The electric force acting between two point charges kept at a certain distance in vacuum is $16 \ N$. If the same two charges are kept at the same distance in a medium of dielectric constant $8$,the electric force acting between them is . . . . . . .

Can a metal be used as a medium for a dielectric?

Two charges placed in air repel each other by a force of $10^{-4} \ N$. When oil is introduced between the charges,the force becomes $2.5 \times 10^{-5} \ N$. The dielectric constant of oil is:

Polar molecules are the molecules:

With the rise in temperature,the dielectric constant $K$ of a liquid

$Assertion \; (A)$: Non-polar materials do not have any permanent dipole moment.
$Reason \; (R)$: When a non-polar material is placed in an electric field,the centre of the positive charge distribution of its individual atom or molecule coincides with the centre of the negative charge distribution.
In the light of the above statements,choose the most appropriate answer from the options given below: