If $q$ is the charge per unit area on the surface of a conductor, then the electric field intensity at a point on the surface is

‘Inside a conductor electrostatic field is zero’. Explain.

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.

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

An empty thick conducting shell of inner radius $a$ and outer radius $b$ is shown in figure.If it is observed that the inner face of the shell carries a uniform charge density $-\sigma$ and the surface carries a uniform charge density $ '\sigma '$

If a point charge $q_A$ is placed at the center of the shell, then choose the correct statement $(s)$