M
Magnet. A substance or metal having the power to attract iron and steel.
Magnet-bar. A magnet in the shape of a straight bar. (See Bar-magnet.)
Magnet-coil. A coil of insulated wire enclosing a core of soft iron through which a current of electricity is passed to magnetize the iron.
Magnet-core. An iron bar or mass of iron around which insulated wire is wound in order to create an electro-magnet.
Magnet, Electric. A magnet consisting of a bar of iron, a bundle of iron wires, or an iron tube, around which a coil of insulated wire is wound. When a current is passing through the coil its influence magnetizes the iron core, but directly the current ceases the magnetism disappears.
Magnet, Field. The electro or permanent magnet in a dynamo or motor, used to produce the area of electric energy.
Magnet, Horseshoe. A magnet of U shape with the poles or ends brought closer together than the other parts of the limbs. A soft iron bar is placed across the poles when not in use, as this serves to conserve the magnetism.
Magnet, Permanent. A term applied to a hard steel magnet possessing high retentivity, or the power to hold its magnetism indefinitely.
Magnet, Regulator. An electro-magnet whose armature moves in such a manner as to automatically shift the commutator-brushes, on a motor or dynamo, to a position which insures the preservation of both brushes and commutator-bars, and also produces a constant current.
Magnet, Simple. A magnet made of one piece of metal.
Magnet Wire. Insulated wire used for coils. Cotton or silk covered wire is the most serviceable for winding magnets.
Magnetic Adherence. The tendency of a mass of iron to adhere to the poles of a magnet.
Magnetic Attraction and Repulsion. The attraction of a magnet for iron, steel, nickel, and cobalt; also of unlike poles of magnets for each other. The like poles repel.
Magnetic Circuit-breakers. An automatic switch, or breaker, whose action is excited and controlled by an electro-magnet.
Magnetic Concentration of Ores. The separation of iron and steel from their gangue by magnetic attraction. It is applicable only when either the ore or the gangue is susceptible to the magnet.
Magnetic Control. The control of a magnetic needle, magnet, index, armature, or other iron indicator in a galvanometer, ammeter, or voltmeter by a magnetic field.
Magnetic Dip. The inclination from the horizontal position of a magnetic needle that is free to move in a vertical plane.
Magnetic Field, Rotary. A magnetic field resulting from a rotary current.
Magnetic Field, Shifting. A magnetic field which rotates. Its lines of magnetic force vary, therefore, in position.
Magnetic Field, Uniform. A field of uniform strength in all portions, such as the magnetic field of the earth.
Magnetic Force. The power of attraction and repulsion exercised by a magnet; the force of attraction and repulsion which a magnet exercises, and which, in its ultimate essence, is unknown to science.
Magnetic Induction. (See Induction, Magnetic.)
Magnetic Needle. A magnet having a cup or small depression at its centre, and poised on a sharp pin of brass, so as to be free to rotate. Its N pole points to the north, and its S pole to the south. A compass needle.
Magnetic Poles. The terrestrial points towards which the north or south poles of the magnetic needle are attracted. There are two poles: the arctic, or negative, which attracts the positive or N pole of the magnetic needle; and the antarctic, or positive, which attracts the S pole of the needle.
Magnetic Poles, False. It has been established that there are other poles on the earth that attract the magnetic needle when the latter is brought into their vicinity. These are called false poles, and are probably caused by large deposits of iron lying close to the surface of the earth.
Magnetic Separator. An apparatus for separating magnetic substances from mixtures. It is used chiefly in separating iron ore from earth and rock. The mineral falls on an iron cylinder, or drum, magnetized by coils, and adheres there, while the earth or crushed rock drops below. The particles of iron are afterwards removed by a scraper. The machine is also used in separating iron filings and chips from brass, copper, or other metals, the iron adhering to the magnet, while the brass and other chips drop underneath.
