Given, number of mercury drops, n=512 Voltage of each drop, V=2V Let r,R be the radius of drop small and combined spherical drop, respectively. Now, when all drops are joined into single drop, volume remains constant, i.e. 512×
4
3
πr3=
4
3
πR3 ∵V=
kq
r
=2. . . (i) ∴Vnet =
kQ
R
where, Q be the charge of bigger sphere. ⇒Vnet =
k×512q
8r
. . . (ii) On dividing Eq. (ii) by Eq. (i), we get