A charge of total amount $Q$ is distributed over two concentric hollow spheres of radii $r$ and $R ( R > r)$ such that the surface charge densities on the two spheres are equal. The electric potential at the common centre is
$\frac{1}{{4\pi {\varepsilon _0}}}\frac{{\left( {R - r} \right)Q}}{{\left( {{R^2} + {r^2}} \right)}}$
$\frac{1}{{4\pi {\varepsilon _0}}}\frac{{\left( {R + r} \right)Q}}{{2\left( {{R^3} + {r^3}} \right)}}$
$\frac{1}{{4\pi {\varepsilon _0}}}\frac{{\left( {R + r} \right)Q}}{{\left( {{R^2} + {r^2}} \right)}}$
$\frac{1}{{4\pi {\varepsilon _0}}}\frac{{\left( {R - r} \right)Q}}{{2\left( {{R^2} + {r^2}} \right)}}$
Four point charges $-Q, -q, 2q$ and $2Q$ are placed, one at each comer of the square. The relation between $Q$ and $q$ for which the potential at the centre of the square is zero is
Draw a graph for variation of potential $\mathrm{V}$ with distance $\mathrm{r}$ for a point charge $\mathrm{Q}$.
Two spheres $A$ and $B$ of radius $a$ and $b$ respectively are at same electric potential. The ratio of the surface charge densities of $A$ and $B$ is
The variation of electrostatic potential with radial distance $r$ from the centre of a positively charged metallic thin shell of radius $R$ is given by the graph
Two charged conducting spheres of radii $a$ and $b$ are connected to each other by a conducting wire. The ratio of charges of the two spheres respectively is: