The magnitude of electric field on the surface of a uniformly charged metalic spherical shell is $E$. If a hole is made in it using a insulating device, then the magnitude of electric field in the hole will be

Two charged spherical conductors of radius $R_{1}$ and $\mathrm{R}_{2}$ are connected by a wire. Then the ratio of surface charge densities of the spheres $\left(\sigma_{1} / \sigma_{2}\right)$ is :

For the situation shown in the figure below, mark out the correct statement

A spherical conducting shell of inner radius $r_1$ and outer radius $r_2$ has a charge $Q. $

$(a)$ A charge $q$ is placed at the centre of the shell. What is the surface charge density on the inner and outer surfaces of the shell?

$(b)$ Is the electric field inside a cavity (with no charge) zero, even if the shell is not spherical, but has any irregular shape? Explain.

Two spheres of radius $R$ and $2R$ having charge $Q$ and $2Q$ respectively are placed far away from each other. How much charge will flow when key $'k'$ is pressed ?

A non uniformly shaped conductor is charged then at it's sharpest point