If the relative permittivity for any substance is $80$,then its electric susceptibility is . . . . . . .

The dielectric constant of pure water is $81$. Its permittivity will be ........

$A$ dielectric slab of dielectric constant $K$ is placed between the plates of a parallel plate capacitor carrying charge $q$. The induced charge $q^{\prime}$ on the surface of the slab is given by

$A$ cube of side $1 \ cm$ contains $100$ molecules,each having an induced dipole moment of $0.2 \times 10^{-6} \ C \cdot m$ in an external electric field of $4 \ N \cdot C^{-1}$. The electric susceptibility of the material is .... $C^2 \cdot N^{-1} \cdot m^{-2}$.

If the dielectric constant and dielectric strength are denoted by $k$ and $x$ respectively,then a material suitable for use as a dielectric in a capacitor must have

The dielectric strength of air is . . . . . . .