Magnetism. The phenomena of attraction exerted by one body for another. It has been commonly understood that magnetism and electricity are very closely related, for without electricity magnetism could not exist, although it has not been shown clearly that magnetism plays any part in the generation of electricity. Magnetism is the phenomenal force exerted by one body having two poles (negative and positive) for like bodies. The horseshoe magnet or a bar of magnetized steel are the simplest examples of this. If both ends of the horseshoe were positive they would not attract, but would repel. If both ends of a bar were positive they would repel; but as one is negative, or north-seeking, and the other positive, they exert lines of force which attract like bodies, such as bits of iron, nails, and needles. No energy is required to maintain magnetism in a tempered steel object, such as the wiring about a soft iron core when it has been magnetized, but electric current must flow about the soft iron core in order to render it a magnet. So soon as the current ceases to flow the magnetism ceases and the soft iron fails to attract.
Magnetism, Uniform. Magnetism that is uniform throughout a mass of magnetic steel, or a core that is electro-magnetic.
Magnetize. To impart magnetic property to a substance capable of receiving it.
Magnetizing-coil. (See Coil, Magnetizing.)
Magneto Call-bell. A call-bell used principally in telephone systems, and operated by a current from a magneto-electric generator. The current is excited by turning the handle at the side of the telephone-box before removing the receiver from the hook.
Magneto-generator. A current-generator composed of a permanent magnet and a revolving armature which is rotated between the poles of the permanent magnet.
Main Circuit. (See Circuit, Main.)
Main Feeder. The main wire in a district to which all the feeder wires are attached.
Main Switch. The switch connected to the main wire of a line, or the main-switch controlling a number of auxiliary switches.
Mains, Electric. The large conductors in a system of electric light or power distribution.
Make and Break, Automatic. An apparatus which enables the armature of a magnet to make and break its circuit automatically.
Make-and-break Current. (See Current, Make-and-break.)
Mercurial Air-pump. An air-pump operated by mercury to obtain a high vacuum, and used extensively for exhausting incandescent-lamp bulbs.
Mercury Tube. A glass tube sealed and containing mercury. It is so arranged as to give out fluorescent light when shaken or agitated by an electric current. For example, the Geissler tubes, the Cooper-Hewitt light, Crook’s tubes, etc.
Metallic Arc. An arc which forms between metallic electrodes.
Metallic Circuit. (See Circuit, Metallic.)
Metallic Conductor. A conductor composed of a metal.
Metallic Filament. A metal wire used in an incandescent lamp—the filament.
Metallic Resistance. (See Resistance, Metallic.)
Metallurgy. The art of working metals. Electro-metallurgy applies to the processes wherein electricity plays the most important part.
Mica. A natural mineral of sheet form and translucent, used extensively as an insulator in electrical equipment and mechanism.
Mica, Moulded. A composition composed of ground mica and shellac as a binder. When heated and pressed into various shapes and forms, it is a valuable insulator, and is employed for hooks, locks, tubes, sockets, and the like.
Micanite. An insulating material made by cementing laminations of pure mica together and cementing them with shellac or other suitable non-conducting adhesives.
Molecular Adhesion. The attraction of similar molecules for each other.
Molecular Attraction. The attraction of molecules, or physical affinity.
Molecular Resistance. The resistance which a mass or electrolyte offers when contained in an insulated vessel and a current of electricity is passed through it.
Molecule. One of the invisible particles supposed to constitute matter of every kind; the smallest particle of matter that can exist independently. It is made up of atoms, but an atom cannot exist alone.
Morse Receiver. The receiving instrument once universally used in the Morse system of telegraphy, but now superseded by the sounder.
Morse Recorder. An apparatus which automatically records on a ribbon of paper the dots and dashes of the Morse telegraph alphabet.
Morse Sounder. An electro-magnetic instrument designed to make a sharp, clicking sound when its armature lever is drawn down by the attraction of the magnets.
