Stephen A Lawrence wrote: > You've said two different things here: "the strength of the > field will drop", and "the voltage drops". The dielectric will > _certainly_ affect the voltage, just as interposing a charged > parallel plate capacitor would affect the voltage (which would > reduce it by the voltage to which the capacitor had been > charged). As an aside, that is how a polar dielectric acts to > increase the capacity of a parallel plate capacitor versus using > an air dielectric: for any particular net charge on the plates, > interposing it reduces the voltage between the plates; > consequently the ratio of charge to voltage increases.
> What it won't do, however, _if_ it's a large flat sheet and the > field is perpendicular to it (and it carries no net charge), is > have a significant effect on the electric field on either side > of it ... any more than a large parallel plate capacitor would. > If you disagree please explain either (a) how a polar dielectric > in an E field differs in its field from a charged capacitor or > (b) how either one of them has a large effect on the field > outside the "plates". Let's make sure we're talking about the same thing. I'm a little concerned that we're talking past each other about different but related subjects. Forget about the terms "voltage" and "field strength". What I'm addressing is the physical force of attraction or repulsion between electrically charged objects, whatever terminology you want to apply to it. Let me propose a practical model. We have a charged metal object, a sphere, for example. It has been charged to, say, 20kV. The sphere is electrically isolated and there is no current source beyond the initial charge. There is no significant corona leakage within the time frame of our demonstration. To be classical, we have a pith ball hanging by a length of thread nearby and it is attracted to the charged sphere, as evidenced by the angle at which the thread inclines from the vertical toward the sphere. The pith ball has been placed at a distance that will not allow it to touch the charged sphere. Are you saying that an uncharged polar dielectric object with a high K placed between the charged metal sphere and the pith ball will have no effect on the attraction between the pith ball and the sphere? In other words, will the angle of the thread and the distance between the pith ball and the sphere remain unchanged? M. _______________________________________________ Join Excite! - http://www.excite.com The most personalized portal on the Web!
