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

by T. O'Conor Sloane

Fig. 303. DOUBLE SHACKLE
Shadow. Electric.
A term applied to a phenomenon of high vacua. If an electric discharge
is maintained in a Crookes' tube the glass opposite the negative
electrode tends to phosphoresce. A plate of aluminum, used also as the
positive electrode, protects the glass directly behind it so as to
produce the effect of a shadow.
Synonym--Molecular Shadow.
[Transcriber's note: The effect is due to the "shadowing" of the
electrons streaming past the plate.]
481 STANDARD ELECTRICAL DICTIONARY.
Sheath for Magnet Coils.
In 1867 C. E. Varley proposed the use of a copper sheath surrounding a
magnet core to diminish self-induction. It has since been used by Brush
and others. Sometimes metallic foil is laid between the successive coils
of wire.
Synonym--Mutual Induction Protector.
Sheath for Transformers.
A protective sheath of copper, interposed between the primary and
secondary circuits of an alternating current transformer. It is
connected to the earth. If the primary coil loses its insulation before
it can leak to the secondary it is grounded. This protects the secondary
circuit from the high electro-motive force of the primary circuit.
Shellac.
A resin; produced as an exudation upon the branches of certain Asiatic
trees, such as the banyan (Ficus religiosa). It is due to punctures in
the bark of the trees in question, which punctures are made by the
female of the insect coccus ficus or c. lacca.
Commercial shellac contains about 90 per cent. of resinous material, the
rest is made up of wax, gluten, coloring matter and other substances.
Shellac is soluble in alcohol, and in aqueous solutions of ammonium
chloride, of borax and in strong ammonia solution. Long standing is
required in the case of the last named solvent. Dilute hydrochloric and
acetic acids dissolve it readily; nitric acid slowly; strong sulphuric
acid is without action on it. Alkalies dissolve it.
In electric work it is used as an insulator and dielectric. Its
alcoholic solution is used to varnish glass plates of influence
machines, for the coils of induction coils and similar purposes.
Resistance in ohms per centimeter cube at 28° C. (82.4 F.)--(Ayrton),
9.0E15
Specific Inductive Capacity (Wüllner), 2.95 to 3.73
The same substance in less pure forms occurs in commerce, as stick lac,
lump lac, seed lac, button lac.
Shellac Varnish.
Solution of shellac in alcohol; methylic alcohol (wood alcohol or wood
naphtha) is often used as solvent.
Dr. Muirhead recommends button lac, dissolved in absolute alcohol, and
the top layers decanted. For highest insulation he dissolves the lac in
ordinary alcohol, precipitates by dropping into water, collects the
precipitate, dries and dissolves in absolute alcohol.
Shielded. adj.
An electric measuring instrument of the galvanometer type is shielded
when it is so constructed that its indications are not seriously
affected by the presence of neighboring magnets or by fields of force.
Shielding can be effected by using a very strong permanent magnet to
produce a field within which the magnetic needle moves and which reacts
upon it, or by enclosing the instrument in a thick iron box.
482 STANDARD ELECTRICAL DICTIONARY.
S. H. M.
Symbol or abbreviation for "simple harmonic motion."
Shock, Break.
A term in electro-therapeutics; the shock received when an electric
circuit, including the patient in series, is broken or opened.
Synonym--Opening Shock.
Shock, Electric.
The effect upon the animal system of the discharge through it of
electricity with high potential difference. Pain, nervous shock, violent
muscular contortions accompany it. Of currents, an alternating current
is reputed worse than a direct current; intermediate is the pulsatory
current.
The voltage is the main element of shock, amperage has also some direct
influence.
Shock, Static.
A term in electro-therapeutics. The application of static discharges
from small condensers or Leyden jars to a patient who is insulated from
the ground with one electrode applied to the conducting surface on which
he rests, while the other, a spherical electrode, is brought near the
body so as to produce a disruptive or spark discharge.
Short Circuit.
A connection between two parts of a circuit, which connection is of low
resistance compared to the intercepted portion. The term is used also as
a verb, as "to short circuit a lamp."

Fig. 304. DIAGRAM ILLUSTRATING SHORT CIRCUIT WORKING.
Short Circuit Working.
A method of working intermittently an electro-magnet so as to avoid
sparking. It consists in providing a short circuit in parallel with the
magnetic coils. This short circuit is of very low resistance. To throw
the magnet into action the short circuit is opened; to throw it out of
action the short circuit is closed. The shunt or short circuit must be
of negligibly small resistance and inductance.
