Capacitor
A capacitor is a passive electronic component that stores energy in the form of
an electrostatic field. In its simplest form, a capacitor consists of two conducting
plates separated by an insulating material called the dielectric. The capacitance
is directly proportional to the surface areas of the plates, and is inversely
proportional to the separation between the plates.
Capacitance also depends on the dielectric constant of the substance separating
the plates.
The standard unit of capacitance is the farad, abbreviated F. This is a large
unit; more common units are the microfarad, abbreviated µF (1 µF =
10-6 F) and the picofarad, abbreviated pF (1 pF = 10-12 F).
Capacitors can be fabricated onto integrated circuit (IC) chips. They are commonly
used in conjunction with transistors in dynamic random access memory (DRAM).
The capacitors help maintain the contents of memory. Because of their tiny physical
size, these components have low capacitance. They must be recharged thousands
of times per second or the DRAM will lose its data.
Large capacitors are used in the power supplies of electronic equipment of
all types, including computers and their peripherals. In these systems, the
capacitors smooth out the rectified utility AC, providing pure, battery-like
DC.