Electrolytic capacitors are capacitors in which one or both of the “plates” is a non-metallic conductive substance,an electrolyte.Electrolytes have lower conductivity than metals,so are only used in capacitors when metallic plate is not practical,such as when the dielectric surface is fragile or rough in shape or when ionic current is required to maintain the dielectric integrity.The flow of current causes an insulating metal oxide to grow out of and into the surface of the anode.The thickness,structure and composition of the insulating layer determine its dielectric strength.The applied potential between the anode metal and the bath cathode must be above the oxide breakdown voltage before significant current will flow.As current flows,the breakdown strength (formed voltage) and oxide thickness increase.The “electrolytic capacitors”are quite different from,and not to be confused with the “electrochemical capacitors” (also called ultracapacitors) the operation of which is based on the electrical double layer capacitance.