483 STANDARD ELECTRICAL DICTIONARY.
Shovel Electrodes.
Large plate electrodes used in a medical bipolar bath. (See Bath,
Bipolar.)
Shunt.
In a current circuit a connection in parallel with a portion of the
circuit. Thus in a dynamo a special winding for the field may have its
ends connected to the bushes, from which the regular external circuit
also starts. The field is then wound in shunt with the armature. In the
case of a galvanometer a resistance coil may be put in parallel with it
to prevent too much current going through the galvanometer; this
connection is a shunt.
The word is used as a noun, as "a shunt," or "a connection or apparatus
in shunt with another," and as an adjective, as "a shunt connection," or
as a verb, as "to shunt a battery."
Shunt Box.
A resistance box designed for use as a galvanometer shunt. (See Shunt,
Galvanometer.) The box contains a series of resistance coils which can
be plugged in or out as required.
Shunt, Electro-magnetic.
In telegraphy a shunt for the receiving relay consisting of the coils of
an electro-magnet. It is placed in parallel with the relay. Its poles
are permanently connected by an armature. Thus it has high
self-induction.
On opening and closing the circuit by the sending key, extra currents
are produced in the shunt. The connections are so arranged that on
making the circuit the extra current goes through the relay in the same
direction as the principal current, while on breaking the circuit the
induced current goes in the opposite direction.
Thus the extra currents accelerate the production and also the cessation
of signalling currents, tending to facilitate the operations of sending
despatches.
Shunt, Galvanometer.
A resistance placed in parallel with a galvanometer, so as to short
circuit its coils and prevent enough current passing through it to
injure it. By knowing the resistance of the shunt and of the
galvanometer coils, the proportion of current affecting the galvanometer
is known. This gives the requisite factor for calculation. (See
Multiplying Power of Shunt.)
Shunt Ratio.
The coefficient expressing the ratio existing between the current in a
shunt and in the apparatus or conductor in parallel with it. (See
Multiplying Power of/ Shunt.)
Shunt Winding.
A dynamo or motor is shunt-wound when the field magnet winding is in
shunt or in parallel with the winding of the armature.
Shuttle Current.
A current alternating in direction; an alternating current.
484 STANDARD ELECTRICAL DICTIONARY.
Side-Flash.
A bright flashing lateral discharge from a conductor conveying a current
due to a static discharge.
Sighted Position.
In an absolute electrometer (see Electrometer, Absolute) the position of
the balanced arm carrying the movable disc or plate, when the disc and
guard plate are in one plane. The cross-hair on the lever-end is then
seen midway between two stops, or some other equivalent position is
reached which is discerned by sighting through a magnifying glass or
telescope.
Silver.
A metal; one of the elements; symbol Ag.; atomic weight, 108; valency, 1;
equivalent, 108; specific gravity, 10.5. It is a conductor of electricity.
Relative resistance, annealed, 1.0
Specific Resistance, annealed, at 0° C. (32° F.) 1.504 microhms.
Resistance of a wire at 0° C. (32° F.), Annealed. Hard Drawn.
(a) 1 foot long, weighing 1 grain, .2190 ohms .2389 ohms.
(b) 1 foot long, 1/1000 inch thick, 9.048 " 9.826 "
(c) 1 meter long, weighing 1 gram, .1527 " .1662 "
(d) 1 meter long, 1 millimeter thick, .01916 " .02080 "
Resistance annealed of a 1-inch cube, at 0° C. (32°F.) .5921 microhms.
Percentage increase in resistance per degree C.
(1.8 F.) at about 20° C. (68° F.), annealed, 0.377 per cent.
Electro-chemical equivalent, (Hydrogen = .0105) .1134 mgs.
Silver Bath.
A solution of a salt of silver for deposition in the electroplating
process.
The following is a typical formula:
Water, 10.0 parts by weight.
Potassium Cyanide, 5 " "
Metallic Silver, 2.5 " "
The silver is first dissolved as nitrate and converted into cyanide and
added in that form, or for 2.5 parts metallic silver we may read:
Silver cyanide, 3 parts by weight.
While many other formulas have been published the above is
representative of the majority. Other solvents for the silver than
potassium cyanide have been suggested, such as sodium hyposulphite, but
the cyanide solution remains the standard.
Silver Stripping Bath.
Various baths are used to remove silver from old electroplated articles.
Their composition depends upon the base on which the metal is deposited.
