'X' is a substance which does not allow the flow of charges through it but permits them to exert electrostatic forces on one another through it. Identify X.

MCQs on electrostatic potential, potential due to point charge and electric dipole, equipotential surfaces, potential energy in external field, conductors electrostatics, dielectrics, polarisation, capacitors, capacitance, parallel plate capacitor, dielectric capacitance effects, capacitors combination and van de graff generator.