Re: [Phys-L] circular definition of "success" .... was: standard DC circuits

[brian whatcott <betwys1@sbcglobal.net>]

On 11/29/2013 10:04 PM, Bernard Cleyet wrote:
> Is this a simple Gauss’ law prob.?
>
> bc ...
>
> On 2013, Nov 29, , at 19:44, LaMontagne, Bob <RLAMONT@providence.edu> wrote:
> > Sorry, meant to say that the wire is parallel to the field.
> >
> > Bob
> > ________________________________________
> >
> > Sent: Friday, November 29, 2013 10:36 PM
> >
> > Suppose we have a uniform electric field and we place in the field a finite length straight wire which is grounded at both ends. What is the field in the wire and what do the surface charges look like?
> >
> > Bob at PC
It is an extraordinary luxury that is open to me, but denied to anyone 
working as a physics teacher: that I can type any single thing that I 
feel moved to, and as like as not, it will pass to the phys-l list. This 
is an uncomfortable factor to those well-intentioned people who feel 
that teachers' understanding should not be polluted by nonsense, 
supposing that teachers should have a touch-stone of 
best-available-truth - or if not truth, at least facts, as best known.
   But  teachers will notice that a dialog can help internalize some 
ideas of value, if only from the swift rebuff that nonsense may politely 
evoke.

So let me think about this: a uniform field, with what may be thought of 
an enforced region of zero field inserted in it? Perhaps visualized at 
two parallel plates of infinite extent, and between them, two small 
disks both parallel to the infinite plates, connected with a wire. The 
infinite plates would have some generator of a steady voltage applied, 
so that after an infinite time interval, the uniform electric field is 
everywhere established, everywhere except on these two internal plates 
that is. And at some point in the past, there was a displacement current 
which mechanized the polarization of both internal plates, so that now 
we can visualize a uniform field - of sorts -  from the interior plate 
surfaces to the external planes. I could suppose, relying only on 
intuition that the wire surfaces attaching the interior plates are 
indeed devoid of surface charge, if only the shielding effect of the 
interior plates is large enough. And now I have a difficulty - if I 
shrink the area of these internal plates, then the electric field will 
start making a distinct difference to the surface charge of that 
internal wire.    And that is as far as my evidently insufficient 
intuition will take me. Pity!

Brian Whatcott   Altus OK