Silvered iron articles are placed as anodes in a solution of 1 part
potassium cyanide in 20 parts of water. As kathode a silver anode or a
copper one lightly oiled may be used. From the latter the silver easily
rubs off. For copper articles a mixture of fuming sulphuric acid and
nitric acid (40º Beaumé) may be used. The presence of any water in this
mixture will bring about the solution of the copper. Or fuming sulphuric
acid may be heated to between 300º and 400º F., some pinches of dry
pulverized potassium nitrate may be thrown in and the articles at once
dipped. These methods effect the solution of the silver, leaving the
copper unattacked.
485 STANDARD ELECTRICAL DICTIONARY.
Simple Substitution.
A method of obtaining a resistance equal to that of a standard. The
standard is put in circuit with a galvanometer and the deflection is
noted. For the standard another wire is substituted and its length
altered until the same deflection is produced. The two resistances are
then evidently identical. The standard can be again substituted to
confirm the result.
Sine Curve.
If we imagine a point moved back and forth synchronously with a
pendulum, and if such point made a mark upon paper, it would trace the
same line over and over again. If now the paper were drawn steadily
along at right angles to the line of motion of the point, then the point
would trace upon it a line like the profile of a wave. Such line is a
sine curve. It derives its name from the following construction. Let a
straight line be drawn, and laid off in fractions, such as degrees, of
the perimeter of a circle of given diameter. Then on each division of
the line let a perpendicular be erected equal in height to the sine of
the angle of the circle corresponding to that division; then if the
extremities of such lines be united by a curve such curve will be a sine
curve.
In such a curve the abscissas are proportional to the times, while the
ordinates are proportional to the sines of angles, which angles are
themselves proportional to the times. The ordinates pass through
positive and negative values alternately, while the abscissas are always
positive.
Any number of sine curves can be constructed by varying the diameter of
the original circle, or by giving to the abscissas a value which is a
multiple of the true length of the divisions of circle. If the pendulum
method of construction were used this would be attained by giving a
greater or less velocity to the paper as drawn under the pendulum.
A species of equation for the curve is given as follows: y = sin( x )
In this x really indicates the arc whose length is x, and reference
should be made to the value of the radius of the circle from which the
curve is described. It will also be noticed that the equation only
covers the case in which the true divisions of the circle are laid off
on the line. If a multiple of such divisions are used, say n times, or
1-n times, then the equation should read
y = n sin( x ) or y = sin( x ) / n
Synonyms--Curve of Sines--Sinusoidal Curve--Harmonic Curve.
486 STANDARD ELECTRICAL DICTIONARY.
Sine Law.
The force acting on a body is directly proportional to the sine of the
angle of deflection when--
I. The controlling force is constant in magnitude and direction; and
II. The deflecting force, although variable in its direction in space,
is fixed in direction relatively to the deflecting body.
Single Fluid Theory.
A theory of electricity. Electricity, as has been said, being
conveniently treated as a fluid or fluids, the single fluid theory
attributes electrical phenomena to the presence or absence of a single
fluid. The fluid repels itself but attracts matter; an excess creates
positive, a deficiency, negative electrification; friction, contact
action or other generating cause altering the distribution creates
potential difference or electrification. The assumed direction (see
Direction) of the current and of lines of force are based on the single
fluid theory. Like the double fluid theory, q. v., it is merely a
convenience and not the expression of a truth. (See Fluid, Electric, and
Double Fluid Theory.)
Synonym--Franklin's Theory.
Single Fluid Voltaic Cell.
A galvanic couple using only a single fluid, such as the Smee or Volta
cell.
Simple Harmonic Motion.
Motion of a point or body back and forth along a line; the motion of a
pendulum, as regards its successive swings back and forth, is an example
of harmonic motion.
Sinistrotorsal. adj.
The reverse of dextrotorsal, q. v. A helix with left-handed winding, the
reverse of an ordinary screw, such as a wood-screw or corkscrew.
Skin Effect.
A current of very brief duration does not penetrate the mass of a
conductor. Alternating currents for this reason are mainly conducted by
the outer layers of a conductor. The above is sometimes called the skin
effect.
Sled.
A contact for electric cars of the conduit system. It is identical with
the plow, q.v., but is drawn after the cars instead of being pushed
along with them.
Slide Meter Bridge.
A name for a Slide Bridge one meter long. There are also slide half
meter and slide quarter meter bridges and others. (See Meter Bridge.)
S. N. Code.
Abbreviation for single needle code, the telegraphic alphabet used with
the single needle system.
Soaking-in-and-out.
A term for the phenomena of the residual electrostatic charge; the
gradual acquirement or loss by a condenser of a portion of its
electrostatic charge.
