# Field inside a conductor

Gold Member

## Homework Statement

consider two concentric shells, the smaller one has inner and outer radius a and b, the larger one has IR and O.R. c and d. Inner shell has total charge -2q and outer shell has total charge +4q.
NOTE-This is a random situation I created to explain my doubt properly, so we aren't actually supposed to find anything, its just a conceptual doubt which I have elaborated upon in "attempt at a solution" since it is mandatory to fill the section on PF.

## Homework Equations

All electrostatics related formulas

## The Attempt at a Solution

I went ahead and found the field in the region between the shells (i.e b<n<c where n is the distance from common center) by taking a gaussian surface of radius n; ##q_{enclosed} = -2q## so the field is -2kq/r^2. My doubt is that since this region lies inside the larger shell which is a conductor; shouldn't the electric field at all points inside be zero? why is it non-zero here?
I'd be really grateful for some insight. Thank you.

Doc Al
Mentor
My doubt is that since this region lies inside the larger shell which is a conductor; shouldn't the electric field at all points inside be zero? why is it non-zero here?
Within the hollow area there will certainly be a non-zero field and that's not an issue. It's only within the conducting material itself that the field must be zero.

Thus, in your example, only at points r where a<r<b & c<r<d must the field be zero. Everywhere else is fair game for a non-zero field.

Krushnaraj Pandya
Gold Member
Within the hollow area there will certainly be a non-zero field and that's not an issue. It's only within the conducting material itself that the field must be zero.

Thus, in your example, only at points r where a<r<b & c<r<d must the field be zero. Everywhere else is fair game for a non-zero field.
ohh...right, thank you very much :D