Recent content by jbunten

Can either method find a global minimum?

So just to recap, in principle for the situation described in bold, In principle you could work out the increase in entropy dS for that system when heating it at constant volume, plug it into the thermodynamic identity and get the same result you would if you had used the heat capacity and...

Thanks to both of you this is now much more clear in my head, I really appreciate it!

OK. So I see all the maths works and now I'm trying to get an intuitive understanding of this. Here's what I've reasoned out: VdP doesn't need to be in this expression because an increase in pressure at a constant volume doesn't mean any work so don't include it. Also, the expression...

We have the expression: dE=TdS-PdV if increasing temperature or pressure affected internal energy the dT and dP terms would be necessary to state or otherwise to use partial derivatives and specify T and P as constant. Am I thinking in the wrong way?

OK, so energy, being an extensive variable, gets expanded in terms of all the other extensive variables, giving you a relation SdT=VdP (assuming chemical potential = 0 for simplicity) which if you then substitute back into your differential equation for dE gives you the dE=TdS-PdV result...

I understand why dE=TdS-PdV ...[1] at constant temperature and pressure Also, I see that F=E-TS and therefore dF=dE-SdT-TdS ...[2] and how combining [2] and [3] gives dF=-SdT -PdV QUESTION: shouldn't [1] be expressed as dE=TdS+SdT-PdV i.e if you're going to substitute...

A good source for definition of thermal average can be found here in the Planck Distribution Function chapter on here: http://en.wikibooks.org/wiki/Statistical_Mechanics/Thermal_Radiation better late than never I suppose.

Thanks for your excellent reply mathman.

Thanks!

Someone must know??!

Title says it all :)

I am reading that diffusive scaling in one dimension means that "increasing the size of a cell by a factor of 20 increases average diffusion time by a factor of 400". I can't find anything on diffusive scaling. Can anyone give me an explanation of this? Thanks

I'm trying to understand a paper (Magnasco, 1993) which discusses "Forced thermal ratchets". It gives a Langevin equation as: \stackrel{.}{x} = \epsilon(t) + f(x) + F(t) where x (a cyclic coordinate) describes the state of the ratchet, f(x) is a force field, F is a driving force and...

I'd just like to add that although sometimes physics can seem extremely difficult, this is often because you need to understand the more basic foundations, and then it becomes a lot more clear. This is not to say it *isn't* difficult of course, but remember that when you were four years old...