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Decrease in entropy and 2nd Law of Thermodynamics!

  1. Aug 18, 2010 #1
    General entrpy quesiton from a book- (not a homework quesiton):

    When a room temp object is placed in a refrigerator, heat flows out of object and its entropy decreases. Indeed, the refrigerator may be said to be a device for sucking entopy out of warm objects. How can such a decrease in entropy be consistent with the 2nd law of thermodynamics?

    2nd law of thermodynamics:
    The total entropy of an isolated system cannot decrase, it may increase.
     
  2. jcsd
  3. Aug 18, 2010 #2
    Your refer' is pumping entropy into your kitchen...

    Entropy in a closed system -- one where no energy crosses the boundary between system and not-system -- always increases. While the door of the refrigerator may be closed, it's not a closed system because heat is being transferred from inside to outside via the condenser you'll find someplace on the back.
     
  4. Aug 18, 2010 #3
    The total entropy of an isolated system cannot decrease.

    The fridge is not an isolated system by itself, it gives off heat so your system would (roughly) be the room enclosing the refrigerator. The heat the refrigerator is giving off generates more entropy than the cooling effect of the stuff in the fridge has decreasing entropy. This is because you need to consider the efficiency of the fridge. A fridge is not 100% efficient, nor can it ever be.
     
  5. Aug 19, 2010 #4
    Thank you so much schip666! and Feldoh.

    if you dont mind me asking are you both graduates in Physics or lecturers or other please do let me know. You may PM me if you want.

    Thanks
     
  6. Aug 19, 2010 #5
    I have a degree in Aesthetic Studies...
     
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