$\sigma$ is the uniform surface charge density of a thin spherical shell of radius $R$. The electric field at any point on the surface of the spherical shell is:

The expression for electric field intensity at a point outside a uniformly charged thin plane sheet is (where $d$ is the distance of the point from the plane sheet):

$A$ solid metallic sphere has a charge $+3Q$. Concentric with this sphere is a conducting spherical shell having charge $-Q$. The radius of the sphere is $a$ and that of the spherical shell is $b$ $(b > a)$. What is the electric field at a distance $R$ $(a < R < b)$ from the centre?

The electric field inside a spherical shell of uniform surface charge density is

The region between two concentric spheres of radii '$a$' and '$b$' (see figure) has a volume charge density $\rho = \frac{A}{r}$,where $A$ is a constant and $r$ is the distance from the centre. At the centre of the spheres is a point charge $Q$. The value of $A$ such that the electric field in the region between the spheres is constant,is:

If the uniform surface charge density on an infinite plane sheet is $\sigma$,the electric field near the surface will be . . . . . . .