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Safety Fuse. A device to prevent overheating of any portion of a circuit by excessive current. It generally consists of a strip of fusible metal which, if the current attains too great strength, melts and opens the circuit.
Salt. A chemical compound containing two atoms or radicals which saturate each other. One is electro-positive, the other electro-negative.
Salts are decomposed by electrolysis, and in separating they combine to form new molecules.
Saturated. A liquid is said to be saturated when it has dissolved all the salts it will take up.
Search-light. An apparatus for producing a powerful beam of light and projecting it in any desired direction.
Secondary. A term applied to the secondary coil of a transformer or induction-coil.
Secondary Battery. (See [Battery, Secondary].)
Secondary Plates. The plates of a secondary battery or storage-battery. When charged, the negative plate should be brown or deep reddish in color, and the positive slate-colored.
Self-excited. Electrified by its own current.
Self-winding Clock. A clock which automatically winds itself by electricity. It is operated by a small electro-magnetic motor which obtains its current from an outside source.
Semaphore, Electric. An apparatus for exhibiting signals. Used in the railway block system.
Series. Arranged in succession. When incandescent lamps are installed so that the current goes in and out of one lamp, and so on to the next and the succeeding ones, they are said to be arranged in series. It takes high E-M-F and current, or amperage, to operate such lamps.
Series batteries are arranged with the zinc pole of one connected to the carbon pole of the next.
Series Arc Cut-out. A device by means of which a short circuit is established past a defective lamp, thereby securing the undisturbed operation of all the other lamps in the circuit.
Series Distribution. A distribution of electricity in which the receptive devices are arranged in successive order upon one conductor, extending the entire length of the circuit.
Series Dynamo. A series-wound dynamo.
Series Incandescent Lamp. An incandescent lamp adapted for service in a series circuit.
Series Motor. A motor adapted for use in a series circuit; a motor whose field-coil winding is in series with the armature.
Series, Multiple. An arrangement of electric apparatus in which the parts are grouped in sets in parallel, and these sets are connected in series.
Series Winding. A method of winding a generator or motor in which one of the commutator brush connections is joined to the field-magnet winding. The other end of the magnet winding is connected with the outer circuit, and the second armature brush is coupled with the remaining terminal of the outer circuit.
Service Wires. Wires connected to the supply circuit or main wires, and which run into buildings to supply current for heat, light, and power.
Shellac. A resin gum, gathered from certain Asiatic trees. It is soluble in alcohol, and is used extensively in electric work as an insulator.
Shifting Magnetic Field. (See [Magnetic Field, Shifting].)
Shock, Electric. The effect upon the animal system of the discharge of an electric current of high potential difference. The voltage is the main element in a shock.
Shoe. As applied to electric railways, the casting employed to bear on the third rail to take in positive current and electro-motive force.
The cast-iron plate of an electric break, which, by magnetism, adheres to another iron surface.
Short Circuit. (See [Circuit, Short].)
Shunt-box. A resistance-box designed for use as a galvanometer shunt. The box contains a series of resistance-coils which can be plugged in or out as required.
Shunt-winding. A dynamo or motor is shunt-wound when the field-magnet winding is parallel with the winding of the armature.
Silver-bath. A solution of a salt of silver used in the electro-plating process.
Silver-plating. Depositing a coating of silver on a metallic surface by the acid of electro-metallurgy.
Silver-stripping Bath. An acid solution used for stripping silver from a metallic surface before re-plating it.
Simple Circuit. (See [Circuit, Simple].)
Simple Immersion. (See [Immersion, Simple].)
Simple Magnet. (See [Magnet, Simple].)
Single-trolley System. A trolley system employing only one overhead conducting wire, the track and ground serving as the return-circuit.
Single-wound Wire. Wire insulated by winding or overlaying with but a single layer of material.
Sliding-condenser. (See [Condenser, Sliding].)
Snap-switch. A switch so contrived as to give a quick break. A spiral spring is fastened between the handle and arm in such a manner that when the handle is drawn back the spring operates and quickly draws a knife-bar from the keeper, breaking the contact instantly and without the formation of an arc.
Socket. A receptacle for an incandescent lamp or plug.
Solenoid. A helical coil of wire of uniform diameter or cylindrical in shape. It is useful in experiments with electro-magnetism.
