Capacitor

A Polarised Capacitor’s plates are polarity sensitive and are normally electrolytic. The positive lead is shown on the schematic with a "+" symbol. The negative lead is generally not shown on the schematic, but may be marked on the capacitor with a bar or "-" symbol. Polarized capacitors are the electrolytic type or tandalium type. Polarized capacitors have large leakage current if the voltage is inverted.

The reason an electrolytic capacitor is polarized is due to the fact that the aluminum oxide layer is held in place by the electric field, and when reverse-biased, it dissolves into the electrolyte. Connecting an electrolytic capacitor backwards