Electro-optics.
The branch of natural science treating of the relations between light
and electricity. Both are supposed to be phenomena of or due to the
luminiferous ether. To it may be referred the following:
(a) Electro-magnetic Stress and Magnetic Rotary Polarization;
(b) Dielectric Strain; all of which may be referred to in this book;
(c) Change in the resistance of a conductor by changes in light to which
it is exposed (see Selenium);
(d) The relation of the index of refraction of a dielectric to the
dielectric constant (see Electro-magnetic Theory of Light);
(e) The identity (approximate) of the velocity of light in centimeters
and the relative values of the electrostatic and electro-magnet units
of intensity, the latter being 30,000,000,000 times greater than the
former, while the velocity of light is 30,000,000,000 centimeters per
second.
Electrophoric Action.
The action of an electrophorous; utilized in influence machines. (See
Electrophorous.)
Fig. 159. ELECTROPHOROUS.
Electrophorous.
An apparatus for the production of electric charges of high potential by
electrostatic induction, q. v. It consists of a disc of insulating
material B, such as resin or gutta percha, which is held in a shallow
metal-lined box or form. The disc may be half an inch thick and a foot
or more in diameter, or may be much smaller and thinner. A metal disc A,
smaller in diameter is provided with an insulating handle which may be
of glass, or simply silk suspension strings. To use it the disc B is
excited by friction with a cat-skin or other suitable substance. The
metallic disc is then placed on the cake of resin exactly in its centre,
so that the latter disc or cake projects on all sides. Owing to
roughness there is little real electric contact between the metal and
dielectric. On touching the metal disc a quantity of negative
electricity escapes to the earth. On raising it from the cake it comes
off excited positively, and gives a spark and is discharged. It can be
replaced, touched, removed and another spark can be taken from it, and
so on as long as the cake stays charged.
The successive discharges represent electrical energy expended. This is
derived from the muscular energy expended by the operator in separating
the two discs when oppositely excited. As generally used it is therefore
an apparatus for converting muscular or mechanical energy into electric
energy.