The ‘Brownian ratchet’ and its relevance to the second law of thermodynamics.

YoshiBeans

My question is regarding the reason why the Brownian ratchet fails to negate the second law.

The explanation that I have been told relates to the fact that the molecules in the second chamber would interact with the 'pawl' in a similar manner to those interacting with the paddle wheel, negating the overall useful rotation.

I have also been told that if T1 is higher than T2, then it will produce useful work, but that this complies with the laws by acting like a heat engine.

My question is: How can the same failure to extract useful work be explained if there was a vacuum in the second chamber? This would negate the temperature comparison, and would seem to allow the extraction of work from the first chamber.

I would appreciate any available illumination. Thank you.

guillefix

I would really like to know this too.