The electric potential at a distance $r$ outside a uniformly charged sphere (where $a$ is the radius of the sphere) is proportional to:

$A$ conductor with a positive charge:

$A$ particle $A$ has a charge of $+q$ and a particle $B$ has a charge of $+9q$. Both particles have the same mass $m$. If both particles are released from rest through the same potential difference,the ratio of their speeds will be .......

Two rings of radius $R$ are placed coaxially at a distance $R$ apart. They carry charges $Q_1$ and $Q_2$ respectively. How much work is required to move a charge $q$ from the center of one ring to the center of the other?

$A$ small sphere of radius $r_{1}$ and charge $q_{1}$ is enclosed by a spherical shell of radius $r_{2}$ and charge $q_{2}$. Show that if $q_{1}$ is positive,charge will necessarily flow from the sphere to the shell (when the two are connected by a wire) no matter what the charge $q_{2}$ on the shell is.

If $50 \, J$ of work must be done to move an electric charge of $2 \, C$ from a point,where potential is $-10 \, V$ to another point,where potential is $V \, V$,the value of $V$ is ......... $V$.