Morse System. A telegraphic system invented by Prof. S. F. B. Morse, in which, by means of alternating makes and breaks of varying duration, the dots and dashes of the Morse alphabet are reproduced and received at a distance through the agency of wires and the electro-magnetic sounder.
Motor, Electric. A machine or apparatus for converting electric energy into mechanical kinetic energy or power. The electrical energy is usually generated by a dynamo, and distributed on conductors to motors located at various points.
Electric motors are of two types—the A-C., or alternating current, and the D-C., or direct current.
Motor-car, Electric. A self-propelling car driven by stored electricity.
Motor-dynamo. A motor driven by a dynamo whose armature is firmly attached or connected to that of the dynamo. It is used for modifying a current. If the dynamo generates an alternating current of high potential, the motor converts it into a direct current of lower voltage but increased amperage.
Motor-transformer. A transformer which is operated by a motor.
A dynamo-electric machine provided with two armature windings, one serving to receive current, as a motor, the other to deliver current, as a generator, to a secondary circuit.
N
N. An abbreviation for the north-seeking pole in a magnet.
Natural Magnet. A loadstone.
Needle. A term applied to a bar-magnet poised horizontally upon a vertical point.
A magnetic needle, or the magnet in a mariner’s compass.
Negative. Opposed to positive.
Negative Electricity. The kind of electricity with which a piece of amber is charged by friction with flannel.
In a galvanic battery or cell the surface of the zinc is charged with negative electricity. Negative electricity, according to the theory of some scientists, really means a deficiency of electricity.
Negative Electrode. The same as Negative Element.
Negative Element. The plate not dissolved by the solution in a voltaic cell; the one which is positively charged.
The carbon, platinum, or copper plate or pole in a battery.
Negative Feeder. The conductor which connects the negative mains with the negative poles of a generator.
Negative Plate. (See Plate, Negative.)
Negative Pole. (See Pole, Negative.)
Neutral Feeder. The same as Neutral Wire.
Neutral Wire. The central wire in a three-wire system.
Nickel-bath. A bath for the electro-deposition of nickel.
Non-arcing Fuse. A fuse-wire which is enclosed in a tube packed with asbestos or silk, and which does not produce an arc when it fuses or blows out. It is practically noiseless, save for a slight hissing sound, accompanied by a light puff of smoke, which escapes from a venthole in the side of the tube.
Non-conductor. A material or substance offering very high resistance to the passage of the electric current.
Non-magnetic Steel. Alloys of iron incapable of being magnetized. They are composed of iron and manganese, nickel, steel, etc.
Normal. Regular. The average value of observed quantities. Normal current is a regular current without variations.
The force of a current at which a system is intended to work.
Normal Voltage. The same as Normal Current.
North Pole. The north-seeking pole of a magnet.
The pole of a magnet which tends to point to the north, and whence lines of force are assumed to issue on their course to the other pole of the magnet.
O
O. An abbreviation for Ohm.
Oersted’s Discovery. Oersted discovered, in 1820, that a magnetic needle tended to place itself at right angles to a current of electricity. This fundamental principle is the basis of the galvanometer, the dynamo, and the motor.
Ohm. The practical unit of resistance. A legal ohm is the resistance of a column of mercury one square millimetre in cross-sectional area and 106.24 centimetres in length.
Ohm, True. The true ohm is the resistance of a column of mercury 106.24 centimetres long and one square millimetre in cross-sectional area. An ohm may be measured by a No. 30 copper wire nine feet and nine inches long. If larger size wire is used the piece must be proportionately longer, since the resistance is less.
Ohmic Resistance. True resistance as distinguished from spurious resistance, or counter electro-motive force. (See also Resistance, Ohmic.)
Ohm’s Law. The basic law which expresses the relations between current, electro-motive force, and resistance in active circuits. It is formulated as follows:
1. The current strength is equal to the electro-motive force divided by the resistance.
2. The electro-motive force is equal to the current strength multiplied by the resistance.
3. The resistance is equal to the electro-motive force divided by the current strength.
O. K. A telegraphic signal meaning yes, or all right. It is supposed to be a misspelled form of all correct, “Oll Kerrekt.”
