A capacitor is an electrical device that can store electrical energy. In this way it is like a battery; however, unlike a battery, a capacitor has the property of capacitance, which is the ability to store electric charge and let it out all at once, and it can resist changes of voltage across its terminals. Capicatance is measures in units of farads, though typical capacitors have values of picofarads, one trillionth of a farad.

A capacitor consists of two conductors that are separated by a dielectric (insulator). The larger the surface area of the conductors and the smaller the separation between them, the larger the capacitance will be. There are two main types of capacitors--variable (which are tunable) and fixed (which have a single, fixed capacitance). Fixed capacitors, which comprise the lion's share of the market, come in two types: electrolytic and non-electrolytic.

The origin of the capacitor...