Two charged spherical conductors of radius $R_{1}$ and $\mathrm{R}_{2}$ are connected by a wire. Then the ratio of surface charge densities of the spheres $\left(\sigma_{1} / \sigma_{2}\right)$ is :
$\frac{\mathrm{R}_{1}}{\mathrm{R}_{2}}$
$\frac{R_{2}}{R_{1}}$
$\sqrt{\left(\frac{\mathrm{R}_{1}}{\mathrm{R}_{2}}\right)}$
$\frac{\mathrm{R}_{1}^{2}}{\mathrm{R}_{2}^{2}}$
$64$ small drops of mercury, each of radius $ r$ and charge $q$ coalesce to form a big drop. The ratio of the surface density of charge of each small drop with that of the big drop is
Charges $Q, 2Q$ and $-Q$ are given to three concentric conducting shells $A, B$ and $C$ respectively as shown the ratio of charges on inner and outer surfaces of shell $C$ will be
A positive point charge $q$ is placed at a distance $2 R$ from the surface of a metallic shell of radius $R$. The electric field at centre of shell due to induced charge has magnitude
‘The interior of a conductor can have no excess charge in the static situation’. Explain.
‘At the surface of a charged conductor electrostatic field must be normal to the surface at every point’. Explain.