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 electrons from 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 battery electrodes 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" continuously around the atom). >Therefore an electric field IS NOT the same as an EMF. > Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/Project.html
