Faraday Found, in
1837, if introduced an insolating material in a capacitor the capacitance increased by a numerical factor K, which he called the dielectric constant of the insulating material.
Another effect of the introduction of a dielectric is to limit the potential difference that
can be applied
between the plates to a certain value Vmax, called
the breakdown
potential. If this
value is
substantially exceeded, the dielectric material will break down and form a conducting path between the plates. Every dielectric
material has a
characteristic dielectric
strength, which is the maximum value of the electric field
that it can tolerate
without breakdown.