----- Original Message ----- From: [email protected] Date: Tuesday, October 13, 2009 5:28 pm Subject: Re: correction /Re: [Vo]:The Electric Field Outside a Stationary Resistive Wire Carrying a Constant Current
> In reply to Harry Veeder's message of Mon, 12 Oct 2009 02:35:43 - > 0400:Hi, > >Ok, I guess it is necessary to distinguish between a capacitor, a > >battery and an EMF. Both a battery and a capacitor can produce a > >current for a _limited_ period of time, whereas an EMF can produce a > >current for an _unlimited_ period of time. > > There ain't no sich animal. Nothing runs forever. The universe is a > big battery, > and it's running down. Who can say for sure? Who wants to say for sure? IMO, the application of some currently recognized physical principles governing machines to the entire universe is like painting oneself into a (spiritual) corner. Newton was aware his clockwork universe would run down so he allowed God to periodically intervene in his clockwork universe to wind things up. On a deeper level he believed creation was more than what could be explained by his axioms/laws. > You can only maintain an EMF at a "constant" > level, when > current is flowing in a resistive circuit, by supplying energy > IOW you have to > "pump" the electrons from the low voltage side back to the high > voltage side. > This is usually done with a changing magnetic field (i.e. a > generator or > dynamo), which once again introduces a step in the voltage going > around the > circuit. You can picture the voltage at each point as single > rotation of a helix > with a vertical axis with the begin and end points joined by a > straight vertical > line. That vertical line is where the energy is added. Energy is > lost to > resistance as the current runs around the helix. I agree. The point I have been trying to make is that an EMF is technically not same thing as electrical field. They are different animals. > > > >With that in mind, let me refine the question. Can a current which > runs>indefinitely (and does not occur in a superconductor) be > explained>consistently only with the concept of an electric field? > [snip] > Regards, > > Robin van Spaandonk > > http://rvanspaa.freehostia.com/Project.html > Harry