487 STANDARD ELECTRICAL DICTIONARY.
Soldering, Electric.
(a) Soldering in which the solder is melted by means of electricity;
either current incandescence or the voltaic arc may be used. It is
identical in general with electric welding. (See Welding, Electric.)
(b) The deposition by electric plating of a metal over the ends of two
conductors held in contact. This secures them as if by soldering. It is
used in connecting the carbon filament of an incandescent lamp with the
platinum wires that pass through the glass. Copper is the metal usually
deposited.
Solenoid.
The ideal solenoid is a system of circular currents of uniform
direction, equal, parallel, of equal diameter of circle, and with their
centers lying on the same straight line, which line is perpendicular to
their planes.

Fig. 305. EXPERIMENTAL SOLENOID.
The simple solenoid as constructed of wire, is a helical coil, of
uniform diameter, so as to represent a cylinder. After completing the
coil one end of the wire is bent back and carried through the centre of
the coil, bringing thus both ends out at the same end. The object of
doing this is to cause this straight return member to neutralize the
longitudinal component of the helical turns. This it does approximately
so as to cause the solenoid for its practical action to correspond with
the ideal solenoid.
Instead of carrying one end of the wire through the centre of the coil
as just described, both ends may be bent back and brought together at
the centre.
A solenoid should always have this neutralization of the longitudinal
component of the helices provided for; otherwise it is not a true
solenoid.
Solenoids are used in experiments to represent magnets and to study and
illustrate their laws. When a current goes through them they acquire
polarity, attract iron, develop lines of force and act in general like
magnets.
A solenoid is also defined as a coil of insulated wire whose length is
not small as compared with its diameter.
488 STANDARD ELECTRICAL DICTIONARY.
Sonometer, Hughes'.
A sound measurer; a modification of a portion of Hughes' induction
balance, used for testing the delicacy of the ear or for determining the
relative intensity of sounds. (See Hughes' Induction Balance.) It is the
arrangement of three coils, two mounted one at each of the ends of a
graduated bar, and the third one between them and free to slide back and
forth thereon.
Sonorescence.
The property of producing sounds under the influence of momentary light
radiations rapidly succeeding each other. It is the property utilized in
the photophone, q. v.

Fig. 306. MORSE SOUNDER.
Sounder.
In telegraphy an instrument consisting of an electromagnet with armature
attached to an oscillating bar, the range of whose movements is
restricted by adjusting screws. The armature is drawn away from the
magnet by a spring. When a current is sent through the magnet the
armature is drawn towards the poles and produces a sound as the bar
strikes a striking piece or second adjusting screw. When the current
ceases the bar and armature are drawn back, striking the first mentioned
screw with a distinct sound, the back stroke.
The sounder is used to receive Morse and analogous character messages.
The forward strokes correspond to the beginnings of the dots or dashes
of the code, the back strokes to beginnings of the intervals. The
distinction between dots and dashes is made by observing the interval
between forward and back stroke.
Various devices are used to increase the sound. Sometimes a resonance
box is used on which the sounder is mounted.
In practice sounders are generally placed on local circuits and are
actuated by relays.
489 STANDARD ELECTRICAL DICTIONARY.
Sound Reading.
The art or method of receiving telegraph messages by ear. It is now
universally used by all expert Morse operators. It can only be applied
to telegraph systems producing audible sounds; in some cases, as in
needle telegraphy, it may be quite inapplicable.
Space, Clearance.
The space between faces of the pole pieces and the surface of the
armature in a dynamo. It is really the air gap, but in calculating
dynamo dimensions the thickness of the insulated copper wire windings of
the commutator are counted in as part of the air gap, because copper is
almost the same as air in impermeability. Clearance space is a
mechanical factor; the air gap is an electric or magnetic factor.
Synonym--Inter-air Space.
Space, Crookes' Dark.
In an exhausted tube, through which an electric discharge is caused to
pass, the space surrounding the negative electrode of the tube. This
space is free from any luminous effect, and by contrast with the light
of the discharge appears dark. The vacuum may be made so high that the
dark space fills the whole space between the electrodes. It is less for
a less vacuum and varies for other factors, such as the temperature of
the negative electrode from which it originates, the kind of residual
gas present, and the quality of the spark.
Space, Faraday's Dark.
The space in an exhausted tube between the luminous glows about the two
electrodes.
Space, Interferric.
A term for the air-gap in a magnetic circuit. It is etymologically more
correct than air-gap, for the latter is often two-thirds or more filled
with the insulating material and copper wire of the armature windings.
