Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Prooving 2 law

  1. Dec 25, 2007 #1
    can anyone proove "kelvin plank" statement of second law of thermodynamics or atleast show that it is always followed in any cyclic process.......
  2. jcsd
  3. Dec 28, 2007 #2
    am i gone mad ,no one knows it.......come on
  4. Dec 28, 2007 #3

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    I think this question is asking you to prove that the Kelvin Planck statement of the second law follows or is equivalent to the Clausius statement of the second law.

    First of all, you should state the Kelvin Planck statement of the second law and also state the second law (Clausius statement).

    Then assume that the Clausius statement is not true (heat flows from cold to hot without adding work) and show that it follows that Kelvin Planck is not true. So not-Clausius is false (and not-KP is false): ie.Clausius must be true (and so Kelvin Planck must be true).

    Hint: assume that heat Q can flow from cold to hot without doing work, then put a heat engine in there which takes the same amount of heat (Q) from the hot reservoir as flows from the cold and produces W work delivering Q' heat flow to the cold reservoir. You can see that the hot reservoir is not really doing anything (Q flows in and Q flows out) so you can ignore it and just consider Q flowing from the cold reservoir to the heat engine.

    Last edited: Dec 28, 2007
  5. Dec 29, 2007 #4
    but what i mean is to show that the statement
    "kelvin plank"
    "heat cannot be converted into work with 100% efficiency(without giving some to cold body)"

    is followed in every cyclic process ,without using other forms of the 2 law or carnot
    cycle or any such statement which is a part of second law or uses it .

    i.e to prove it independently

    because it will automatically prove every other part of it except the one including the concept of entropy which i think can,t be prooved..

    well i have made some progress in it but i am not sure that my proove is genuine one or not hence i wanted someone to come up with some other more rigourous methods to do it.

    but thanks for your reply...:approve:
    Last edited: Dec 29, 2007
  6. Dec 31, 2007 #5
    search for proof

    well if you all remembered i recently asked the question about prooving(not deriving) 2 law
    but no one gave me the answer i wanted. so i was left to do on my own ,well i came up with an
    analysis but dont know whehter it is right or wrong
    so here i put to everyone to analyse it and check

    Attached Files:

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Prooving 2 law
  1. Newtons Laws 2/3 Why's (Replies: 9)

  2. Prooving the flux rule (Replies: 0)