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2nd principle of termoDynamics

  1. Dec 14, 2003 #1
    The second principle of termodynamics says:
    cooler object cannot give away heat spontaneously to warmer one.
    I wonder then how do cooler and wormer object appear in a closed system after they have equalized their heat.Or in other words:
    Is there a way back <=> Could this phenomenon be reversible in a closed system?

    Billioners don't appear in the middle of desert but in the center of society.
     
  2. jcsd
  3. Dec 14, 2003 #2

    russ_watters

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    I'm not sure I understand what you are asking, but heat always flows from areas of higher temp to areas of lower temp. It is not reversible (not even a heat pump qualifies as reversing it).
     
  4. Dec 15, 2003 #3
    I think I get it. He's asking how the second law can be true given that hot and cold things can spontanteously appear. The answer is compound:
    1. the second law is statistical, there can be really small variations
    2. It only holds for closed systems, but there are technically no closed systems, unless one has the whole universe be your system
    3. You might be getting confused with you experience of the world. If you have a piece of metal sitting in a room at room temperature, and touch it, it will feel cold. This is because you are warmer than it and it conducts heat faster than the air, so it draws away your heat faster than the air does, cooling that area slightly below the usual cooling caused by the air, and makes itself warmer.
    So pretty much, it is rare and unnoticable that hot and cold things spontaneously occur, so the second law is a really really good rule of thumb.
     
    Last edited: Dec 15, 2003
  5. Dec 16, 2003 #4
    I was aiming more on this:
    I have isolated one termo system with cold and warm objects in it.
    I brought them in direct contact.
    The warm object is giving it's heat to the cool until they become equally warm.
    The system preserves all it's heat.
    Now if I want to differentiate/distinguish them again I have to insert some 3rd object from outside into the system.
    But this will not open the system or it won't break it's isolation cause how much heat the 3rd object is getting from the 1st one that much heat is giving to the 2nd.
    In the end my intention is to close the circuit or to get where I started.
    Unfortunatelly, this TD principle won't let me do so cause:
    The 3rd object has same heat as for the 1st as for the 2nd object which means it will (according to this TD principle) equally worp up(cool down) both objects.
    It's same as polarization and neutralization.

    How do I polarize the object's heats again without opening the system?
     
  6. Dec 16, 2003 #5

    russ_watters

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    Insulation?
     
  7. Dec 16, 2003 #6
    This can slow the process (I know you know this Russ, but this is for the original poster) but there is no perfect insulator, so eventually the temperatures will again equalize.
     
  8. Dec 16, 2003 #7
    If I am understanding your question correctly, you are placing two objects with significant temperature differences(hot and cold) into an insulated container. Then, you bring those two objects together, physically or environmentally, to effect a heat transfer from the hot object to the cold object, eventually equalizing an average temperature of both.
    Then, if I understand this, your goal is to separate the objects again, with each object having their original temperature differances.
    Can this be done in an isolated system? Of course! Very easily.
    Can this be done without the introduction of additional energy? No.
     
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