On 8/13/07, Horace Heffner <[EMAIL PROTECTED]> wrote: > > On Aug 13, 2007, at 3:51 PM, Terry Blanton wrote: > > > Interesting exchanges. > > > > If a pair of wires are 3 x 10^10 cm long; and, a potential is applied > > to the ends of the wires with a load resistor on the other end, I have > > two simple questions: > > > > 1) How much time passes before the first electron drifts through the > > load center point assuming the load is only 2 cm long? > > The first current will appear in at most a few seconds.
Wouldn't Poynting's theorem say almost exactly 10 seconds? Can we understand by what mechanism? > > > > > 2) How much time passes before the first electron to leave the source > > of potential arrives at the load? > > It will take a very long time. It depends on the free charge density > in the metal, the wire cross sectional area, and the current. A very > rough number for electron drift speed for estimating purposes might > be 10 cm/h. Thats roughly 3x10^9 s, or 9.5 years. > > > > > > Simple questions, eh? > > Yeah, when you have a handy cheat sheet. 8^) > > Our very own Bill Beaty has a nice write-up on this subject at: > > http://amasci.com/miscon/speed.html Thanks, interesting document on drift. Terry
