1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 2nd Law of Thermodynamics

  1. Mar 7, 2016 #1
    I have a quick question concerning the 2nd law of thermodynamics. So my textbook uses an illustration to explain how the violation of the Clausius statement of the 2nd law implies a violation of the Kelvin-Plank. But while looking over the diagram I stated thinking about a certain situation. In the diagram two systems are shown communicating thermally with the same reservoirs. The on on the left is in violation of the Clausius statement while the one on the right is thermodynamicaly sound as its own system. But when you draw the boundary line around the two cycles and the cold reservoir, it violates the Kelvin-Plank statement, which is perfectly okay. However, what if a system boundary were drawn around the cycle to the right and the cold reservoir, making a system consisting of those two entities. It would seem that the system would be communication thermally with only one reservoir (the hot one) yet generate a net output of work, which violates the Kelvin-Plank statement. Any insight would be appreciated.

  2. jcsd
  3. Mar 7, 2016 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    Cannot load the image.
    I cannot see but it sounds like you have a system with a hidden internal energy source: the heat reservoir inside the box.
    It still counts.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted