Capacitance is a property of electric circuits that describes how much electricity is stored between two plates or wires. It is defined as C=Q/V, where C stands for capacitance, Q for charge, and V for voltage.
Because of this inverse relationship, most capacitors are quite large compared to other parts on a circuit board, and still only power circuits in the range of a few microfarads. (The farad, named for Michael Faraday, is the unit of capacitance in the SI system.) Recently, by packing many curved plates into a single cylindrical capacitor, electronics companies have been able to shrink the volume of a capacitor by factors of two or three, thus producing a corresponding boost in farad capacity. It is now possible to buy capacitors as powerful as one or two farads, and super-small capacitors in the kilofarad (one thousand farads) range are being developed in Britain.
- IEC to develop standard for supercapacitors. EngineerLive, March 27, 2008.