and A hollow conducting sphere of inner radius r₁ outer radius 12 has a charge Q on its surface. A point charge-q is also placed at the centre of the sphere. (a) What is the surface charge density on the (i) inner and (ii) outer surface of the sphere? (b) Use Gauss' law of electrostatics to obtain the expression for the electric field at a point lying outside the sphere.

and A hollow conducting sphere of inner radius r₁ outer radius 12 has a charge Q on its surface. A point charge-q is also placed at the centre of the sphere. (a) What is the surface charge density on the (i) inner and (ii) outer surface of the sphere? (b) Use Gauss' law of electrostatics to obtain the expression for the electric field at a point lying outside the sphere.