Part 2 — APPENDIX A DICTIONARY OF ELECTRICAL TERMS AND PHRASES

Everybody is interested in electricity, but the ordinary reader, and particularly the boy who attempts to use this manual intelligently, will come across many technical words and terms that require explanation. It would be impossible to incorporate all needful definitions in the text proper, and the reader is therefore referred to the technical dictionary on the succeeding pages.

Care has been taken in its compilation to make the definitions complete, simple, and concise. Some of the more advanced technical terms have been purposely omitted as not necessary in a book dealing with elementary principles. The student in the higher branches of the science will consult, of course, the more advanced text-books. But for our practical purposes this elementary dictionary should answer every requirement. To read it over is an education in itself, and the young experimenter in electrical science should always refer to it when he comes across a word or phrase that he does not fully understand.

A

A. An abbreviation for the word anode.

Absolute. Complete by itself. In quantities it refers to fixed units. A galvanometer gives absolute readings if it is graduated to read direct amperes or volts. An absolute vacuum is one in which all residual gases are exhausted; an absolute void is the theoretical consequent. The absolute unit of current is measured in one, two, three, or more amperes or volts.

A-C. An abbreviation expressing alternating current.

Acceleration. The rate of change in velocity.

The increase or decrease of motion when acted upon by the electric current.

Accumulator. A term applied to a secondary battery, commonly called a storage-battery.

Accumulator, Electrostatic. (See Electrostatic Accumulator.)

Accumulator, Storage. A storage-battery.

Acid. A compound of hydrogen capable of uniting with a base to form salts.

Sour, resembling vinegar.

A sharp, biting fluid.

Acidometer. A hydrometer used to determine the gravity of acids. It is employed chiefly in running storage-batteries to determine when the charge is complete.

Adapter. A screw-coupling to engage with different size screws on either end, and used chiefly to connect incandescent lamps to gas-fixtures.

Adherence. The attraction between surfaces of iron due to electro-magnetic action. The term is used in connection with electric brakes—electro-magnetic adherence.

Adjustment. Any change in an apparatus rendering it more efficient and correct in its work.

Aerial Conductor. A wire or electric conductor carried over housetops or poles, or otherwise suspended in the air, as distinguished from underground or submarine conductors.

Affinity. The attraction of atoms and molecules for each other, due to chemical or electrical action.

Air-condenser. A static condenser whose dielectric is air.

Air-line Wire. In telegraphy that portion of the line-wire which is strung on poles and carried through the air.

Alarm, Burglar. A system of circuits with an alarm-bell, the wires of which extend over a house or building, connecting the windows and doors with the annunciator.

Alarm, Electric. An appliance for calling attention, generally through the ringing of a bell or the operating of a horn.

Alarm, Fire and Heat. An expansion apparatus that automatically closes a circuit and rings a bell.

Alive, or “Live.” A term applied to a wire or circuit that is charged with electricity. A “live” wire.

Active circuits or wires.

Alloy. Any mixture of two or more metals making a scientific compound. For example: copper and zinc to form brass; copper, tin, and zinc to form bronze; copper, nickel, and zinc to form German-silver.

Alternating Current. (See Current, Alternating.)

Alternating Current-power. Electrical distribution employing the alternating current from dynamos or converters.

Alternation. A change in the direction of a current; to and fro. Alternations may take place with a frequency ranging from 500 to 10,000 or more vibrations per second.

Alternator. An electric generator-dynamo supplying an alternating current.

Amalgam. A combination of mercury with any other metal.

Amalgamation. The application of mercury to a metal, the surface of which has been cleansed with acid. Mercury will adhere to all metals, except iron and steel, and particularly to zinc, which is treated with mercury to retard the corrosive action of acid on its surface.

Amber. A fossil resin, valuable only in frictional electric experiments. Most of it is gathered on the shores of the Baltic Sea between Königsberg and Memel. It is also found in small quantities at Gay Head, Massachusetts, and in the New Jersey green sand. When rubbed with a cloth it becomes excited with negative electricity.

Ammeter. The commercial name for an ampere-meter. An instrument designed to show, by direct reading, the number of amperes of current which are passing through a circuit.