Okonite. A form of insulation for wires and conductors; a trade name applied to insulations, and protected by copyright.
Open Arc. A voltaic arc not enclosed.
Open Circuit. (See Circuit, Open.)
Oscillating Current. (See Current, Oscillating.)
Outlet. That part of an electrolier or electric light fixture out of which the wires are led for attachment to incandescent light sockets.
Outside Wiring. The wiring for an electric circuit which is located outside a building or other structure.
Overhead Feeders. The same as overhead conductors.
Overhead Trolley. The system in which the current for the propulsion of trolley-cars is taken from overhead feeders or wires.
Overhead Trolley-wire. A naked, hard copper wire drawn at high tension, and suspended over or at the side of a car-track, and from which the trolley-wheel takes its current.
Overload. In an electric motor, an excess of mechanical load prevents economical working, causing the armature to revolve slowly and the wiring to heat. In this case heating implies waste of energy.
Overload Switch. A switch which operates automatically to open a circuit in line with a motor, and so save the motor from overheating or burning in the event of an overload.
P
Paper Cable. A cable insulated with waxed or paraffined paper.
Paraffine. A residuum of petroleum oil, valuable as an insulating medium in electrical work.
A hydro-carbon composition of the highest resistance known. It is extensively used in condensers and other electrical apparatus as a dielectric and insulator.
Parallel Distribution. A distributing system for electricity wherein the receptive contrivances are adjusted between every two of a number of parallel conductors running to the limits of the system. When two or more conductors connect two mains of comparatively large size and low resistance, they are said to be in parallel or in multiple. This order is easily pictured by imagining the mains to be the sides of a ladder and the conductors the rungs. In the latter the lamps are placed. It follows that the current flows from one main to the other through the conductors and lamps.
Paramagnetic. Substances which have magnetic properties, or those which are attracted by magnetic bodies. A paramagnetic substance has high multiplying power for lines of force, therefore a bar of iron which is a paramagnetic substance of the highest quality becomes magnetic when placed within a circle of electric lines of force. The first example of paramagnetic substance brought to the attention of man was the lodestone, from which the ancient mariners fashioned their crude compass needles.
P-C. An abbreviation for porous cup.
Pear Push. A push-button enclosed in a handle having the shape of a pear. It is generally attached to the end of a flexible wire cord.
Periodic Current. (See Current, Periodic.)
Permanency, Electric. The power of conductors to retain their conductivity unaffected by the lapse of time.
Permanent Magnet. (See Magnet, Permanent.)
Phase. One complete oscillation. The interval elapsing from the time a particle moves through the middle point of its course to the instant when the phase is to be stated.
Simple harmonic motion. Oscillation.
’Phone. An abbreviation for the word Telephone.
Phonograph. An apparatus for reproducing sound. It is vibratory and not electric in its action, except that the mechanism may be driven by electricity. It consists of a rotating cylinder of a waxlike material and a glass diaphragm carrying a needle-point that lightly touches the surface of the waxen cylinder. If the diaphragm is agitated the needle vibrates, making indentations in the surface of the wax. If the needle is set back and the cylinder rotated so as to carry the point over the indentations, the sound is given back through the vibration of the diaphragm.
Pickle. An acid solution used to cleanse metallic surfaces preparatory to electro-plating.
Pilot Wires. Wires brought from distant parts of electric light and power mains, and leading to voltmeters at a central station. Through their agency the potential energy of every part of the system may be measured.
Pith-balls. Balls made from the pith of light wood, such as elder. They are used in the construction of electroscopes and for other experiments in static electricity.
Plant. The apparatus for generating electric current, including engines, boilers, dynamos, mains, and subsidiary apparatus.
Plate, Condenser. In a static apparatus, the condenser having a flat piece of glass for a dielectric. It is mounted on an axle so that it may be revolved.
