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

by T. O'Conor Sloane

Fig. 298. SWITCH WITH RING CONTACTS.
474 STANDARD ELECTRICAL DICTIONARY.
Ring, Faraday.
A closed ring of iron used as the core of a transformer or induction
coil. The term is derived from Faraday's classic experiment with such an
apparatus when he produced a spark by induction in a secondary circuit.
Roaring.
A term applied to the noise sometimes produced in a voltaic arc, when
the electrodes are close together and a heavy current is passing.
Rocker.
In a dynamo the movable piece, mounted concentrically with the
commutator, and carrying the rocker-arms and brush-holders. By moving it
the brushes are adjusted for proper lead.
Rocker Arms.
The arms projecting from a rocker and each carrying one of the
brush-holders.
Roget's Spiral.
An experimental apparatus for illustrating the mutual attraction of
currents going in like direction. A cylindrical helix or spiral of wire
is suspended by one end. Its lower end just dips into a mercury cup. An
active circuit is connected, one terminal to the upper end, the other
terminal to the mercury cup, bringing the apparatus in series into the
circuit. The current as it passes causes the coil to shorten, each
spiral attracting its neighbors. This breaks the circuit by drawing the
lower end out of the mercury cup. The current being cut off the coils
cease to attract each other, and the end dips into the mercury cup
again. This closes the circuit, the coils again attract each other and
the same sequence follows and is repeated over and over again. A bright
spark is produced at each break of the mercury contact.
Rotation of Liquids, Electro-dynamic.
By passing a current through a liquid, such as dilute sulphuric acid, it
rotates if exposed to the induction of a current flowing at right angles
to it. The condition resolves itself into a liquid traversed by
horizontal currents from centre to circumference or vice versa, rotated
by a current passing through a circular conductor below it.
475 STANDARD ELECTRICAL DICTIONARY.
Rotation of Liquids, Electro-magnetic.
The rotation produced in a liquid carrying centripetal or centrifugal
currents by an electromagnet. It is practically an intensification of
electro-dynamic rotation. (See Rotation of Liquids, Electro-dynamic.)
Rubber.
In a frictional electric machine the cushion of leather which is pressed
against the plate as it rotates.

475 STANDARD ELECTRICAL DICTIONARY.
S.
(a) Symbol for second.
(b) Symbol for space, or length; L is preferable.
(c) Symbol for south-seeking pole of a magnet.
Saddle Bracket.
A bracket carried on the top of telegraph poles, carrying an insulator
for the upper wire.
Safety Device.
(a) A device to prevent overheating of any portion of a circuit by
excess of current. It generally consists of a slip of fusible metal
which if the current attains too much strength melts and opens the
circuit. To ensure its breaking a weight is sometimes suspended from the
strip. In one form an insulated German silver wire is wrapped around the
end of the fusible strip a number of times and its end is connected to
it. The other end of the German silver wire connects with the main lead,
so that all the current goes through both in series. If the German
silver wire becomes heated from excess of current the coil wrapped
tightly around the end of the fusible strip melts it and opens the
circuit.
(b) Lightning arresters, q. v., may be cited under this heading.
Synonyms--Automatic Cut Out--Safety Fuse, Plug, or Strip.

Fig. 299. COCKBURN SAFETY FUSE.
Safety Fuse.
A strip of metal inserted so as to form part of a circuit and of such
size that a smaller current [than] would heat the regular wire of the
circuit dangerously, so as to cause a conflagration for instance, would
melt the fuse and open the circuit. As it sometimes happens that a
safety fuse melts without parting a weight is sometimes hung upon it, so
as to break it as it softens.
Salt.
A salt is a chemical compound containing two atoms of two radicals,.
which saturate each other. One atom or radical is electro-positive
referred to the other, which is electro-negative. By electrolysis salts
are decomposed, the atoms or radicals separating and uniting to form new
molecules.
476 STANDARD ELECTRICAL DICTIONARY.
Saturated. adj.
A liquid is saturated with a substance when it has dissolved all that it
can, while an excess is present in the liquid. It is possible, by
dissolving some salts in hot water and allowing the solution to cool
without access of air, to obtain a supersaturated solution. On
introduction of a crystal of the salt, or often on mere access of air,
the solution forms crystals and the liquid left is saturated.
Saw, Electric.
A platinum coated steel wire mounted and connected to be raised to
incandescence for cutting purposes.
Schweigger's Multiplier.
An old term for the galvanometer as invented by Schweigger soon after
Oerstedt's discovery.
Scratch Brushes.
Brushes for cleaning the surface of articles to be electroplated to give
a good metallic surface suitable for deposition. They have often wire
instead of bristles.
477 STANDARD ELECTRICAL DICTIONARY.

