Re: Electrostatics problem

["Miguel A. Santos" <msantos@ETSE.URV.ES>]

>         Doesn't Gauss's law solve the problem?  (See Santos' posting).
>                                         Regards,
>                                                 Jack
 ...and with it you conclude that no inner cavity in a conductor will
contain a electrostatic field. But still one can see such statements
telling the students that the 'inner' (let's call it so) surface of
an open cylinder won't have no charges. One of our V.der Graff machines
(is it the one from Edmunt S.?) comes with the typical guide on electrostatic
experiments which say that. There you have such an open cylinder which has
two sucha polystirene (?) small balls hanging from the 'inner' surface.
The cylinder gets attached horizontally to the V.d.G machine. Two other
balls are hanging outside close to the 'outer' surface. When you switch on
the V.d.G. machine the outer ball separate from each other while the
inner ones seem not to feel anything at all. It is not even the case
the cylinder is much more longer than its radius. Following those guides,
the conclusion seems to be that the 'inner' surface holds no charges, ergo
E=0 at it. I don't believe that.
        Regards,
                Miguel A. Santos