Capacitor
Capacitor
Modern capacitors, by a cm rule.
Type
Passive
Invented Ewald Georg von Kleist (October
1745)
Electronic symbol
A capacitor or condenser is a passive elec-
tronic component consisting of a pair of con-
ductors separated by a dielectric. When a
voltage potential difference exists between
the conductors, an electric field is present in
the dielectric. This field stores energy and
produces a mechanical force between the
plates. The effect is greatest between wide,
flat, parallel, narrowly separated conductors.
An ideal capacitor is characterized by a
single constant value, capacitance, which is
measured in farads. This is the ratio of the
electric charge on each conductor to the po-
tential difference between them. In practice,
the dielectric between the plates passes a
small amount of leakage current. The con-
ductors and leads introduce an equivalent
series resistance and the dielectric has an
electric field strength limit resulting in a
breakdown voltage.
The properties of capacitors in a circuit
may determine the resonant frequency and
quality factor of a resonant circuit, power dis-
sipation and operating frequency in a digital
logic circuit, energy capacity in a high-power
system, and many other important system
characteristics.
History
Battery of 4 Leyden jars in Museum Boer-
have, Leiden.
In October 1745, Ewald Georg von Kleist of
Pomerania in Germany found that charge
could be stored by connecting a generator by
a wire to a volume of water in a hand-held
glass jar. [1] Von Kleist’s hand and the water
acted as conductors and the jar as a dielec-
tric. Von Kleist found that after removing the
generator, touching the wire resulted in a
painful spark. In a letter describing the ex-
periment, he said "I would not take a second
shock for the kingdom of France."[2] The fol-
lowing year, the Dutch physicist Pieter van
Musschenbroek invented a similar capacitor,
which was named the Leyden jar, after the
University of Leyden where he worked.[3]
Daniel Gralath was the first to combine sev-
eral jars