A charged ball $B$ hangs from a silk thread $S$ white makes an angle $\theta ,$ with a large charged conducting shut $P,$ as shown in figure, Fig. 3.84. The surface charge density $\sigma$ of the sheet is proportional to

 

Consider three concentric shells of metal, $A,B$ and $C$ are having radii $a,b$ and $C$ respectively are shown in figure (Fig. 3.85). Their surface charge densities are $\sigma ,-\sigma$ and $\sigma$ respectively. Calculate the electric potential on the surface of shell $A$

Figure (Fig. 3.86 ) show three spherical and equipotential surfaces $A,B$ and $C$ round a point charge $q.$ The potential difference $V_A-V_B=V_B-V_C$
If $t_1$ and $t_2$ be the distance between them. Then