Answer this question .Physics - class 12-electrostatic potential and capacitance

To make the charge escape to infinity, we need to ensure that the energy of the charge is zero or greater. For negative values of energy of q, it will not be able to escape the Coulombic pull of the ring.
(i) For q is positive, the electrostatic potential energy of the ring-charge system is already positive and equal to. Hence it will reach infinity by itself due to the electrostatic repulsion.
(ii) If q is negative, the electrostatic potential energy is, and hence we need to provide the same amount of energy from outside to make it zero.
Hence