October 1954 Popular Electronics
[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Popular
Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged. See all articles from
timeless introduction for newcomers to electronics, this article in
the 1954 Popular Electronics presents the basics of what a capacitor
is and how it works.
What is a Capacitor?
A Primer on capacitors
capacitor-or electric condenser, as it was once known-is a device for
storing electrical energy and returning it as desired. It has storage
space - i.e., capacity for electricity; hence, capacitor.
a capacitor consists of two plates or systems of material that are capable
of conducting electricity, separated by an insulating material. The
oldest man-made capacitor of record is the Leyden jar, a glass bottle
whose inner and outer surfaces were covered with copper foil. Invented
in Holland in the mid-18th century, it was first used in America by
Benjamin Franklin in his classic experiments with natural lightning.
These Leyden Jar condensers and the glass plate condensers which succeeded
them were used in the early spark wireless sets.
capacitors usually use aluminum foil electrodes or plates, although
Invar steel, copper, and tantalum plates; lead, copper, and tantalum
foils; as well as thin zinc and silver films are in use for specialized
dielectric or insulating materials may be paper impregnated with an
oil or wax, electrolytically formed oxide films, plastic films, ceramics,
glass, air or a compressed gas.
The combination of electrodes
and dielectrics may be a rolled assembly such as the ordinary "tubular"
paper capacitor; a fixed or adjustable mechanical plate structure; a
disc or hollow tube; a stacked series of plates or wafers; or a series
of coaxial cylinders.
Capacitors are essential components in
electronic and electrical circuits. They are used everywhere in our
modern electrical life - on power lines, TV and radio sets, in automobiles,
in aircraft, in fluorescent lamps, electric refrigerators, air conditioners,
oil burners, etc., etc.
capacitor manufacturer alone - Sprague Electric Company - has made well
over a billion capacitors in the last 25 years. Where do they go? Well,
remember that a table model radio uses about 15 and a table model television
set about 115.
Among the basic uses of this important circuit
component are the suppression of sparks across contacts as in auto distributors
and fluorescent starters; filtering or bypassing unwanted radio and
TV signals; coupling electronic circuits together; tuning circuits;
reducing "waste" circulating currents by improving "power factor"; suppressing
radio and TV noise; supplying electrical energy for conversion to light
in "pulsed photographic lighting systems"; and "phase splitting" or
.changing the nature of alternating current electricity supplied to
motors used with various appliances.
This informative message
is No.1 of a Series contributed by Sprague, the world's largest manufacture
Write Sprague Products Co., N. Adams, Ma. , for complete