Plate, Ground. In a lightning-arrester, the plate connected to the earth or ground wire.
Plate, Negative. In a voltaic battery, the plate which is unattacked by the fluid. It is made of carbon, platinum, or copper.
Plate, Positive. (See Positive Plate.)
Plating-bath. A vessel of solution for the deposition of metal by electrolysis. Used in electro-plating.
Plating, Electro. The process of depositing metal on surfaces of metals or other substances by the aid of an electrolyte and the electric current.
Platinum Fuse. A slender wire of platinum roused to incandescence by current, and used to explode a charge of powder or other combustible substance.
Plug. A piece of metal, with a handle, used to make electric connections by being inserted between two slightly separated plates or blocks of metal.
A wedge of metal, slightly tapered, and used to thrust between two conductors to close or complete a circuit.
Plumbago. Soft, lustrous graphite; a native form of carbon sometimes chemically purified. It is used chiefly in electrotyping for dusting the wax moulds to make the surface an electric conductor.
Plunge-battery. (See Battery, Plunge.)
Polar. Pertaining to one of the poles of a magnet.
Polarity. The disposition in a body to place its axis in a particular direction when influenced by magnetism. For example, the attraction and repulsion at the opposite ends of a magnet. The N and S seeking poles of a compass needle is the simplest example.
Polarity, Electric. The disposition in a paramagnetic body to be influenced by electric waves and lines of force. The otherwise non-magnetic body or mass becomes magnetic to attract or repulse when influenced by electricity, but ceases to retain the phenomena after the electric influence is removed. A piece of soft iron wire, a nail, or a short rod of iron will become electro-polarized when a current of electricity is sent through a coil of insulated wire so wound that one end will be N the other S. So soon as the circuit is broken the polarity ceases.
Polarization. The depriving of a voltaic cell of its proper electro-motive force. This may be brought about through the solution becoming spent, or in the event of the acid being saturated with zinc, and so failing to act on the metallic zinc.
Counter electro-motive force due to the accumulation of hydrogen on the negative plate.
Polarizing-current. (See Current, Polarizing.)
Polar Surface. The surface of a magnetic substance through which the magnetic flux passes in or out.
Pole-changer. An automatic, oscillating switch or contact-breaker which reverses the direction of the current.
Pole, Negative. The S pole in a magnet or compass needle.
Pole, Positive. (See Positive Pole.)
Pole-switch, Single. A switch designed to open or close one lead only.
Poles. The terminals of an open electric circuit at which there necessarily exists a potential difference.
The terminals of an open magnetic circuit, or the ends of a magnetized mass of iron.
Porcelain. A fine variety of earthenware, valuable for insulators and insulating purposes.
Porosity. The state or property of having small interstices or holes. The opposite of density.
Porous Cup or Cell. A cup or cell made of pipe-clay or of unglazed earthenware through which a current of electricity can pass when wet or in a liquid. Porous cups are used in cells and batteries to keep two liquids apart, and yet permit electrolysis and electrolytic conduction.
Positive Currents. Currents which deflect the needle to the left.
Positive Electricity. The current that flows from the active element, the zinc in a battery, to the carbon. The negative electricity flows from the carbon to the zinc.
Positive Electrode. The electrode which is connected with the positive pole of a source of electric energy.
Positive Feeders. The lead or wire in a set of feeders which is connected to the positive terminal of the generator.
Positive Plate. In a voltaic cell, the plate which is acted upon and corroded. The current from the positive plate is negative electricity.
Positive Pole. The N pole in a magnet or magnetic needle. So called because it seeks the north or negative pole of the earth.
Positive Wire, or Conductor. The wire, or conductor, connected with the positive pole of any apparatus which produces electro-motive force.
Potential, Electric. The power to perform electric work.
Potential Energy. Capacity for doing work. Potential energy when liberated becomes actual energy for the performance of work.
Power-generator. Any source from which power is generated.
