A thin, metallic spherical shell carries a charge Q . A point charge q is located at the centre of the shell and an additional charge q₁ is placed outside it, as shown in the figure. All three charges are positive. The force acting on the charge at the centre is

Step-by-step solution

The point charge q at the centre of the metallic spherical shell induces a charge -q on the inner surface of the shell. Since the charge q is placed exactly at the centre, the induced charge -q is uniformly distributed over the inner surface. The electric field produced by this uniformly distributed charge at the centre is zero. Due to the property of electrostatic shielding in conductors, the electric field inside the cavity of the conductor due to the external charge q₁ and the charge on the outer surface of the