(See Space, Clearance.)
Spark Arrester.
A screen of wire netting fitting around the carbons of an arc lamp above
the globe to prevent the escape of sparks from the carbons.
Spark Coil.
A coil for producing a spark from a source of comparatively low
electro-motive force. It consists of insulated wire wound round a core
of soft iron, best a bundle of short pieces of wire. Such a coil may be
eight inches long and three inches thick, and made of No. 18-20 copper
wire, with a core one inch in diameter. On connecting a battery
therewith and opening or closing the circuit, a spark is produced by
self-induction, q. v. It is used for lighting gas.
490 STANDARD ELECTRICAL DICTIONARY.
Spark, Duration of Electric.
Wheatstone determined the duration of the spark given by a Leyden jar as
1/24000 second. Feddersen by interposing a tube of water 9 millimeters
(.36 inch) long in its path found that it lasted 14/10000 second, and
with one 180 millimeters (7.2 inches) long, 188/10000 second. Lucas and
Cazin for a 5 millimeter (.2 inch) spark, with different numbers of
Leyden jars, found the following:
Number of jars. Duration of Spark.
2 .000026 second
4 .000041 "
6 .000045 "
8 .000047 "
The duration increases with the striking distance, and is independent of
the diameter of the balls between which it is produced.
Spark Gap.
The space left between the ends of an electric resonator (see Resonator,
Electric) across which the spark springs. Its size may be adjustable by
a screw, something like the arrangement of screw calipers.
Sparking.
In dynamo-electric machines, the production of sparks at the commutator
between the brushes and commutator sections. The sparks are often true
voltaic arcs, and in all cases are injurious if in any quantity, wearing
out the commutator and brushes.
Sparking, Line or Points of Least.
In a dynamo or electric motor the diameter of the commutator
determining, or the points on the commutator marking the position of the
brushes where the sparking is a minimum. Field magnets powerful in
proportion to the armature are a preventative cause. The direction of
the line fixes the angle of lead to be given to the brushes.
Sparking, Resistance to.
The resistance to disruptive discharge through its substance offered by
a dielectric or insulator. It does not depend on its insulating
qualities, but on its rigidity and strength.
Spark, Length of.
The length of the spark accompanying the disruptive discharge is counted
as the distance from one electrode to the other in a straight line. It
is longer for an increased potential difference between the two
electrodes. If the gas or air between the electrodes is exhausted the
length increases, until the vacuum becomes too high, when the length
begins to decrease, and for a perfect vacuum no spark however small can
be produced. The shape of the conductor which is discharged, the
material of the electrodes, and the direction of the current are all
factors affecting the length of spark producible.
491 STANDARD ELECTRICAL DICTIONARY.
Spark Tube.
A tube used as a gauge or test to determine when the exhaustion of the
vacuum chamber or bulb of an incandescent lamp is sufficiently high.
The interior of the tube is connected with the interior of the bulb or
chamber of the lamps in process of exhaustion, and hence shares their
degree of exhaustion. From time to time connections with an induction
coil are made. When the exhaustion is carried far enough no discharge
will take place through the vacuum. As long as the tube acts like a
Geissler tube the exhaustion is not considered perfect.
Specific Heat of Electricity.
The heat absorbed or given out by a fluid in passing from one
temperature to another depends on its specific heat. In the Peltier and
the Thomson effects. q. v., the electric current acts as the producer of
a change of temperature, either an increase or decrease as the case may
be. This suggests an absorption of and giving out of heat which amount
of heat corresponding to a current of known amount is determinable, and
may be referred to any unit of quantity such as the coulomb. This or
some equivalent definite quantity of heat it has been proposed (Sir
William Thomson) to term the Specific Heat of Electricity.
Spent Acid.
Acid which has become exhausted. In a battery the acid becomes spent
from combination with zinc. It also loses its depolarizing power, if it
is a chromic acid solution or of that type, and then may be said to be
spent.
Spent Liquor.
The liquor of a plating bath which has become exhausted from use, the
metal it contained being all or partly deposited.
Sphygmograph, Electric.
An electric apparatus for recording the beat of the pulse, both as
regards its rate and strength.
Sphygmophone.
An apparatus for examination of the pulse by the microphone and
telephone.
Spiders.
Core-discs of a dynamo or motor armature are sometimes perforated with a
large central aperture, are fastened together with insulated bolts, and
the whole mass is secured to the shaft by three- or four-armed spiders.
These are like rimless wheels, the ends of their arms being secured to
the hollow cylinder constituting the armature core, and a central
aperture in their hub receiving the shaft.