Ampere. The practical unit of electric current strength. It is the measure of the current produced by an electro-motive force of one volt through a resistance of one ohm.

Ampere-currents. The currents theoretically assumed to be the cause of magnetism.

Ampere-hour. The quantity of electricity passed by a current of one ampere in one hour. It is used by electric light and power companies as the unit of energy supplied by them, and on which they base their reckoning for measuring the charges for current consumed.

Ampere-ring. A conductor forming a ring or circle. Used in electric balances for measuring current.

Animal Electricity. A form of electricity of high tension generated in certain animal systems—the Torpedo, Gymnotus, and Célurus. The shocks given by these fish, and particularly the electric eel, are often very severe.

Annealing. The process of softening yellow metals by heating them to a cherry redness, then allowing them to cool gradually in the air.

Electric annealing is done by passing a current through the body to be annealed, and heating it to redness; then allowing it to cool gradually.

Annunciator. An apparatus for giving a call from one place to another, as from a living-room to a hotel office, or for designating a window or door that may have been opened when protected by a burglar-alarm.

Annunciator-drop. The little shutter which is dropped by some forms of annunciators, and whose fall discloses a number or letter, designating the location from which the call was sent.

Anode. The positive terminal in a broken, metallic, or true conducting circuit.

The terminal connected to the carbon-plate of a battery, or to its equivalent in any other form of electric generator, such as a dynamo or a voltaic pile.

The copper, nickel, gold, or silver plates hung in an electro-plating bath, and from which the metal is supplied to fill the deficiency made by the electro-deposition of metal on the kathode or negative object in the bath.

Anti-hum. A shackle inserted directly in a line-wire near a pole. It is provided with a washer or cushion of rubber to take up the vibrations of a wire. To continue the circuit a bridle, or curved piece of wire, is connected with the line-wires that are attached to the shackle.

Arc. A term applied to an electric current flowing from carbon to carbon, or from metals separated by a short gap, as in the arc street-lamps.

The original arc was produced by two vertical rods, through which the current passed up and down. When not in action the upper ends touched, but as the current flowed the ends were separated, so that the current, passing up one carbon across the gap and down the other, formed the segment of a circle in jumping from one tip to the other.

An arc of electric flame is of brilliant and dazzling whiteness. The voltaic arc is the source of the most intense heat and light yet produced by man. The light is due principally to the incandescence of the ends of carbon-pencils, when a current of sufficient strength is passing through them and jumping over the gap. Undoubtedly the transferred carbon particles have much to do with its formation. The conductivity of the intervening air and the intense heating to which it is subjected, together with its coefficient of resistance, are other factors in the brilliant light produced.

Arc-lamp. An electric lamp which derives its light from the voltaic arc, by means of carbon-pencils and a current jumping from one to the other.

Arc, Quiet. An arc free from the hissing sound so common in arc-lights.

Arc, Simple. A voltaic arc produced between only two electrodes.

Armature. A body of iron or other material susceptible to magnetization, and which is placed on or near the poles of a magnet.

That part of an electric mechanism which by magnetism is drawn to or repelled from a magnet.

The core of a dynamo or motor which revolves within the field magnets, and which is the active principle in the generation of current by mechanical means, or in the distribution of power through electrical influence. Armatures are sometimes made of steel, and are permanent magnets. These are used in magneto-generators, telegraph instruments, and other apparatus.

Armature-bar. An armature in a dynamo or motor whose winding is made up of conductors in the form of bars.

Armature-coil. The insulated wire wound around the core of the armature of an electric current-generator or motor.

Armature-core. The central mass of iron on which the insulated wire is wound; it is rotated in the field of an electric current-generator or motor.

Armored. Protected by armor; as cables may be surrounded by a proper sheathing to guard them from injury.

Astatic. Having no magnetic directive tendency, the latter being a general consequent of the earth’s magnetism.

Astatic Circuit. (See Circuit, Astatic.)

Astatic Couple. (See Couple, Astatic.)

Astatic Needle. A combination of two magnetic needles so adjusted as to have as slight directive tendency as possible. The combination is generally made up of two needles arranged one above the other with the poles in opposite directions—commonly called “Nobili’s Pair.” These needles require but a slight electro-force to turn them one way or the other, and are used in astatic galvanometers.

