• Most Capacitors have nonconducting material - a dielectric - between their plates.
• Dielectric materials increase the capacitance C of a capacitor; usually by several orders of magnitude compared to air filled capacitors.
• Dielectrics help keep the electrical plates separated with out electrical contact. This also allows the separation of the plates to be reduced and thus increasing the capacitance.
• When a dielectric is placed between the plates of a capacitor, the permittivity of the space between the capacitors change from that of empty space e_o to that of the dielectric material e.
• For practical reasons it is more useful to define and use dielectric constant k which is the ratio of e_o over e when determining the change in capacitance due to the presence of a dielectric.
• The Dielectric Strength is the maximum Electric Field that the material can withstand before the material breaks down as an insulator and permits current to flow through the material.

Effects of the Presence of Dielectric on Capacitors