The electric field between the two spheres of a charged spherical condenser

Two charges placed in air repel each other by a force of ${10^{ – 4}}\,N$. When oil is introduced between the charges, the force becomes $2.5 \times {10^{ – 5}}\,N$. The dielectric constant of oil is

Electric charges of $1\,\mu C,\, – 1\,\mu C$ and $2\,\mu C$ are placed in air at the corners $A$, $B$ and $C$ respectively of an equilateral triangle $ABC$ having length of each side $10 \,cm$. The resultant force on the charge at $C$ is……$N$

Three point charges are placed at the corners of an equilateral triangle. Assuming only electrostatic forces are acting

Given below are three schematic graphs of potential energy $V(r)$ versus distance $r$ for three atomic particles : electron $\left(e^{-}\right)$, proton $\left(p^{+}\right)$and neutron $(n)$, in the presence of a nucleus at the origin $O$. The radius of the nucleus is $r_0$. The scale on the $V$-axis may not be the same for all figures. The correct pairing of each graph with the corresponding atomic particle is