Atmospheric Electricity. (See Electricity, Atmospheric.)

Atom. The ultimate particle or division of an elementary substance. Electricity is largely responsible for the presence of atoms in the atmosphere.

Atomic Attraction. The attraction of atoms for each other. Principally due to electric disturbance.

Attraction. The tendency to approach and adhere or cohere which is shown in all forms of matter. It includes gravitation, cohesion, adhesion, chemical affinity, electro-magnetic and dynamic attraction.

Aurora. A luminous electric display seen in the northern heavens. It is commonly thought to be the electric discharges of the earth into the atmosphere, due to revolution of the former and to the heat produced at the equator. As compared to the static machine for generating frictional electricity, the earth represents the revolving wheel gathering the current and discharging it at the poles.

Automatic Cut-out. An electro-magnetic switch introduced into a circuit, so as to break the circuit of the latter should it become overloaded with current; it also acts in the event of a mechanical interruption.

Automatic Regulation. A speed regulator worked by electricity so that a uniform flow of current may be secured automatically.

Ayrton’s Condenser. This is a pile of glass plates separated by small pieces of glass at the four comers, so that the plates cannot touch each other. Tin-foil is pasted on both sides of every plate, and the two coatings are connected. The tin-foil on each second plate is smaller in area than that on the others, and the plates are connected in two sets, negative and positive. In this construction it will be seen that the glass is not the dielectric proper, but acts only as the plane to which the tin-foil is pasted. One set of plates are connected to a binding-post by strips of tin-foil, and the other set are connected to another binding-post in a similar manner.

B

B. An abbreviation for Beaumé, the inventor of the hydrometer scale. Thus, in speaking of the gravity of fluids, 20° B. means twenty degrees Beaumé.

Back Induction. A demagnetizing force produced in a dynamo when a lead is given to the brushes. (See also Induction, Back.)

Back Shock. A lightning stroke received after the main discharge. It is caused by a charge induced in neighboring surfaces by the main discharge.

Bad Earth. A poor ground connection, or one having comparatively strong electrical resistance.

Balance. A proper adjustment between the apparatus and the electro-motive force, thus securing the best possible results.

B. & S. W-G. Abbreviations for Brown & Sharp and wire-gauge, and referring to the sizes of wire and sheet-metal thicknesses that are considered standards in America.

Bar-armature. An armature in which the conductors are constructed of bars.

Bar-magnet. One whose core presents the appearance of a straight bar, or rod, without curve or bend.

Bare-carbons. Electric light carbons whose surfaces are not electro-plated with copper.

Barometer. An apparatus for measuring the pressure exerted by the atmosphere. It consists of a glass tube 31 inches long, closed at one end, filled with mercury, and then inverted, with its open end immersed in a cistern of mercury. The column of mercury falls to a height proportional to the pressure of the atmosphere. At the sea-level it ranges from 30 to 31 inches.

Bar-windings. The windings of an armature constructed of copper bars.

Bath. In electro-plating, the solution or electrolyte used for depositing metal on the object to be plated. It may be a solution of copper, silver, nickel, or other metal.

In electro-therapeutics it is a bath of water with suitable electrodes and connections for treating patients with electricity.

Bath-stripping. A solution used for stripping or removing the metal plating from an object.

Batten. A strip of wood grooved longitudinally, in which electric light or power wires are set. The grooved strip is screwed to the wall, the wires being laid in the grooves, and then covered with a thin wooden strip fastened on with small nails.

Battery. A combination of parts, or elements, for the production of electrical action.

A number of cells connected parallel or in series for the generation of electricity. Under this heading there are at least one hundred different kinds. Nowadays the dynamo is the cheap and efficient generator of electricity.

Battery Cell, Elements of. The plates of zinc and carbon, or of zinc and copper, in a cell are called elements. The plate unattacked by the solution, such as the carbon or copper, is the negative element, while the one attacked and corroded by the electrolyte is the positive.