492 STANDARD ELECTRICAL DICTIONARY.
Spiral.
This term is sometimes used instead of coil, as the primary spiral or
secondary spiral of an induction coil or transformer.
Spiral Winding.
The winding used on ring armatures. This may diagrammatically be
represented by a spiral carried around the ring shaped core. With two
field poles it gives two collecting points, positive and negative, with
four field poles it gives four collecting points, alternately positive
and negative.
Splice Box.
A box in which the splices in underground cables and electric lines are
contained. The splicing is generally done in the boxes with the cables
in place. They may be two-way for straight lines, or be four-way for two
side or lateral connections.
Spluttering.
A term applied to a sound sometimes produced in a voltaic arc, perhaps
caused by impure or insufficiently baked electrodes. (Elihu Thomson.)
Spring Control.
Control of or giving the restitutive force to the needle of a
galvanometer, core of a solenoid ammeter or moving part of any similar
instrument by a spring. As an example see Ammeter, Ayrton's.

Fig. 307. SPRING JACKS.
Spring Jack.
An arrangement for effecting, at one insertion of a species of plug, the
opening or breaking of a circuit and for the simultaneous connection to
the terminals formed by the breaking of two terminals of another system
or loop. Thus let a line include in its circuit two springs pressing
against each other, thereby completing the circuit. If a plug or wedge
of insulating material were inserted between the springs so as to press
them apart it would break the circuit and the whole would constitute a
spring jack cut-out. If each side of the plug had a strip of brass or
copper attached to it, and if the ends of another circuit were connected
to these strips, then the insertion of the plug would throw the new line
into the circuit of the other line.
493 STANDARD ELECTRICAL DICTIONARY.
Spring Jack Cut-out.
A cut-out, of the general construction of a spring jack, q. v., except
that a simple insulating plug or wedge is used in place of the
metal-faced wedge with its connections of the regular spring jack. The
insertion of an insulating wedge opens the circuit, which on its removal
is closed. The regular spring jack wedge will operate in the same way,
if its connections are kept open.
Spurious Voltage.
The voltage in excess of that developed by a secondary battery which is
required in the charging process. It is about .25 volt.
Square Wire.
Wire whose cross-section is a square. It has been used of iron for
building up the cores of armatures for dynamos or motors, for which it
is peculiarly suitable, and also of copper as a winding for armatures.
Staggering. adj.
When the brushes of a dynamo are set, one a little in advance of the
other on the surface of the commutator, they are said to be set
staggering. It is used to get over a break in the armature circuit.
State, Electrotonic.
A term expressing an abandoned theory. Faraday at one time proposed the
theory that a wire had to be in the electrotonic state to produce
electro-motive force by movement through an electric field. Any such
idea was ultimately abandoned by Faraday.
Static Breeze.
The electric breeze obtained by the silent discharge of high tension
electricity.
Static Electricity.
Electricity at rest or not in the current form ordinarily speaking. The
term is not very definite and at any rate only expresses a difference in
degree, not in kind. The recognition of the difference in degree has now
to a great extent also disappeared.
Station, Central.
The building or place in which are placed electrical apparatus, steam
engines and plant supplying a district with electric energy.
Station, Distant.
The place at the further end of a telegraph line, as referred to the
home station.
Station, Home.
The end of a telegraph line where the operators using the expression are
working.
494 STANDARD ELECTRICAL DICTIONARY.
Station, Transforming.
In alternating current distribution, a building or place where a number
of transformers are worked, so that low potential or secondary circuits
are distributed therefrom.
Steel.
A compound of iron with carbon. The carbon may range from a few
hundredths of one per cent. up to two per cent. For magnets, tool steel
drawn to a straw color or a little lower is good. All shaping and filing
should be done before magnetization.
Steeling.
The deposition of iron on copper plates by electrolysis. In
electrotyping a thin deposit of iron is thus given the relief plates
before printing from them. The deposit is very hard and exceedingly
thin, so that it does not interfere with the perfection of the
impression in the printing process. As the iron becomes worn it can be
dissolved off with hydrochloric acid, which does not dissolve the
copper, and a new deposit can be given it. Thus the plate may last for
an indefinite number of impressions.
The iron bath may be prepared by immersing in a solution of ammonium
chloride, two plates of iron, connected as anode and kathode in a
circuit. One plate dissolves while hydrogen is given off from the other.
The solution thus produced is used for a bath.
The hardness of the deposit, which is really pure iron, gives the name
of "steeling."
Synonym--Acierage.
