Inserting different dielectric materials between the plates of a charged parallel plate capacitor while it is connected to an electroscope demonstrates the effect of dielectrics on capacitance. Each dielectric material increases the capacitance compared to air, which is shown by the increased deflection of the electroscope leaves. This highlights the role of dielectric constant in enhancing the storage capacity of a capacitor and the relationship between dielectric materials and electric field reduction within the capacitor.