Battery, Dry. A form of open circuit cell in which the electrolyte is made practically solid, so that the cell may be placed in any position. A zinc cup is filled with the electrolyte and a carbon-rod placed in the middle, care being taken to avoid contact between cup and carbon at the bottom of the cell. The gelatinous chemical mass is then packed in closely about the carbon, so as to nearly fill the cup. A capping of asphaltum, wax, or other non-conducting and sealing material is placed over the electrolyte, and this hardens about the carbon and around the top inner edge of the zinc cup. The latter becomes the positive pole, the carbon the negative. Binding-posts, or connections, may be attached to the zinc and carbon to facilitate connections.

Battery, Galvanic. The old name for a voltaic battery.

Battery, Gravity. A battery in which the separation of fluids is obtained through their difference in specific gravity—for example, the bluestone cell. The sulphate of copper solution, being the more dense, goes to the bottom, while the zinc solution stays at the top. In its action the acid at the top corrodes the zinc, while at the bottom the solution is decomposed and deposits metallic copper on the thin copper plates.

Battery, Leclanché. An open circuit battery consisting of a jar, a porous cup, and the carbon and zinc elements, the electrolyte of which is a solution of ammonium chloride (sal-ammoniac). The carbon plate is placed in the porous cup, and packed in with a mixture of powdered manganese binoxide and graphite, to serve as a depolarizer. A half-saturated solution of sal-ammoniac is placed in the outer jar, and a rod of zinc suspended in it. Another form of the battery is to omit the porous cup and use twice the bulk of carbon, both elements being suspended in the one solution of sal-ammoniac; this form of battery is used for open-circuit work only, such as bells, buzzers, and annunciators. It is not adapted for lights, power, or plating purposes.

Battery Mud. A deposit of mud-like character which forms at the bottom of gravity batteries, and which consists of metallic copper precipitated by the zinc. It only occurs where wasteful action has taken place.

Battery of Dynamos. A term used in speaking of a number of dynamos coupled to supply the same circuit. They may be coupled in series or parallel.

Battery, Plunge. A battery in a cabinet or frame, so arranged that the active plates can be removed or raised out of the solutions. This is usually accomplished by having the plates attached to a movable frame which, by means of a ratchet-shaft and chains, can be raised or lowered. Its object is to prevent the corrosion of the plates when not in use.

Battery, Primary. A voltaic cell or battery generating electric energy by direct consumption of material. The ordinary voltaic cell, or galvanic battery, is a primary battery.

Battery, Secondary. A storage-battery, an accumulator.

Battery Solution. The active excitant liquid, or electrolyte, placed within a cell to corrode the positive element. Also called Electropoion.

Battery, Storage. A secondary battery; an accumulator; a battery which accumulates electricity generated by primary cells or a dynamo.

Battery-gauge. A galvanometer used for testing batteries and connections. It is usually small in size, and may be carried in a pocket.

Battery-jar. A glass, earthen, or lead vessel which contains the fluids and elements of each separate cell of a battery.

Baumé Hydrometer. (See Hydrometer, Baumé.)

Becquerel Ray and Radiation. An invisible ray discovered by Becquerel, which is given out by some compounds and chemicals—notably uranium—and which has the power to penetrate many opaque bodies and objects impenetrable to the actinic rays of ordinary light. These rays are used chiefly in connection with the photographic dry-plate.

Bell, Electric. A bell rung by electricity. The current excites an electro-magnet, attracting or releasing an armature which is attached to a vibrating or pivoted arm, on the end of which the knocker is fastened.

Bichromate of Potash. A strong, yellowish-red chemical, used chiefly in battery fluids and electrolytes.

Bifilar Winding. The method followed in winding resistance-coils. To prevent them from creating fields of force, the wire is doubled and the looped end started in the coil. Since the current passes in opposite senses in the two lays of the winding, no field of force is produced.

Binding. Unattached wire wound round armature-coils to hold them in place.

Binding-post. An arrangement for receiving the loose ends of wires in an electric circuit and securing them, by means of screws, so that perfect contact will be the result.

Bi-polar. Possessing two poles.

Bi-telephone. A pair of telephones arranged with a curved connecting arm or spring so that they can be simultaneously applied to both ears.

Blasting, Electric. The ignition of a blasting charge of powder, dynamite, or other high explosive by an electric spark, or by the heating, to red or white heat, of a thin wire imbedded in the explosive.

