Shown in the figure is a shell made of a conductor. It has inner radius $a$ and outer radius $b$,and carries a total charge $Q$. At its centre is a dipole $\vec{P}$ as shown. In this case,

• A
  Surface charge density on the inner surface of the shell is zero everywhere.
• B
  Electric field outside the shell is the same as that of a point charge $Q$ at the centre of the shell.
• C
  Surface charge density on the inner surface is uniform and equal to $\frac{(Q/2)}{4\pi a^2}$.
• D
  Surface charge density on the outer surface depends on $|\vec{P}|$.