Two concentric spheres $A$ and $B$ are kept very near to each other. $A$ is negatively charged and $B$ is earthed. The true statement is

$(A)$ Charge on $B$ is zero

$(B)$ Potential at $B$ is zero

$(C)$ Charge is uniformly distributed on $A$

$(D)$ Charge is non uniformly distributed on $A$

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

Two identical conductors of copper and aluminium are placed in an identical electric fields. The magnitude of induced charge in the aluminium will be

‘At the surface of a charged conductor electrostatic field must be normal to the surface at every point’. Explain.

A thin-walled, spherical conducting shell $S$ of radius $R$ is given charge $Q$. The same amount of charge is also placed at its centre $C. $ Which of the following statements are correct ? 

 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 the inner surface of the shell is earthed, then identify the correct statement(s)