St. Elmo's Fire.
Luminous static discharge effects sometimes seen on objects elevated in
the air. They are especially noticed on ships' masts. The sailors term
them corpusants (holy bodies). They resemble tongues or globes of fire.
Step-by-step Telegraphy.
A system of telegraphy in which in the receiving instrument a hand is
made to move step-by-step, with an escape movement around a dial. For
each step there is a letter and the hand is made to stop at one or the
other letter until the message is spelled out. (See Dial Telegraph.)
Step-down. adj.
A qualification applied to a converter or transformer in the alternating
current distribution, indicating that it lowers potential difference and
increases current from the secondary.
Step-up. adj.
The reverse of step-down; a qualification of a transformer or converter
indicating that it raises the potential and decreases the current in the
secondary.
Sticking.
The adherence, after the current is cut off, of the armature to the
poles of a magnet. In telegraphy it is a cause of annoyance and
obstructs the working. It may, in telegraphy, be due to too weak a
spring for drawing back the armature, or to imperfect breaking of the
contact by the despatcher's key or by the receiver's relay.
495 STANDARD ELECTRICAL DICTIONARY.
Stopping Off.
In electroplating the prevention of deposition of the plating metal on
any desired portions of the object. It is effected by varnishing the
places where no coating is desired. An article can be plated with
silver, stopped off in any desired design, and the unvarnished portions
may then be plated with gold in another bath. Various effects can be
produced by such means.
Storage Capacity.
A term for the ampere-hours of electricity, which can be taken in
current form from a storage battery.
Storage of Electricity.
Properly speaking electricity can only be stored statically or in static
condensers, such as Leyden jars. The term has been popularly applied to
the charging of secondary or storage batteries, in which there is really
no such thing as a storage of electricity, but only a decomposition and
opposite combination brought about, which leave the battery in a
condition to give a current.
Storms, Electric.
Wide-spread magnetic and electric disturbances, involving the
disturbance of the magnetic elements and other similar phenomena. (See
Magnetic Storms.)
Strain.
The condition of a body when subjected to a stress. Various consequences
may ensue from strain in the way of disturbance of electric and other
qualities of the body strained.
Stratification Tube.
A Geissler tube, q. v., for showing the stratification of the electric
discharge through a high vacuum.
The stratifications are greatly intensified by the presence of a little
vapor of turpentine, alcohol, bisulphide of carbon and other substances.
Stray Field.
In a dynamo or motor the portion of the field whose lines of force are
not cut by the armature windings.
Stray Power.
The proportion of the energy wasted in driving a dynamo, lost through
friction and other hurtful resistances.
Streamlets, Current.
A conception bearing the same relation to an electric current that lines
of force do to a field of force; elementary currents. If evenly
distributed the current is of uniform density; if unevenly distributed,
as in alternating currents, the current density varies in different
parts of the cross section of the conductor. This evenness or unevenness
may be referred to the number of streamlets per unit of area of
cross-section.
[Transcriber's note: Streamlets per unit of area is redundant with
current density.]
Stress.
Force exercised upon a solid tending to distort it, or to produce a
strain.
496 STANDARD ELECTRICAL DICTIONARY.
Stress, Dielectric.
The condition of a dielectric when maintaining a charge; its two
extremities are in opposite states of polarity, or are under permanent
potential difference. As the two opposite polarities tend to unite a
condition of stress is implied in the medium which separates them.
Stress, Electro-magnetic.
The stress produced upon transparent substances in an electro-magnetic
field of force. It is shown in the modified optical properties of glass
and similar substances placed between the poles of a strong
electro-magnet.
Stress, Electrostatic.
The stress produced upon substances in an electrostatic field of force;
the exact analogue of electro-magnetic stress, and affecting transparent
substances in the same general way.
Striae, Electric.
In Geissler tubes the light produced by the electric discharge is filled
with striae, bright bands alternating with dark spaces; these may be
termed electric striae.
Striking Distance.
The distance that separates two conductors charged with electricity of
different potential, when a spark starts between them.
Striking Solution.
In silver-plating a bath composed of a weak solution of silver
cyanide-with a large proportion of free potassium cyanide. It is used
with a strong current and a large silver anode. This gives an
instantaneous deposition of metallic silver over the surface of the
article which goes to insure a perfect coating in the silver bath
proper. After a few seconds in the striking solution, the article is at
once removed to the plating bath.
Stripping.
