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.
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? harry ----- Original Message ----- From: mix...@bigpond.com Date: Sunday, October 11, 2009 5:03 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 Thu, 08 Oct 2009 23:39:47 - > 0400:Hi, > [snip] > >The electrons must be recirculated in order to maintain a steady > >current. If an electric field is the same as an EMF, then the > electric>field must form a closed loop, otherwise electrons would > pile up at the > >'+'electrode where the electric field ends in your depiction. > > ...but they *are* "piling up"! (Actually they are already "piled > up", and the > size of the pile is decreasing, IOW they are "piling down" ;). > > In a capacitor there is a pile of electrons on one electrode, and a > paucity on > the other. When the two are connected by a wire (of any shape), the > electronsfrom the pile flow through the wire to the other electrode > until both are equal > at which point in time, the current stops (assuming the wire has no > inductance).In practice of course the wire always has some > inductance, so the current keeps > going for a little while after zero charge has been reached due to > the collapse > of the magnetic field around the wire, resulting in an opposite > charge on the > capacitor. This gives rise to the decaying wave form seen after you > throw the > switch that established the original connection. > > In the case of a battery, the "pile" consists of the atoms of the > batteryelectrodes that either accept or donate electrons (depending > on the electrode). > > >Of course > >a closed electric field loop is not allowed in theory, so the > concept of > >an electric field cannot > >be used in a logically consistent manner to *fully* explain the > current. > An electric field can and does explain the current, it's just *not* > a closed > loop at the same voltage. The only place where a current flows at > the same > voltage is in a ring of superconducting material where it flows > without loss and > without an EMF at zero voltage drop. (one may also argue that an > atom itself is > a superconductor allowing the electrons of the atom to "flow" > continuouslyaround the atom). > > >Therefore an electric field IS NOT the same as an EMF. > > > Regards, > > Robin van Spaandonk > > http://rvanspaa.freehostia.com/Project.html > >
