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Does close systems really exist?

  1. Jun 16, 2011 #1
    can anyone give me an example of isolated closed system?,bcoz for me there is nothing called closed system,all we can make out is to reduce the temperature of a system to such a critical point that there's hardly any interaction/exchange of energy b/w system and enviroment
     
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  3. Jun 16, 2011 #2

    Hootenanny

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    Depends whether you mean a closed system, or an isolated system. One can find many examples of the former, but there are no known examples of the latter.
     
  4. Jun 16, 2011 #3

    arildno

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    well, if the typical magnitude of internal changees over the time interval we are observing are much greater than the magnitude of what is lost/gained at the boundaries, the observed system can be regarded as roughly closed during the time interval of our observation.
     
  5. Jun 16, 2011 #4
    i don't need a rough approximation ,can u give an example of any closed system ?
     
  6. Jun 16, 2011 #5
    give examples of former but with the reason signifying it's name as "closed"
     
  7. Jun 16, 2011 #6

    Hootenanny

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    Why do you want examples? It is more important to understand the difference between "closed" and "isolated" systems.

    A closed system is one in which mass is conserved and cannot be transfered across the boundary. An isolated system is one in which both mass and energy cannot be transferred accross the boundary.
     
  8. Jun 17, 2011 #7
    if u know the difference u could also give me an example
     
  9. Jun 17, 2011 #8

    Hootenanny

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    I could, but I suspect that this is a homework question and I do not want to do your homework for you.

    How about this: You have a think about the definitions I gave above and try to come up with some examples. I will then tell you if they're right or wrong.
     
  10. Jun 17, 2011 #9
    firstly ,it's not my homework question,i never do my homework
    secondly....i asked for the example bcoz i don't think there a system(closed) that could go from order to disorder without interacting with it's surroundings
     
  11. Jun 20, 2011 #10

    Hootenanny

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    Er...okay.
    And this is why is it vitally important to undertsand the difference between a closed system and an isolated system. A closed system doesn't exchange mass with its surroundings, but that doesn't mean it doesn't interact with its surroundings! Consider the following example. I have a sealed box with a deck of cards neatly stacked in the centre. I now shake the box so that the cards scatter inside the box. No mass has been exchanged between the box and its surroundings, but the system is now in a more disordered state that it was initially.

    Notice that the second law of thermodynamics refers to an isolated system, rather than a closed system.
     
    Last edited: Jun 20, 2011
  12. Jun 20, 2011 #11
    the order of disorder however depends upon the way in which the box is shaken,so the system undergoes interaction,thus system is not isolated....
    i am not sure for this"does second law of thermodynamics require that a system should be left onto itself?"
    or
    second law of thermodynamics is applicable only to those systems which are left onto themselves ?
     
  13. Jun 20, 2011 #12
    He never said it was isolated. he said it was closed.
     
  14. Jun 20, 2011 #13

    Dale

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    There are lots of examples of closed systems:
    A sealed mylar balloon
    A piston when the valves are closed
    A sealed soda can
    A light bulb
    Basically anything that is impermeable and physically closed is thermodynamically closed.
     
  15. Jun 21, 2011 #14
    i am not sure for this"does second law of thermodynamics require that a system should be left onto itself?"
    or
    second law of thermodynamics is applicable only to those systems which are left onto themselves ?
     
  16. Jun 21, 2011 #15

    Hootenanny

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    I'm afraid that I don't understand.
     
  17. Jun 21, 2011 #16
    there is no ideal closed system but wool or cotton can be nearer to perfect closed system
     
  18. Jun 21, 2011 #17

    Hootenanny

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    There certainly are many, many examples of real physical closed systems. I suggest that you see my previous posts regarding isolated vs. closed systems.
     
  19. Jun 21, 2011 #18

    Dale

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    And my post with several examples of closed systems. They are all over the place. There is no doubt that not only do closed systems exist, they are actually quite common.
     
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