Question

n drops each of radius 'r' and carrying charge q combine to forn a big drop. Calculate potential of the big drop. (hint: volume of n drops = volume of big drop) V= kqn^2/3 / r

Answer 1

radius of big drop = R say..
volume of big drop =   N * 4 π/3 * r³  = 4 π/3  * R³
    =>      R = ∛N * r   
charge on big drop = N q

potential on the surface of small drop = (1/4πε) q/r
potential on the surface of big drop = (1/4επ)  N q / R
           $V = k \frac{q N^{2/3}} {r}$