Question

A spherical conducting shell of inner radius and outer radius has a charge ‘q'. A charge ‘q' is placed




at the centre of the shell.




(a) what is the surface charge density on the (i) inner surface, (ii) outer surface of the shell?




(b) write the expression for the electric field at a point x> from the centre of the shell.

Answer 1

The spherical shell has +q charge, it is evenly spread on the outer surface(as it is the property of conductor), now how did it get positively charged? When electrons travelled from outer side to inner side. So, inner side has -q charge.

a) surface charge density is total charge by surface area

so, for inner side it will be -q/4πr^2

r is inner radius.

Likewise u can find it for outer side.

b) For a point outside the shell the charge will be assumed to be concentrated at the centre, so u can directly use Coulomb's law for distance x.

Enjoyed the question. : )