Block System. A system of signalling on railroads. Signal-posts are arranged at stated spaces, and on these signals appear automatically, showing the location of trains to the engineers of trains in the rear.

Bluestone. A trade name for sulphate of copper in a crystallized state.

Bobbin. A spool of wood or other non-conducting substance wound with insulated wire. In a tangent galvanometer the bobbin becomes a ring with a channel to receive the wire.

Boiling. In secondary, or storage, batteries the escaping of hydrogen and oxygen gases, when the battery is fully charged, resembles water boiling.

Bonded Rails. Rails used in an electric traction system, and which are linked or connected together to form a perfect circuit. Used principally in the third-rail system.

Brake, Electro-magnetic. A brake to stop the wheels of a moving car. It consists of a shoe, or ring, which by magnetic force is drawn against a rotating wheel to stop its revolution.

Branch. A conductor which leads off from a main line to distribute current locally.

Brassing. A process of electro-depositing brass in a bath containing both copper and zinc. A plate of brass is used as an anode.

Brazing, Electric. A process in which the spelter is melted by electric current, so that the two parts are united as one.

Break. A point where an electric conductor is broken, as by a switch or a cut-out.

Bridge. A special bar of copper connecting the dynamos with the bus wire in electric lighting or power stations.

Bronzing. The deposition of bronze by electro-plating methods. The mixture is of copper and tin, and a cast bronze plate is used as an anode.

Brush. A term applied to the pieces of copper, carbon, or other conducting medium in dynamos and motors, that bear against the cylindrical surface of the commutators to collect or feed in the current.

Bug. Any fault or trouble in the connections or workings of an electrical apparatus. The term originated in quadruplex telegraphy, and probably had some connection with the Edison bug-killer that he invented when a boy.

Buoy, Electric. A buoy to indicate dangerous channels in harbors and to mark wrecks and reefs. It is provided with an electric light at night, and with a gong or an electric horn by day.

Burner, Electric. A gas-burner so arranged that the flame may be lighted by electricity operated by a push-button at some distance from the fixture, or, close at hand, by means of a chain or pull-string.

Burning. In a dynamo, the improper contact of brushes and commutator, whereby a spark is produced and an arc formed which generates heat and causes the metal parts to burn.

Bus-rod. A copper conductor used in power-plants to receive the current from the battery of dynamos. The distributing leads are connected to these rods.

Butt-joint. A joint made by bringing the ends of wires together so that the ends butt. They are then soldered or brazed.

Button, Electric. A form of switch that is operated by pushing a button mounted on a suitable base. Used principally for ringing bells, operating lights, etc.

Buzzer. An electric alarm, or call, produced by the rapid vibration of an armature acted upon by electro-magnetism. The sound is magnified by enclosing the mechanism in a resonant box.

An apparatus resembling an electric bell minus the bell and clapper. The buzzer is used in places where the loud ring of a bell would be a nuisance.

C

C. An abbreviation for centigrade when speaking of thermal temperature. In chemistry the centigrade scale is used extensively, but in air temperatures the Fahrenheit scale is universally employed.

Cable, Aerial. A cable that contains a number of wires separately insulated, the entire mass being protected by an external insulation. It is suspended in the air from pole to pole, and sometimes its weight is so great that a supporting wire is carried along with it (usually overhead), the large cable being suspended from it by cable-hangers.

Cable Box. A box to receive cable ends and protect them; also, the box in which cable ends and line-wires are joined. Submarine cable boxes are usually near the ground, while telephone and telegraph cable boxes are mounted on poles, the cables running from the ground and up the poles to the boxes.

Cable-core. The conductors of a cable which make up its interior mass. For the convenience of linemen the wires are often insulated with different-colored materials so that testing is not necessary when making connections.

Cable-hanger. A metallic grip, usually of sheet metal, arranged to clasp two or more wires. It is fastened to the supporting wire by a hook and eye, or by small bolts with thumb-nuts.

Cable-head. A rectangular board equipped with binding-posts and fuse wires so that the connections may be made between the cable ends and the overhead or line-wires of a system.

Cables. An insulated electric conductor of large diameter, often protected by armor or metallic sheathing, and generally containing, or made up, of several separately insulated wires. Cables supply current to traction lines; power, through subterranean passages; communication, by submarine connection; and light, by overhead or underground conduits.

