- #1
mischmi
- 5
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- TL;DR Summary
- Molecular Ratchet;
Hi all.
Feynman writes:
https://en.wikipedia.org/wiki/Brownian_ratchet
Feynman writes:
https://www.feynmanlectures.caltech.edu/I_46.htmlWhen the damping happens, of course, the energy that was in the pawl goes into the wheel and shows up as heat. So, as it turns, the wheel will get hotter and hotter. To make the thing simpler, we can put a gas around the wheel to take up some of the heat. Anyway, let us say the gas keeps rising in temperature, along with the wheel.
https://en.wikipedia.org/wiki/Brownian_ratchet
- Does emerging of temperature differences supposedly violate the 2nd law? (yes?)
As soon as a temperature difference occurs, e.g. a Carnot process could work. - or 2nd ratchet in the opposite direction? Energy transfer and temperatures would balance each other out, but the work on the load would remain
- Are Feynman's explanations of the molecular ratchet still valid?
I am not convinced by his famous explanations. Is there already any reasonable criticism on his approach out there? Only the case with same temperatures is interesting. Nothing surprising with different temperatures.
Feynman could/should use or invent a mechanically better working ratchet, different kind of freewheel, or one working continuously. Do Feynman's ratchet and pawl jiggle independently? This is not how ratchet should work. - Would just biased movement of a kind of ratchet/freewheel, without load or "useful work" supposedly violate the 2 low? (yes?)
- Would a (working) molecular ratchet definitely violate the 2nd law of thermodynamics? (no?)
The ratchet is made up of separate Brownian particles with limited and known mobility, which reduces the entropy of the entire system. (similar to the explanation of Maxwell's demon) - Is the 2nd Low Of Thermodynamics the adequate context in studying the kinetic gas theory, spatially molecular ratchet? (no?)
Kinetic gas theory deals width microscopic, reversible, Newtonian, at particle level (even if "only" statistical) model, and has fluctuations. Thermodynamics don't, is a macroscopic view. Sure, in limit both give equal statements. (Isn't it as you would say "Newton was wrong, because of relativity...", just a question of taking a closer look?)