The Standard Electrical Dictionary / A Popular Dictionary of Words and Terms Used in the Practice of Electrical Engineering

by T. O'Conor Sloane

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.
231 STANDARD ELECTRICAL DICTIONARY.
Electro-physiology.
The science of the electric phenomena of the animal system. It may also
be extended to include plants. The great discovery of Galvani with the
frog's body fell into this branch of science. The electric fishes,
gymnotus, etc., present intense phenomena in the same.
Electroplating.
The deposition by electrolysis of a coating of metal upon a conducting
surface. The simplest system makes the object to be plated the negative
electrode or plate in a galvanic couple. Thus a spoon or other object
may be connected by a wire to a plate of zinc. A porous cup is placed
inside a battery jar. The spoon is placed in the porous cup and the zinc
outside it. A solution of copper sulphate is placed in the porous cup,
and water with a little sodium or zinc sulphate dissolved in it,
outside. A current starts through the couple, and copper is deposited on
the spoon.
A less primitive way is to use a separate battery as the source of
current; to connect to the positive plate by a wire the object to be
plated, and a plate of copper, silver, nickel or other metal to the
other pole of the battery. On immersing both object and plate (anode) in
a bath of proper solution the object will become plated.
In general the anode is of the same material as the metal to be
deposited, and dissolving keeps up the strength of the bath. There are a
great many points of technicality involved which cannot be given here.
The surface of the immersed object must be conductive. If not a fine
wire network stretched over it will gradually fill up in the bath and
give a matrix. More generally the surface is made conductive by being
brushed over with plumbago. This may be followed by a dusting of iron
dust, followed by immersion in solution ot copper sulphate. This has the
effect of depositing metallic copper over the surface as a starter for
the final coat.
Attention must be paid to the perfect cleanliness of the objects, to the
condition of the bath, purity of anodes and current density.
Voltaic batteries are largely used for the current as well as special
low resistance dynamos. Thermo-electric batteries are also used to some
extent but not generally.
Electro-pneumatic Signals.
Signals, such as railroad signals or semaphores, moved by compressed
air, which is controlled by valves operated by electricity. The House
telegraph, which was worked by air controlled by electricity, might come
under this term, but it is always understood as applied to railroad
signals, or their equivalent.
232 STANDARD ELECTRICAL DICTIONARY.
Electropoion Fluid.
An acid depolarizing solution for use in zinc-carbon couples, such as
the Grenet battery. The following are formulae for its preparation:
(a) Dissolve one pound of potassium bichromate in ten pounds of water,
to which two and one-half pounds of concentrated sulphuric acid have
been gradually added. The better way is to use powdered potassium
bichromate, add it to the water first, and then gradually add the
sulphuric acid with constant stirring.
(b) To three pints of water add five fluid ounces of concentrated
sulphuric acid; add six ounces pulverized potassium bichromate.
(c) Mix one gallon concentrated sulphuric acid and three gallons of
water. In a separate vessel dissolve six pounds potassium bichromate in
two gallons of boiling water. Mix the two.
The last is the best formula. Always use electropoion fluid cold. (See
Trouvé's Solution--Poggendorff's Solution--Kakogey's Solution--
Tissandrier's Solution--Chutaux's Solution.)
Electro-positive. adj.
Appertaining to positive electrification; thus potassium is the most
electro-positive of the elements. (See Electro-negative.)
Electro-puncture.
The introduction into the system of a platinum point or needle,
insulated with vulcanite, except near its point, and connected as the
anode of a galvanic battery. The kathode is a metal one, covered with a
wet sponge and applied on the surface near the place of puncture. It is
used for treatment of aneurisms or diseased growths, and also for
removal of hair by electrolysis. (See Hair, Removal of by Electrolysis.)
Synonym--Galvano-puncture.
Electro-receptive. adj.
A term applied to any device or apparatus designed to receive and absorb
electric energy. A motor is an example of an electro-receptive
mechanism.
Electroscope.
An apparatus for indicating the presence of an electric charge, and also
for determining the sign, or whether the charge is positive or negative.
The simplest form consists of a thread doubled at its centre and hung
therefrom. On being charged, or on being connected to a charged body the
threads diverge. A pair of pith balls may be suspended in a similar way,
or a couple of strips of gold leaf within a flask (the gold leaf
electroscope). To use an electroscope to determine the sign of the
charge it is first slightly charged. The body to be tested is then
applied to the point of suspension, or other charging point. If at once
further repelled the charge of the body is of the same sign as the
slight charge first imparted to the electroscope leaves; the leaves as
they become more excited will at once diverge more. If of different sign
they will at first approach as their charge is neutralized and will
afterwards diverge.
The gold-leaf electroscope is generally enclosed in a glass bell jar or
flask. Sometimes a pair of posts rise, one on each side, to supply
points of induction from the earth to intensify the action. (See
Electrometer, Quadrant--Electroscope, Gold leaf, and others.)
233 STANDARD ELECTRICAL DICTIONARY.
Electroscope, Bennett's.
A gold-leaf electroscope, the suspended leaves of which are contained in
a glass shade or vessel of dry air. On the inside of the glass shade are
two strips of gold leaf, which rise from the lower edge a short
distance, being pasted to the glass, and connected to the ground. These
act by induction to increase the sensitiveness of the instruments.
Electroscope, Bohenberger's.
A condensing electroscope (see Electroscope, Condensing) with a single
strip of gold leaf suspended within the glass bell. This is at an equal
distance from the opposite poles of two dry piles (see Zamboni's Dry
Pile) standing on end, one on each side of it. As soon as the leaf is
excited it moves toward one and away from the other pile, and the sign
of its electrification is shown by the direction of its motion.
Electroscope, Condensing.
A gold leaf electroscope, the glass bell of which is surmounted by an
electrophorous or static condenser, to the lower plate of which the
leaves of gold are suspended or connected.
In use the object to be tested is touched to the lower plate, and the
upper plate at the same time is touched by the finger. The plates are
now separated. This reduces the capacity of the lower plate greatly and
its charge acquires sufficient potential to affect the leaves, although
the simple touching may not have affected them at all.
Electroscope, Gold Leaf.
An electroscope consisting of two leaves of gold leaf hung in contact
with each other from the end of a conductor. When excited they diverge.
The leaves are enclosed in a glass vessel.

