Difference Between Thin and Conductive charge configurations

[Rawrzz]

Difference Between "Thin" and "Conductive" charge configurations

Is there any difference computationally between say a thin spherical insulating shell and a thin conductive shell ?

Can you create a capacitor with two thin insulating shells, one smaller than the other ?

I see most textbooks explicitly say that capacitors must be conductors. Is this so ?

 

[UltrafastPED]

The charge enters the capacitor from outside - with an insulator the incoming charge is stuck in one spot, so it would make a lousy capacitor. With conducting surfaces source charges can flow so that the entire surface is charged (both plates/spheres).

The region between the conductors is the insulator; the charges on the plates induce small movements in the molecules of the conductor - they "polarize" the material, but no charge moves more than a few nanometers.

 

[Rawrzz]

Say a charge is already uniformly distributed on the thin spheres. Can you talk about capacitance then ? I realize that it is the practicality of charging that is the problem, but textbooks talk about uniform charge on insulators all the time.

 

[UltrafastPED]

It wouldn't make a workable capacitor, but it could have a capacitance; see the definitions:
http://en.wikipedia.org/wiki/Capacitance

and here:

http://en.wikipedia.org/wiki/Body_capacitanceCapacitive sensors are an important technology. But just because something has a capacitance does not mean that it would work as a capacitor ... for that to be true it must also satisfy the voltage/current relationship.