The removal of electroplating from an object. It may be effected in
several ways. An object whose plating is to be removed is placed in a
plating bath of the solution of the metal with which it is coated. It is
connected as the anode to the positive plate of the battery or
corresponding terminal of the generator. A kathode connected to the
other terminal being placed in the bath, the coating is dissolved by
electrolytic action. Sometimes simple treatment with acid is employed.
Different stripping baths are described under the heads of the different
metals.
S. U.
Symbol or abbreviation for Siemens' Unit of Resistance. (See Resistance,
Siemens' Unit of.)
Sub-branch.
A branch or lead of wire taken from a branch lead: a term used in
electric distribution.
Sub-main.
In electric distribution a conductor connected directly to a main; a
branch.
497 STANDARD ELECTRICAL DICTIONARY.
Subway, Electric.
A subterranean system of conduits for electric cables. As generally
constructed in this country it includes manholes, q. v., at the street
corners connected by ducts or pipes. These pipes are large enough to
hold a cable. To introduce a cable into a duct, which latter may be two
or three inches in diameter, and from two hundred to six or seven
hundred feet long, a wire or rope is first passed through the duct. This
is done by a set of short wooden rods with screws at the end so as to be
screwed together. Each rod must be shorter than the diameter of the
manhole. A rod is thrust in, another is screwed to it and thrust in, and
thus a set of rods is made to extend as far as desired. In pulling them
out a rope is attached and drawn through. This rope or a larger one is
used in drawing the cable through the duct. A windlass is employed to
draw the rope with cable attached through the ducts.
Sulphating.
In storage battery cells, the formation of a hard white basic lead
sulphate, Pb2 S05. Its formation is due to over-exhaustion of the cells.
As long as the voltage is not allowed to fall below 1.90 volts per cell
little of it forms. As it accumulates it is apt to drop off the plate
and fall to the bottom, thus weakening the plate possibly, and depriving
it of active material, and clogging up the cell. If it carries a film of
metallic lead with it, there is danger of short circuiting the cell.
The presence of some sodium sulphate in the solution is said to tend to
prevent sulphating, or to diminish it.
Sulphur Dioxide.
A compound gas, S O2; composed of
Sulphur, 32
Oxygen, 32
Molecular weight, 64
Specific gravity, 2.21.
It is a dielectric of about the same resistance as air. Its specific
inductive capacity at atmospheric pressure is: 1.0037 (Ayrton).
Synonyms--Sulphurous Acid--Sulphurous Acid Gas.
Sunstroke, Electric.
Exposure to the arc light sometimes produces the effects observed in
cases of sunstroke. It is said that, in the case of workmen at electric
furnaces, these effects are very noticeable. (See Prostration,
Electric.)
[Transcriber's note: Effects are due to ultraviolet light.]
Supersaturated. adj.
A liquid is supersaturated when it has dissolved a substance at a
temperature favorable to its solubility and its temperature has been
allowed to change, the liquid being kept free from agitation or access
of air, provided crystallization or precipitation has not taken place.
It expresses the state of a liquid when it holds in solution more than
the normal quantity of any substance soluble in it.
Surface.
A galvanic battery is arranged in surface when all the positive plates
are connected together and all the negative plates are also connected.
This makes it equivalent to one large cell, the surface of whose plates
would be equal to the aggregate surface of the plates of the battery. It
is also used as an adjective, as "a surface arrangement of battery."
498 STANDARD ELECTRICAL DICTIONARY.
Surface Density.
The relative quantity of an electric charge upon a surface.
Surface, Equipotential.
A surface over all of which the potential is the same. In a general
sense equipotential surfaces are given by planes or surfaces which cut
lines of force at right angles thereto, or which are normal to lines of
force. The conception applies to electrostatic and electro-magnetic
fields of force, and for current conductors the planes normal to the
direction of the current are equipotential surfaces.
The contour of an equipotential surface of a field of force which is
drawn or represented by delineations of its lines of force can be
obtained by drawing a line normal thereto. This line will ordinarily be
more or less curved, and will be a locus of identical potentials.
An electric equipotential surface may be described as electro-static,
electro- magnetic, or magnetic; or may be an equipotential surface of a
current conductor. Besides these there are mechanical and physical
equipotential surfaces, such as those of gravitation.
Surface Leakage.
Leakage of current from one part of an insulating material to another by
the film of moisture or dirt on the surface.
Suspension.
This term is applied to methods of supporting galvanometer needles,
balance beams, magnetic compass needles and similar objects which must
be free to rotate. (See Suspension, Bifilar--Fibre and Spring
Suspension--Fibre Suspension--Knife Edge Suspension--Pivot
Suspension--Suspension, Torsion.)