What is the order of electric potential generated by a Van de Graaff generator?

The potential at a point,due to a positive charge of $100\,\mu C$ at a distance of $9\,m$,is

$A$ proton is accelerated through a potential difference of $1 \,V$. The kinetic energy $(KE)$ of the proton will be $....... \,eV$.

$A$ sphere of radius $1\,cm$ has a potential of $8000\,V$. The energy density near its surface will be:

The variation of electrostatic potential $V$ with radial distance $r$ from the centre of a positively charged metallic thin shell of radius $R$ is given by the graph:

If the electric potential of the inner shell of radius $a$ is $10\,V$ and that of the outer shell of radius $2a$ is $5\,V$,then the potential at the centre will be.....$V$