An infinite line charge produces an electric field of $9 \times 10^6 \; N/C$ at a distance of $2 \; cm$. Calculate the linear charge density in $\mu C/m$.

Obtain an expression for the electric field at the surface of a charged conductor.

There is a solid sphere of radius $R$ having uniformly distributed charge throughout it. What is the relation between electric field $E$ and distance $r$ from the centre (where $r < R$)?

$A$ spherical shell with an inner radius $a$ and an outer radius $b$ is made of conducting material. $A$ point charge $+Q$ is placed at the centre of the spherical shell and a total charge $-q$ is placed on the shell. Find the final charge distribution on the surfaces.

$A$ solid metal sphere has a charge of $+3Q$. It is concentric with a conducting spherical shell having a charge of $-Q$. The radius of the sphere is $a$ and the radius of the shell is $b$ $(b > a)$. The electric field at a distance $R$ from the center $(a < R < b)$ is .......

The magnitude of electric field on the surface of a uniformly charged metallic spherical shell is $E$. If a hole is made in it using an insulating device,then the magnitude of electric field in the hole will be