Fig. 300. WIRE GAUZE ELECTRIC SCREEN.
Screen, Electric.
A large plate or a hollow case or cage of conducting material connected
with the earth, and used to protect any body placed within it from
electrostatic influences.
If within a hollow conducting sphere an electrified body is placed, the
inner surface of the sphere will be charged with electricity of opposite
kind to that of the sphere, and the outer surface with the same kind as
that of the sphere. Thus the sum of the electricities called into action
by induction is zero. The two inner charges are bound to each other. The
induced charge on the outer surface of the sphere is all that has any
effect on objects in the outer air.
If the outer surface is connected to the earth it becomes discharged,
and however highly electrified the body introduced into the sphere and
the inner surface of such sphere may be, they produce no external
effects, as they are bound one to the other.
If the sphere is connected to the earth and an unelectrified object is
placed within it, such object will be perfectly shielded from the
effects of an outer electrostatic field. Perforated tinfoil or wire
gauze has just as good a result. A large plate of metal connected to the
earth has the same effect. The screen whether plane or hollow simply
retains a bound charge due to the field of force, thereby neutralizing
it, and the electricity of the opposite sign escapes to the earth. Thus
a true shielding or screening effect is produced.
In the cut an experiment is shown in which an electric screen is carried
by a Leyden jar. Pith balls are suspended outside and inside of it. By
the approach of an electrified body the outer pith balls will diverge,
while no effect is produced upon the inner ones.
Secondary Actions.
In electrolysis the direct products of the electrical decomposition are
not always obtained at the electrodes, but products due to their
reaction on the water and other chemicals may appear. These constitute
secondary actions. Thus if a solution of copper sulphate is electrolyzed
with platinum electrodes, metallic copper appears at one pole and
sulphuric acid and oxygen gas at the other. But the products of
electrolysis by the current are copper (Cu) and sulphion (SO4). The
latter reacting on water sets free oxygen gas and forms sulphuric acid.
The latter is a secondary action.
Secondary Generator.
(a) An alternating current converter generating a so-called secondary
current.
(b) A secondary battery, q. v., may be thus termed.
Secondary, Movable.
The term movable secondaries has been applied to rings, spheres and
discs of conducting material, such as copper, whose behavior when near
the pole of an electro-magnet traversed by an alternating current, have
been studied by Elihu Thomson. Such masses are subjected to very
peculiar movements and mutual reactions. As the phenomena are due to
induced currents the above term has been applied to the masses in which
the currents are induced.
478 STANDARD ELECTRICAL DICTIONARY.
Secondary Plates, Colors of.
In a secondary battery of the lead plate type, the color of the plates
is a good indication of the condition of the battery. The negative plate
should be brown or deep-reddish, the other should be slate-colored.
Secondary Poles.
Poles sometimes found in magnets existing in positions intermediate
between the end or true poles.
Synonym--Consequent Poles.
Seebeck Effect.
The production of a current by heating the junction of two different
metals forming part of a circuit, or the thermo-electric production of
current, is stated as the Seebeck effect, having been discovered by that
investigator.
Selenium.
A non-metallic element. It is interesting electrically on account of the
changes its electric resistance undergoes when it is subjected to light.
In one set of experiments it was found that diffused light caused the
resistance to fall in the ratio of 11 to 9. Full sunlight reduced it to
one-half. Of the spectrum colors red was most powerful and the ultra red
region still more strongly affected its resistance.
The effect produced by exposure to light is instantaneous, but on
removal to the dark only slowly disappears.
A vessel of hot water was found to have no effect, showing that short
ether waves are essential to the effect.
Selenium Cell.
A selenium resistance box. Vitreous selenium is made by keeping ordinary
selenium for some hours at a temperature of about 220º C. (428º F.)
after fusing. It is placed in an electric circuit as part of the
conductor.
Its resistance can then be determined. It decreases in sunlight to about
one-half its resistance in the dark.
The selenium cell is used in the Photophone, q. v. Otherwise it is
little more than a subject of experiment.
Selenium Eye.
A model eye in which selenium in circuit with a battery and galvanometer
takes the place of the retina of the human eye.
Self-repulsion.
When a body is electrified each molecule repels its neighbor and the
condition in question is thus designated. An electrified soap-bubble
expands in virtue of self-repulsion.
Semi-conductors.
Substances which conduct static electricity poorly, but quite
appreciably and beyond the extent of leakage. The following are
examples: Alcohol and ether, powdered glass, flowers of sulphur, dry
wood, paper, ice at 0º C. (32º F.)
479 STANDARD ELECTRICAL DICTIONARY.
Sensibility.
The measure of the effect of a current upon a galvanometer,
or any similar case.
Sensitiveness, Angle of Maximum.
Every galvanometer has its angle of maximum sensitiveness, which is the
angle of deflection at which a small increment of current will produce
the greatest deflection. For every tangent galvanometer 45° is the angle
in question. In using a galvanometer for direct reading methods it is an
object to have it work at its angle of maximum sensitiveness.
Separately Excited Dynamo.
A dynamo-electric machine whose field magnet is excited from an outside
source, which may be another dynamo or a battery. Alternating current
dynamos are often of this description.
Separate Touch.
In magnetism a method of inducing magnetism in a steel bar. The opposite
poles of two magnets are applied at the center of the bar to be
magnetized, but without touching each other, and are drawn apart to its
ends. They are returned through the air and the process is repeated a
number of times and on both sides of the bar if necessary.
Separation of Electricities.
Under the double fluid theory of electricity the action of
electrification in accumulating positive electricity in one conductor
and negative on the other of the excited surfaces of two conductors.
Separator.
India rubber bands or other forms used in batteries to keep the plates
from touching in the cell; especially applied to secondary batteries,
where the plates are so near together as to require separators to
prevent short circuiting.