Solution. A fluid composed of dissolved salts; a mixture of liquids and fluids.
Sound Waves. Waves produced in an elastic medium by sonorous vibration, as in wireless telegraphy.
Sounder. In telegraphy, the instrument operated on by the key at the other end of a line. Various devices are employed to increase their resonance—as, for instance, hollow boxes. Sounders are generally placed on local circuits and are actuated by relays.
Sounder, Repeating. A telegraphic instrument which repeats a message into another circuit.
S-P. An abbreviation for single pole.
Spark-arrester. A screen of wire-netting fitted around the carbons of arc-lamps to prevent the chips or hot sparks from flying.
Spark-coil. A coil for producing a spark from a source of comparatively low electro-motive force. The induction-coil is an example.
Spark, Electric. The phenomenon observed when a disruptive charge leaves an accumulator or induction-coil and passes through an air gap.
Spark-gap. The space left between the ends of an electric resonator across which the spark springs.
Sparking. The production of sparks at the commutator, between the bars and the brushes of dynamos and motors. They are minute voltaic arcs, and should not be allowed to occur, as they cut away the metal and score the surface of the commutator.
Spark-tube. A tube used as a gauge to determine when the exhaustion of the vacuum chamber, or bulb, of an incandescent lamp is sufficiently high.
Specific Gravity. The relative weight or density of a body as compared with a standard. Water is usually taken as a standard for solids and liquids, and air for gases.
Speed-counter. An instrument which records the number of revolutions a shaft makes in a given time.
Spent Acid. Acid which has become exhausted. In a battery the acid becomes spent from combination with zinc; it also loses its depolarizing power.
Spring-contact. A spring connected to one lead of an electric circuit. It is arranged to press against another spring or contact, which it opens or closes by the introduction of a plug or wedge.
Spring-jack. An arrangement of spring-arm conductors under which plugs with wires attached can be slipped to make a new connection or to cut out certain circuits.
Spurious Resistance. (See [Resistance, Spurious].)
Standard Candle. (See [Candle, Standard].)
Standard Resistance. (See [Resistance, Standard].)
Starting-box. A resistance or shunt box used for letting current pass gradually into motors, instead of throwing on the full current at once.
Static Electricity. Electricity generated by friction; frictional electricity, such as lightning; electricity of high electro-motive force and practically uncontrollable for commercial purposes.
Static Shock. A term used in electro-therapeutics for describing the discharge from a small condenser or Leyden-jar; also the effect produced by the action of the vibrator of the induction-coil.
Station, Central. The building or place in which the electrical apparatus is installed for the generation of current; the headquarters of telephone lines.
Steady Current. An electric current whose strength is fixed or invariable.
Stock-ticker. An instrument employed to give quotations of stocks by telegraphic record. A paper tape runs through an electrical machine which prints on it the figures and letters that stand for stocks and their values. The whole system is operated from a station located in the Stock-exchange.
Storage Accumulator. (See [Accumulator, Storage].)
Storage-battery. (See [Battery, Storage].)
Strength of Current. Amperage; the quantity of current in a circuit.
Stripping. The process of removing electro-plating, or thin metal coatings, from an object before it is re-electro-plated.
Stripping Liquid. The liquid in a stripping-bath used for removing metals from surfaces before re-plating them.
Submarine Cable. A telegraphic cable laid at the bottom of the sea or any body of water.
Submarine Search-light. An incandescent light which works under water.
Sub-station. A generating or converting plant subsidiary to a central station, and placed so as to supply current in a district situated at a distance from the main power-house.
Subway, Electric. An underground passageway utilized for carrying cables and wires.
Sweating. A process by which the ends of cables are brought together and soldered.
S-W-G. An abbreviation for standard wire gauge.
Switch. A device for opening and closing an electric circuit. Made in a great variety of forms, such as push-button, telegraph-key, knife switch, automatic switch, lever switch, rheostat, etc.
Switch-bell. A combined bell and switch. The bell is operated when the switch is opened or closed.
Switch-blade. The blade of a switch; a conducting strip connecting two contact-jaws.
Switch-board. A board or table to which wires are led and connected with cross-bars or other devices by which connections can be made.
Synchronize. To agree in point of time; to effect concurrence of phase in two alternating-current machines, in order to combine them electrically.