On May 23, 3:15 pm, "operator jay" <n...@none.none> wrote:
<vikraman.choudh...@gmail.com> wrote in message
news:1179941121.027325.227400@q19g2000prn.googlegroups.com...
What do you mean by the drift velocity of charge carriers in a
conductor when an electric field is applied across it? Is it the
average velocity of motion of the charge carriers or is it the
terminal velocity attained by it when the force on it is
neutralised?
(diffrerent sources cite it differently!!)
I don't think there IS a 'terminal velocity when the force on it is
neutralized'. I think an electron is continuously pinballing around
due to thermal motion (like a molecule in a gas).
Yes... assuming that classical picture means anything.
It seems to me that if we accept that picture, we still could make
some sense of "terminal velocity" if we were willing to take time or
ensemble averages. Starting out with an ensemble of electrons
accelerating under an external field, the ensemble average velocity
would approach the terminal velocity like that of a single particle in
a dissipative medium.
It's interesting to notice that while we might think of the "electric
field being nulled out by friction", in detail the electron is only
repsonding to electric fields! The time averaged field seen by an
electron at time averaged constant velocity is zero: presumably
achieved by the prepoderance of collision events with nuclei tending
to retard the electron's motion, based on its average velocity.
The applied
electric field gives a slight tendency toward direction along the
conductor. The 'average velocity of motion' gets my vote. A sample
calculation in Serway gives a drift velocity magnitude on the order of
10^-4 m/s for a modestly loaded conductor.
.
