In a uniformly charged sphere of total charge $Q$ and radius $R$, the electric field $E$ is plotted as function of distance from the centre of the sphere. The graph which would correspond to the above description will be

Electric charges $+q$ and $-q$ are placed at points $A$ and $B$ respectively which are at a distance of $2 L$ apart. If $C$ is the midpoint between $A$ and $B$, then the work done in moving a charge $+Q$ along the semi-circle $C R D$ is

Choose the incorrect statement.

In a regular polygon of 10 sides, each corner is at a distance $R$ from the centre. Identical charges are placed at 9 corners. At the centre, the magnitude of electric field is $E$ and the potential is $V$. The ratio $\frac{V}{E}$ is