$A$ hollow metal sphere of radius $10 \ cm$ is charged such that the potential on its surface becomes $80 \ V$. The potential at the centre of the sphere is . . . . . . . (in $V$)

Eight identical charged drops combine to form a single large drop. If the potential of each small drop is $10 \ V$,then the potential of the large drop will be ........ $V$?

Two conducting spheres of radii $r_1$ and $r_2$ are equally charged. The ratio of their potentials is (potential of $r_1$ to potential of $r_2$):

If a charged spherical conductor of radius $10\,cm$ has potential $V$ at a point distant $5\,cm$ from its centre,then the potential at a point distant $15\,cm$ from the centre will be

$A$ solid sphere of radius $R$ is charged uniformly. At what distance from its surface is the electrostatic potential half of the potential at the centre?

Consider a fixed uniformly charged insulating sphere with radius $R$ and total charge $+Q$. $A$ point charge $-q$ $(q \ll Q)$ with mass $m$ is released from rest at a distance of $3R$ from the centre of the charged sphere. When the point charge reaches the surface of the sphere, its speed is:
($\epsilon_0$ is the permittivity of vacuum, neglect gravitational forces).