Call-bell. A bell that is rung by pressing a button, and which is operated by electricity.

Calling-drop. A drop-shutter which is worked by electricity in a telegraph or telephone exchange; it denotes the location from which the call was sent in. Small red incandescent lamps have taken the place of the drops in most of the large telephone exchanges, for they are noiseless and do not annoy the operators as the drops and buzzers did.

Candle-power. The amount of light given by the standard candle. The legal English and American standard is a sperm candle burning two grains a minute.

Candle, Standard. The standard of illuminating power; a flame which consumes two grains of sperm wax per minute, and produces a light of a brightness equal to one candle-power.

Caoutchouc. India-rubber. So named because originally its chief use was to erase or rub off pencil marks. It is a substance existing, in a thick fluid state, in the sap or juices of certain tropical trees and vines; it possesses a very high value as an insulator for wire and circuits. The unworked, crude rubber is called virgin gum, but after it is kneaded it is called masticated or pure gum rubber.

Capacity. A term used when speaking of the carrying power of a wire or circuit. The capacity of a wire, rod, bar, or other conductor is sufficient so long as the current does not heat it. Directly electric heat is generated, we speak of the conductor as being overloaded or having its capacity overtaxed.

Capacity of a Telegraph Conductor. The electric capacity may be identical in quality with that of any other conductor. In quantity it varies not only in different wires, but for the same wire under different conditions. A wire reacting through the surrounding air, or other dielectric, upon the earth represents one element of a condenser, the earth in general representing the other. A wire placed near the earth has greater capacity than one strung upon high poles, although the wires may be of identical length and size and of the same metal. The effect of high capacity is to retard the transmission of current, the low capacity facilitates transmission.

Capacity, Storage. In secondary batteries, the quantity of electric current they can supply, when fully charged, without exhaustion. This capacity is measured or reckoned in ampere-hours.

Carbon. One of the elements in graphitic form used as an electric-current conductor. It is the only substance which conducts electricity, and which cannot be melted with comparative ease by increase of current. It exists in three modifications—charcoal, graphite, and the diamond. In its graphitic form it is used as an electro-current conductor, as in batteries and arc-light electrodes, and as filaments in incandescent lamps. In arc-lamp use the carbons are usually electro-plated on the outside with a film of copper which acts as a better conductor.

Carbon, Artificial. Carbon-dust, powdered coke, or gas carbon is mixed with molasses, coal-tar, syrup, or some similar carbonaceous fluid, so that the mass is plastic. It can then be moulded or pressed into shapes, and heated to full redness for several hours by artificial or electric heat. For lamp-carbons the mixture is forced through a round die by heavy pressure, and is cut into suitable lengths, then fired or baked.

After removing and cooling, the carbons are sometimes dipped again into the fluid used for cementing the original mass and re-ignited. This process is termed “nourishing.” All carbon is a resisting medium, but at high temperature the resistance is only about one-third as great; that is, the current will pass through a red-hot carbon three times better than through the cold carbon; or a current of thirty amperes will be conducted as easily through a hot carbon as ten amperes through a cold one.

Carbon-cored. A carbon for arc-lamps, the core being of softer carbon than the outer surface. It is supposed to give a steadier light, and fixes the position of the arc.

Carbon-dioxide. A compound gas, or carbonic-acid gas. It is a dielectric.

Carbon-holders. In arc-lamps, the clamps arranged to hold the carbon-pencils.

Carbonization. The ignition of an organic substance in a closed vessel, so as to expel all constituents from it except the carbon.

A destructive distillation.

Carbon Resistance. (See Resistance, Carbon.)

Carbon Volatilization. In arc-lamps the heat is so intense that it is believed a part of the carbon-pencil is volatilized, as vapor, before being burned or oxidized by the oxygen of the air.

Carbons, Bare. (See Bare Carbons.)

Carrying Capacity. In a current-conductor, its carrying capacity up to the heating-point. It is expressed in amperes.

Cascade. The arrangement of a series of Leyden-jars in properly insulated stools, or supports, for accumulating frictional electricity. They are arranged in a manner somewhat similar to a battery of galvanic cells, the inner coating of one being connected to the outer coating of the next, and so on through the series.

