The Standard Electrical Dictionary Part 145

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 pa.s.s through the gla.s.s. 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 ill.u.s.trate 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 a.n.a.logous 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.

s.p.a.ce, Clearance.

The s.p.a.ce 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 s.p.a.ce is a mechanical factor; the air gap is an electric or magnetic factor.

Synonym--Inter-air s.p.a.ce.

s.p.a.ce, Crookes' Dark.

In an exhausted tube, through which an electric discharge is caused to pa.s.s, the s.p.a.ce surrounding the negative electrode of the tube. This s.p.a.ce 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 s.p.a.ce fills the whole s.p.a.ce 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.

s.p.a.ce, Faraday's Dark.

The s.p.a.ce in an exhausted tube between the luminous glows about the two electrodes.

s.p.a.ce, 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 s.p.a.ce, 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 b.a.l.l.s between which it is produced.

Spark Gap.

The s.p.a.ce 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.