Power-house. A station in which the plant of an electric power system is operated and the current distributed to local or long-distance points. Power-houses are either primary or secondary stations. In the primary station the current is generated directly by the aid of mechanical power, either the steam-engine or the steam-turbine. The secondary station, or sub-station, is located at a distance from the main power-house, and has no mechanical means of generating current. The current, usually of high alternating voltage, is supplied to the sub-station from the main power-house; and by means of transformers and converters, the high-voltage current is transformed into one of lower E-M-F and higher amperage, for distribution over local lines.
Power-unit. The unit of electric power is the volt-ampere or watt.
Pressure, Electric. Electro-motive force or voltage.
Primary. A term used to designate the induction-coil in an induction-apparatus or transformer. It is an abbreviation for primary coil.
Primary Battery. (See Battery, Primary.)
Prime Conductor. (See Conductor, Prime.)
Push-button. A switch for closing a circuit by means of pressure applied to a button. The button is provided with a spring, so that when pushed in and released it flies back, reopening the circuit.
Pyrogravure. A process of engraving by the use of platinum points heated to redness by the electric current.
Q
Q. Abbreviation or symbol for electric quantity.
Quadrant. The quarter of a circle or of its circumference.
Quadruple Circuit. (See Circuit, Quadruple.)
Quantity. The term is applied to express arrangements of electrical connections for giving the largest possible amount of current.
Quantity, Electro-magnetic. The electro-magnetic current measured by its intensity for a second of time.
Quick-break. A break affected in an electric current by the employment of a quick-break switch.
Quickening. The amalgamating of the surface of a metallic object before electro-plating it with silver. This secures better adhesion of the deposit, and is done by dipping the article into a solution of mercurial salts—one part of mercuric nitrate to one hundred parts of water.
R
Radiant Energy. Energy existing in the luminiferous ether and exercised in wave transmission, creating light or sound. Radium possesses the highest form of radiant energy.
Radiate. To emit or send out in direct lines from a point or points, as radiating heat, light, or sound. The radiations are sent out in all directions from a central point, just as a stone thrown in a pond of still water will radiate waves or ripples from the central point.
Radiation. The travelling or motion of ether waves through space.
Radiator, Electric. A series of plates or wire-coils heated by current. They radiate heat and so warm the surrounding air.
Radiograph. A photographic picture taken by the X-ray process.
Receiver. In telephony or telegraphy, an instrument for receiving the message as distinguished from the instrument sending or transmitting the message.
The telephone piece held to the ear is the receiver.
Receiving End. The end of a line where the operative currents are received, as opposed to the end at which they are transmitted.
Receptacle. A device for the installation of an attachment or extension plug. Used in connection with electric-lighting circuits.
Recoil Kick. Reaction resulting from a disruptive discharge.
Recorder. In telegraphy, the receiving apparatus for recording the dot-and-dash signals on a strip or tape of paper.
Reduction. The influence exerted without apparent communication by a magnetic field or a charged mass upon neighboring bodies. The induction-coil is a simple example of this force. The current passes through the primary or inner coil about a core of soft iron, and in doing so it develops lines of force in the secondary or outer coils, although no current is flowing directly through them from a battery or dynamo.
Reduction Gear. A gear which acts to reduce a speed below that of a motor in full motion without lessening its motive force.
Refract. To break the natural course of light in an elastic medium. The rays of light, as they pass from a rare into a dense medium, are refracted.
Register, Electric. An apparatus for registering and recording the movements of employés about a building. Press-buttons are arranged throughout the building, and when a man passes a station he presses the button, and the time is recorded by the apparatus.
Regulator Magnet. (See Magnet, Regulator.)
Relay. A telegraphic or telephonic receiving instrument which opens and closes a local circuit through movements caused by the impulses of currents received. The relay battery may be very delicate so as to work with weak currents. The function of the relay is to open and close circuits for the admission of a new current to push on the sound or vibration to a more distant point. The main battery may be of any desired power.