Fig. 160. GOLD LEAF ELECTROSCOPE.
234 STANDARD ELECTRICAL DICTIONARY.
Electroscope, Pith Ball.
Two pith balls suspended at opposite ends of a silk thread doubled in
the middle. When charged with like electricity they repel each other.
The extent of their repulsion indicates the potential of their charge.
Electrostatic Attraction and Repulsion.
The attraction and repulsion of electrostatically charged bodies for
each other, shown when charged with electricity. If charged with
electricity of the same sign they repel each other. If with opposite
they attract each other. The classic attraction and subsequent repulsion
of bits of straw and chaff by the excited piece of amber is a case of
electrostatic attraction and repulsion. (See Electricity,
Static--Electrostatics--Coulomb's Laws of Electrostatic Attraction and
Repulsion.)
Electrostatic Induction, Coefficient of.
The coefficient expressing the ratio of the charge or change of charge
developed in one body to the potential of the inducing body.
Electrostatic Lines of Force.
Lines of force assumed to exist in an electrostatic field of force, and
to constitute the same. In general they correspond in action and
attributes with elcctro-magnetic lines of force. They involve in almost
all cases either a continuous circuit, or a termination at both ends in
oppositely charged surfaces.

Fig. 161. ELECTROSTATIC LINES OF FORCE
BETWEEN NEAR SURFACES.

