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Re: Thanks....

jc: ""
Of course I meant 'Fermi velocity' . To take a typo and make it into a question is 'sophomoric', Jneutron.""

Lighten up, dude..
jc: ""
I don't think that I ever saw the response from the 'grad student' of Dr. Hummel's. Why don't you post it sometime? ""
Under no circumstances, will I post another's private e-mail response on forum. Under no circumstances will I send a private e-mail to another. Under no circumstances will I disclose information that has been transferred via private conversation. Never, even if doing so supported my position.

I would hope you live by the same rules.

jc: ""
I contacted Dr. Hummel, himself, about the difference between drift velocity and Fermi velocity, and how it changed the situation. He told me that the classical expression using drift velocity to predict current flow was a pretty good approximation for many situations, BUT that it failed with many elements such as sodium, etc. That is why the quantum expression of the same phenomena is so necessary. The quantum expression does not exclude a 'virtual' drift velocity, but it does change the number of donor electrons to some other value that is different from the classical expression. If the number of displaced electrons per unit volume is actually different in the quantum mechanical case, then it seems to me that the actual drift velocity would be different than the classically derived drift velocity, because you have a different number of electrons per unit volume to work with. How much different is still a question that I have, because it has NOT been stated by anyone, including Dr. Hummel.
However Dr. Hummel did state in (7.16) on p.82 that: j=v(F)eN' rather than j=Nve, where v in this case is the classical drift current, and v(F) is the Fermi velocity. This also inplies that N' should be a much smaller value than N, because the Fermi velocity is so fast, relative to the classical drift velocity. What do you think? ""

I think your repeating stuff that was discussed years ago.

I think sodium doesn't make a very good speaker wire.

And..

I think the quantum understanding is good for now, until the next paradigm shift. (had some nobel laureates give talks here in the last month...holy mackeral.)

The point that I was making all those years ago was this: If the current model that is being used for the description of the gross movement of electrons through a metallic conductor is adequate for the task, then there is no reason to attempt to use a far more complex and unrealizeable (equation wise) solution for use by the masses. Drift velocity is a model. It worked decades ago, it will work centuries into the future. There is no need to invoke a Fermi sphere nor it's displacement for the purposes of electrical engineering. Simple..

The right tool for the right job. If the tool is too complex for anyone to use, then it should not be called a tool.

Cheers, John

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