Relay Connection. A connection used in telegraphy, including a local battery, with a short circuit, normally open, but closed at will by a switch and sounder, or other appliance. A very weak current will work the apparatus.
Relay, Ordinary. A relay that is not polarized.
Relay, Repeating. In telegraphy, a relay for repeating the signals through a second line.
Reluctance. Magnetic resistance.
Repeater. In telegraphy, an instrument for repeating the signals through a second line. It is virtually a relay which is controlled by the sender, and which, in turn, operates the rest of the main line. It is usually located at about the middle of the total distance covered.
Repeating-station. A telegraph station located on a long line, and occupying a position at the juncture of the sections into which the line is divided. The currents received through one section are repeated into the other sections by means of a repeater.
Repulsion, Electric. The tendency which exists between two bodies charged alike to mutually repel each other.
Residual Charge. (See Charge, Residual.)
Resilience. The power to spring back to a former position. Electricity is resilient, although its elasticity cannot be measured accurately.
Resin. A solid inflammable substance or gum, and a good non-conductor in electrical work. It is the product obtained by distilling the sap of the pitch-pine. The name is also applied to the product of distilling the sap of other trees. Common resin, shellac, lac, Dragon’s-blood, and other substances of a similar nature are resins. They are all dielectrics, and the source of negative frictional electricity when rubbed with cotton, wool, flannel, silk, or fur.
Resistance. That quality of an electric conductor in virtue of which it opposes the passage of an electric current, causing the disappearance or modification of electro-motive force, and converting electric energy into heat energy.
Resistance-box. A box filled with resistance-coils connected in series and provided with a switch, so that any number of the coils may be cut out.
Resistance, Carbon. A resistance composed of carbon as a substitute for a coil of wire. Carbon rods are placed close together having an air space between them, with alternate ends connected. Piles may be built up of carbon plates, whose resistance is made to vary by changing the pressure.
Resistance-coil. A coil of wire metal or other substances having the power to resist a current of electricity.
A coil of wire used to measure an unknown resistance by virtue of its own known resistance. (See also Coil, Resistance.)
Resistance, Dielectric. (See Dielectric Resistance.)
Resistance, Electrolytic. The resistance of an electrolyte to the passage of a current decomposing it. It is almost entirely due to electrolysis, and is intensified by counter-electro-motive force. When a current of a voltage so low as not to decompose an electrolyte is passed through the latter, the resistance appears very high and sometimes almost infinite. If the voltage is increased until the electrolyte is decomposed the resistance suddenly drops to a point lower than the true resistance.
Resistance, Internal. The resistance of a battery, or generator, in an electric circuit as distinguished from the resistance of the rest of the circuit.
Resistance, Liquid. A liquid of varying specific gravity used to create resistance to the passage of the electric current.
Resistance effected by the use of liquid through which a current must pass to complete a circuit.
Resistance, Metallic. The resistance of metals to the electric current.
German-silver resistance as distinguished from that of water, carbon, or other substances.
Resistance, Ohmic. True resistance measured in ohms as distinguished from counter electro-motive force. (See also Ohmic Resistance.)
Resistance, Spurious. The counter-electro-motive force. In its effect of opposing a current and in resisting its formation it differs from true resistance. True resistance diminishes current strength, absorbs energy, and develops heat. Spurious resistance opposes and diminishes a current without absorption of energy or production of heat.
Resistance, Standard. A known resistance employed to determine unknown resistances by comparison.
Resistance, True. The true resistance measured in ohms as distinguished from counter-electro-motive force.
Resonator, Electric. A small, open electric circuit with ends nearly touching. When exposed to electric resonance, or to a sympathetic electric oscillating discharge, a spark passes across the gap. The spark is due to inductance in the resonator.
Retentiveness. That property which enables steel to retain its magnetism.
Return. A line or conductor which carries current back to its starting-point after it has traversed a circuit. The best definition of a return is a circuit on which no new apparatus is installed.
