Final answer:
A point charge placed outside a grounded sphere induces charge separation within the sphere. The sphere becomes negatively charged, and the electric field inside remains zero. The point charge interacts with these induced charges, resulting in an attractive force.
Step-by-step explanation:
When a point charge is placed at a distance d from the center of a grounded conducting sphere of radius a, the electrical interaction involves the process of induction. The electric field from the point charge induces a separation of charges within the conductor, resulting in an induced positive charge on the nearest side and an induced negative charge on the far side. Since the sphere is grounded, it allows charge to flow from the Earth to neutralize the induced positive charge, leaving the sphere with an induced negative charge opposite to the point charge.
The electrostatic force exerted by the point charge causes a distribution of charge within the sphere in such a way that the electric field inside the sphere remains zero. This is consistent with the principle that the electric potential inside a conductor in electrostatic equilibrium is constant. The induced charges create an external electric field, but the interior of the sphere experiences no electric field since it is a conductor in electrostatic equilibrium.
By Coulomb's law, the force between the point charge and the induced charge on the sphere can be calculated. The induced charges on the sphere lead to an attractive force between the sphere and the point charge since they are of opposite signs.