Fig. 301. SERIES CONNECTION.
Series.
(a) Arranged in succession as opposed to parallel. Thus if a set of
battery jars are arranged with the zinc of one connected to the carbon
of the next one for the entire number, it is said to be arranged in
series. When incandescent lamps are arranged in succession so that the
current goes through one after the other they are arranged in series.
The opposite of parallel, q. v., or multiple arc, q. v.; it may be used
as a noun or as an adjective.
(b) See Electro-Chemical Series;
(c) Thermo-Electric Series
(d) Electrostatic Series;
(e) Electro-motive Series.
Synonym--Cascade Connection (but little used.)
480 STANDARD ELECTRICAL DICTIONARY.
Series-multiple.
Arrangement of electric apparatus, in which the parts are grouped in
sets in parallel and these sets are connected in series. It is used as a
noun, as "arranged in series-multiple," or as an adjective, as "a
series-multiple circuit or system."

Fig. 302. SERIES-MULTIPLE CONNECTION.
Service Conductors.
In electric distribution the equivalents of service pipes in the
distribution of gas; wires leading from the street mains to the houses,
where current is to be supplied.
Serving.
The wrapping or winding of a cable composed of small size wire, laid
closely and smoothly with a tool called a serving mallet, or serving
block, or by machinery. It serves to protect the cable from wear.
Shackle.
In telegraph lines a swinging insulator bracket for use where wires make
an angle with the pole. A journal box is attached to the pole, like half
of a gate hinge. To this a short iron arm is pivoted so as to be free to
swing through a considerable angle. At its end an insulator is carried
to which the wire is attached. The shackle swings into line with the
wire, or takes a position for two wires corresponding to the resultant
of their directions of pull.