Return-circuit. (See Circuit, Return.)
Return-circuit, Railway. A grounded circuit used in trolley systems for ground returns through the tracks, they being joined by links or flexible wires so as to form perfect conductors. It is the negative side of the system, the positive being in the overhead or underground feed-wire or rail.
Reversibility. The principle by which any form of generator for producing a given form of energy may be reversed to absorb energy. The dynamo of the reversible type driven to generate current may be reversed and will develop power if a current is run through it.
Rheostat. An adjustable resistance. An apparatus for changing the resistance, without opening the circuit, by throwing a switch-bar across contact points.
Rod Clamp. A clamp used in the lamp rod of an arc-light to hold the carbon.
Röntgen Effects. Phenomena obtained by the use of the X or Röntgen rays.
Röntgen-ray Screen. A screen whose surface is covered with fluorescent material for the purpose of receiving and displaying the Röntgen image.
Röntgen Rays. A peculiar form of light radiation discovered by Röntgen, and which is emitted from that portion of a high vacuum tube upon which the kathode rays fall.
Rotary Magnetic Field. (See Magnetic Field, Rotary.)
Ruhmkorff Coil. (See Coil, Ruhmkorff.)
S
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.
T
Table-push. A push-button connected with a call-bell and fixed on a table for convenience in using.
Tamadine. A form of cellulose used for making the filaments of incandescent lamps. The material is cut into proper shapes, carbonized, and flashed.
Tangent Galvanometer. (See Galvanometer, Tangent.)
Tape, Insulating. Prepared tape used in covering the bared ends of wires or joints.
Tap-wires. The conductors in trolley systems that at stated intervals, take the current from the mains and supply it to the bare feed-wires.
Telegraph. A system of electric communication invented by S. F. B. Morse, in which the dot-and-dash characters are used. There are various modifications of the system—double (or duplex), multiplex, and quadruplex—by means of which a number of messages may be sent out over the same wires at one time. Communication from place to place is had over wires mounted on poles, or by underground or submarine cables.
Telegraphy, Wireless. A system of telegraphy carried on without the aid of wires, using instead the ether waves of the atmosphere to conduct the vibrations overhead, and the ground, or earth, as a return. The present limit of its working is about four thousand miles.
Telephone. An instrument and apparatus for the transmission of articulate speech by the electric current. A magnet is encased in a tube and is encircled at one end by a coil of fine, insulated wire. A diaphragm of thin iron is fixed in front of the coil and close to the end of the magnet. The ends of the coil-wires are connected with a line, at the other end of which another and similar instrument is installed. The voice causes the sending diaphragm to vibrate, and these waves are transmitted to the other instrument, where they can be heard through contra-vibrations of the receiving diaphragm.
Telephone, Long-distance. A telephone of modern construction, in which the sound-recording mechanism is so sensitive as to make the vibrations of the voice audible at long distances. It will work satisfactorily at one thousand or even fifteen hundred miles.
Terminal. The end of any open electric circuit, or of any electric apparatus, as the electrodes of a battery.
Thermostat, Electric. An apparatus similar in some respects to a thermometer, and used for closing an electric circuit when the latter becomes heated. It is used in connection with automatic fire-alarms to give warning of fire. For this purpose the metal coil is arranged to close the contact at a temperature of 125° F. It usually consists of a compound strip of metal wound in the form of a spiral and fastened at one end. To this end one terminal of a circuit is connected. The expansion of the coil causes its loose end to touch a contact-point and close the circuit.
Third Rail. A railway motive system which employs a third rail instead of an overhead trolley feed-wire. The rail is laid on or under the surface of the ground and properly insulated. A shoe from the car bears on the rail and takes up the current.
Three-wire Circuit. A system invented by Edison for the distribution, from two dynamos, of current for multiple arc or constant potential service. One wire or lead starts from the positive pole of one dynamo, another from the negative pole of the other dynamo, and between the two dynamos the central or neutral lead is made fast.