Electrolytic Capacitor

Electrolytic Capacitor

An Electrolyte is obtained by passing a direct current between two sheets of aluminium foils (A and C) with a suitable electrolyte ammonium  borate between the foils. Due to electrolysis, a very thin film of thickness of the order of 10^-6 cm of aluminium oxide is formed on the anode plate and acts as the dielectric between the two plates. The electrolyte is a good conductor and hence along with C it forms the cathode. As the dielectric thickness d is very small the capacitance will be very high.

These are widely used when high capacitance are required .Capacitance of the order of 10³ μ F can be easily obtained with electrolyte capacitors of small volumes.
A Tantalum capacitor is a electrolytic capacitor consisting of pellet of tantalum metal as anode, covered by insulating layers and these act as dielectrics.

Care must be taken to connect this capacitor with proper polarity in a circuit. Otherwise the oxide film will breakdown. For this reason in an electrolyte capacitor the polarity of terminals will be indicated.