particles.
    Another way of transfer, we've seen, is radiation: here the heat is emitted from an emitting surface of a warm body as infrared, an electromagnetic wave, and then it is absorbed by a receiving surface.
     
  6. Mar 21, 2015 #5
    Then what are photons actually??
     
  7. Mar 21, 2015 #6
    Thanks a lot! That was a good explanation. But I came to know that light contains mas less particles called photons. Light is a form of energy, right? Then why doesn't heat energy have those particles?
     
  8. Mar 21, 2015 #7

    phinds

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    You might want to give some thought to what sunlight is.
     
  9. Mar 21, 2015 #8
    I'm nice to help you; but I'm not an expert and so I can't tell you...
     
  10. Mar 21, 2015 #9
    No, you don't have to say that you aren't an expert sir. You helped me a lot, so thank you once again Mr. Pierce610.. :smile::smile::smile:
     
  11. Mar 21, 2015 #10

    phinds

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    Photons are quantum objects. If you measure them for wave properties, they will show wave properties but they are not classical waves. If you measure them for particle properties, they will show particle properties, but they are not classical particles. They are quantum objects. Period.
     
  12. Mar 21, 2015 #11
    a. When a molecule absorbs a photon, it moves faster. That is heating through radiation.
    b. When molecules bump into each other as I dryly stated, that is heating by conduction.
    c. When a moving molecule is brought somewhere else, that is heating by convection.

    When I say "moving", that includes rotation, vibration, and going somewhere else.

    So photons can cause heat, with a. above, but photons "are" not heat. Photons cause heat by causing molecules to move when absorbed.
     
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