When a dielectric material is placed between the plates of a capacitor, the molecules inside the
dielectric become polarized. Polarization is the alignment of electric dipoles (positive and
negative charges) within the dielectric due to the external electric field.
Process of Polarization:
Before applying an electric field, the molecules in the dielectric are randomly oriented. The
material is electrically neutral. When an external field Eo is applied, the negative charges in
each molecule shift slightly toward the positive plate, and the positive charges shift toward the
negative plate. This creates small electric dipoles within the dielectric. The alignment of these
dipoles produces an induced electric field Ei, which opposes the external field Eo. The total
field inside the capacitor is now reduced to E=Eo−Ei, meaning that the dielectric weakens the
overall field inside the capacitor. This polarization effect is why inserting a dielectric decreases
the electric field strength but increases capacitance.