Hi Marshall, we certainly disagree on this one, check out positive and negative doping of semiconductors, obviously there can be more and looser - so to speak - electrons within lattice structures and more than there are protons to balance them. Further, due to the strains between crystal interfaces - polish some metal and etch it and you'll see them - various parts of any piece of metal will have different quantities of electron propagation at some voltage across the particular crystal interfaces. Also the inherent resistance of various metals and alloys - compare silver and inconel or even iron for instance - gives an illustration of the confused and by no means linear effect of electric pressure on so-called "free" electrons in metals. In other words, although the signal travels at just slightly less than the speed of light, and though I grant that increasing the pressure on an electron will tend to cause it to be more likely to move, the effective increase in current in, say, a wire is overwhelmingly a matter of getting more electrons moving than getting any one, or billion, of them to move faster from one end of the wire to the other. More current causes more heat, causes less current. Anyhow, that's what I was taught; perhaps the sands have shifted from under my feet, that has happened before.
Superconductivity is another matter, and I don't know anything about electron flow in superconductors. Take care, Malcolm On Mon, 2008-09-15 at 11:18 -0400, Marshall Dudley wrote: > Malcolm wrote: > > Ummm, > > > > On Fri, 2008-09-12 at 15:36 -0005, M. G. Devour wrote: > > > >> Dear Neville, > >> > >> You write: > >> > >>>> [The actual linear velocity of the electrons within the wire is > >>>> proportional to the current: Zero with the switch off, and limited by > >>>> ohm's law, ie. total circuit resistance and voltage, when on.] > >>>> > >>> As a simple example...the higher the current, the quicker the 'flow', > >>> (forgetting ohms law for the moment)... yes? > >>> > >> The higher the voltage or lower the resistance, then yes, the current > >> will be higher, which means the electrons are moving faster in the > >> wire. > >> > > > > well not really, though more of them will be moving in the (roughly) > > same direction past a given point; that is, after all, what "Current" > > is. > > > > It's not that the electrons run faster from end to end, hence increasing > > the current; it's that higher voltage crowds them in more densely: for > > yet another very imperfect analogy, more get stuffed into the subway > > train, but the train doesn't go any faster, and so more get out at their > > destination, per unit of time (hours if you live in New York!) > > > The number of electrons inside a wire is constant, and independent of > any voltage on the wire, it will be equal to the number of protons in > the nucleus, always. Now if you put high voltage on a wire, the number > of electrons on the surface will vary due to the capacitance effects on > the surface, but this is trivial compared to the number of electrons > inside the wire. If what you were saying were true, then applying a > positive voltage to a wire that is grounded would result in a reduction > of current as the voltage is increased, since that would result in fewer > electrons in the wire. Ohms law is correct whether the wire has a > positive voltage or negative voltage on it since the voltage on a wire > has no effect on the number of carriers inside the wire. It only > affects their average velocity. Think in terms of a pipe with water. > Adding pressure does not change the amount of water in the pipe, except > by any little amount the pipe stretches, but adding pressure drop from > one end of the pipe to the other changes the velocity of the water in > the pipe, thus the flow increases. Voltage equals pressure, current > equals flow. > > It is actually pretty simply to do the math. An electron experiences a > pull when in an electric field. This pull is the vector product of the > voltage gradient and the charge on the electron. The electron > experiences an acceleration which is mathematically equal to this force > divided by the mass of the electron. However before it has gone far, it > bumps into an atom, and loses it's velocity, and the kinetic energy is > converted to heat. This is what give wire resistance. Now if you can > couple the electrons together into pairs, they can actually flow without > bumping into the atoms, and that is how a superconductor, which has no > resistance, works. > > Marshall > > Marshall > > > > > > -- > > The Silver List is a moderated forum for discussing Colloidal Silver. > > > > Instructions for unsubscribing are posted at: http://silverlist.org > > > > To post, address your message to: silver-list@eskimo.com > > > > Address Off-Topic messages to: silver-off-topic-l...@eskimo.com > > > > The Silver List and Off Topic List archives are currently down... > > > > List maintainer: Mike Devour <mdev...@eskimo.com> > > > > > > > > > > > > > > > >