Fig. 162. ELECTROSTATIC LINKS OF FORCE
BETWEEN DISTANT SURFACES.
235 STANDARD ELECTRICAL DICTIONARY.
The cut, Fig. 161, shows the general course taken by lines of force
between two excited surfaces when near together. Here most of them are
straight lines reaching straight across from surface to surface, while a
few of them arch across from near the edges, tending to spread. If the
bodies are drawn apart the spreading tendency increases and the
condition of things shown in the next cut, Fig. 162, obtains. There is
an axial line whose prolongations may be supposed to extend
indefinitely, as occupying a position of unstable equilibrium. Here the
existence of a straight and unterminated line of force may be assumed.
A direction is predicated to lines of force corresponding with the
direction of an electric current. They are assumed to start from a
positively charged and to go towards a negatively charged surface. A
positively charged body placed in an electrostatic field of force will
be repelled from the region of positive into or towards the region of
negative potential following the direction of the lines of force, not
moving transversely to them, and having no transverse component in its
motion.
[Transcriber's note: More precisely, "A positively charged body placed
in an electrostatic field of force will be repelled from the region of
positive into or towards the region of negative potential ACCELERATING
in the direction of the lines of force, not ACCELERATING transversely to
them, and having no transverse component in its ACCELERATION."
Previously acquired momentum can produce a transverse component of
VELOCITY.]
Electrostatics.
The division of electric science treating of the phenomena of electric
charge, or of electricity in repose, as contrasted with electro-dynamics
or electricity in motion or in current form. Charges of like sign repel,
and of unlike sign attract each other. The general inductive action is
explained by the use of the electrostatic field of force and
electrostatic lines of force, q. v. The force of attraction and
repulsion of small bodies or virtual points, which are near enough to
each other, vary as the square of the distance nearly, and with the
product of the quantities of the charges of the two bodies.
Electrostatic Refraction.
Dr. Kerr found that certain dielectrics exposed to electric strain by
being placed between two oppositely excited poles of a Holtz machine or
other source of very high tension possess double refracting powers, in
other words can rotate a beam of polarized light, or can develop two
complimentary beams from common light. Bisulphide of carbon shows the
phenomenon well, acting as glass would if the glass were stretched in
the direction of the electrostatic lines of force. To try it with glass,
holes are drilled in a plate and wires from an influence machine are
inserted therein. The discharge being maintained through the glass it
polarizes light.
Synonym--Kerr Effect.
Electrostatic Series.
A table of substances arranged in the order in which they are
electrostatically charged by contact, generally by rubbing against each
other. The following series is due to Faraday. The first members become
positively excited when rubbed with any of the following members, and
vice versa. The first elements correspond to the carbon plate in a
galvanic battery, the succeeding elements to the zinc plate.
Cat, and Bear-skin--Flannel--Ivory--Feathers--Rock Crystal--Flint
Glass--Cotton--Linen--Canvas--White Silk--the Hand--Wood--Shellac--the
Metals (Iron-Copper-Brass-Tin-Silver-Platinum)--Sulphur. There are some
irregularities. A feather lightly drawn over canvas is negatively
electrified; if drawn through folds pressed against it it is positively
excited. Many other exceptions exist, so that the table is of little
value.
236 STANDARD ELECTRICAL DICTIONARY.
Electrostatic Stress.
The stress produced upon a transparent medium in an electrostatic field
of force by which it acquires double refracting or polarizing properties
as regards the action of such medium upon light. (See Electrostatic
Refraction.)
Electro-therapeutics or Therapy.
The science treating of the effects of electricity upon the animal
system in the treatment and diagnosis of disease.
Electrotonus.
An altered condition of functional activity occurring in a nerve
subjected to the passage of an electric current. If the activity is
decreased, which occurs near the anode, the state is one of
anelectrotonus, if the activity is increased which occurs near the
kathode the condition is one of kathelectrotonus.
Electrotype.
The reproduction of a form of type or of an engraving or of the like by
electroplating, for printing purposes. The form of type is pressed upon
a surface of wax contained in a shallow box. The wax is mixed with
plumbago, and if necessary some more is dusted and brushed over its
surface and some iron dust is sprinkled over it also. A matrix or
impression of the type is thus obtained, on which copper is deposited by
electroplating, q. v.
Element, Chemical.
The original forms of matter that cannot be separated into constituents
by any known process. They are about seventy in number. Some of the
rarer ones are being added to or cancelled with the progress of chemical
discovery. For their electric relations see Electro-chemical
Equivalents--Electro-chemical Series.
The elements in entering into combination satisfy chemical affinity and
liberate energy, which may take the form of electric energy as in the
galvanic battery, or of heat energy, as in the combustion of carbon or
magnesium. Therefore an uncombined element is the seat of potential
energy. (See Energy, Potential.) In combining the elements always
combine in definite proportions. A series of numbers, one being proper
to each element which denote the smallest common multipliers of these
proportions, are called equivalents. Taking the theory of valency into
consideration the product of the equivalents by the valencies gives the
atomic weights.
237 STANDARD ELECTRICAL DICTIONARY.
Element, Mathematical.
A very small part of anything, corresponding in a general way to a
differential, as the element of a current.
Element of a Battery Cell.
The plates in a galvanic couple are termed elements, as the carbon and
zinc plates in a Bunsen cell. The plate unattacked by the solution, as
the carbon plate in the above battery, is termed the negative plate or
element; the one attacked, as the zinc plate, is termed the positive
plate or element.
Synonym--Voltaic Element.
Elements, Electrical Classification of.
This may refer to Electro-chemical Series, Electrostatic Series, or
Thermo-electric Series, all of which may be referred to.
Element, Thermo-electric.
One of the metals or other conductors making a thermo-electric couple,
the heating of whose junction produces electro-motive force and a
current, if on closed circuit. The elements of a couple are respectively
positive and negative, and most conductors can be arranged in a series
according to their relative polarity. (See Thermo-electric Series.)
Elongation.
The throw of the magnetic needle. (See Throw.)
Synonym--Throw.
Embosser, Telegraph.
A telegraphic receiver giving raised characters on a piece of paper. It
generally refers to an apparatus of the old Morse receiver type, one
using a dry point stylus, which pressing the paper into a groove in the
roller above the paper, gave raised characters in dots and lines.

Fig. 163. MORSE RECEIVER.
238 STANDARD ELECTRICAL DICTIONARY.
E. M. D. P.
Abbreviation for "electro-motive difference of potential" or for
electro-motive force producing a current as distinguished from mere
inert potential difference.
E. M. F.
Abbreviation for "electro-motive force."