Case-hardening, Electric. A process by which the surface of iron is converted into steel by applying a proper carbonaceous material to it while it is being heated by an electric current.

Cautery, Electric. An electro-surgical appliance for removing diseased parts or arresting hemorrhages. It takes the place of the knife or other cutting instrument. It is a loop of platinum wire heated to whiteness by an electric current.

C.C. An abbreviation commonly used for cubic-centimeter. It is usually written in small letters, as 50 c.c., meaning 50 cubic-centimeters.

Cell, Electrolytic. A vessel containing the electrolyte used for electro-plating.

Cell, Regenerated. A cell restored to its proper functions by a process of recharging.

Cell, Standard. Meaning the same as battery. The vessel, including its contents, in which electricity is generated.

Cell, Storage. Two plates of metal, or compounds of metal, whose chemical relations are changed by the passage of an electric current from one plate to the other through an electrolyte in which they are immersed.

Cements, Electrical. Cements of a non-conducting nature, such as marine glue and sticky compounds, used in electrical work.

Centrifugal Force. A diametric revolving force which throws a body away from its axis of rotation. A merry-go-round is a simple example of this force. The more rapidly the platform revolves the greater the tendency for those on it to be thrown off and out from the centre. The high velocity attained by the armatures in motors and dynamos would throw the wires out of place and cause them to rub against the surfaces of the field-magnets. Consequently, wire bands or binders are necessary to keep the coils of wire from spreading under the influence of the centrifugal force.

Charge. The quantity of electricity that is present on the surface of a body or conductor.

The component chemical parts that are employed to excite the elements of a cell in generating electric current.

Charge, Residual. After a Leyden-jar, or other condenser, has been discharged by the ordinary methods, a second discharge (of less amount) can be had after a few minutes’ waiting. This is due to what is known as the residual charge, and is connected in some way with the molecular distortion of the dielectric.

Chemical Change. When bodies unite so as to satisfy affinity, or to bring about the freeing of thermal or other energy, the union is usually accompanied by sensible heat or light. Sulphuric acid added to water produces heat; a match in burning produces light. Another form of chemical change is decomposition or separation (the reverse of combination), such as takes place in the voltaic-battery, the electro-plating bath, and other forms of electrolysis. This is not accompanied by heat or light, but by the evolution of electricity.

Chemical Element. (See Element, Chemical.)

Chemistry. The science which treats of the atomic and molecular relations of the elements and their chemical compounds. Chemistry is divided into many departments, but electro-chemistry treats only of the science wherein electricity plays an active part, such as batteries, electro-plating, and electro-metallurgy.

Choking-coil. (See Coil, Choking.)

Circle, Magic. A form of electro-magnet. It is a thick circle of round iron used in connection with a magnetized coil to illustrate electro-magnetic attraction.

Circuit. A conducting-path for electric currents. Properly speaking, a complete circuit has the ends joined, and includes a source of current, an apparatus, and other elements introduced in the path. When the circuit is complete it is called active. The term circuit is also applied to portions of a true circuit—as, an internal or external circuit.

Circuit, Astatic. A circuit so wound, with reference to the direction of the currents passing through it, that the terrestrial or other lines of force have no directive effect upon it.

Circuit-breaker. Any apparatus for opening and closing a circuit, such as switches, automatic cut-outs, lightning-arresters, and the like.

A ratchet-wheel engaged with a spring, or wire, which rests against the teeth. The current passes through the wire, the wheel, and axle. The wheel is revolved by a crank, and as the ratchets pass the spring, or wire, an instantaneous make-and-break occurs. The speed of the wheel regulates the frequency of the interruptions.

Circuit, External. A portion of the circuit not included within the generator, such as a secondary telegraph key and sounder.

Circuit, Grounded. A circuit in which the ground is used as a conductor. This is common in telegraph and telephone lines, particularly for short distances where the conductivity of the earth does not offer too much resistance.

Circuit, Incandescent. A circuit in which incandescent lamps are installed.

Circuit Indicator. A pocket-compass, galvanometer, or other device for indicating or detecting the condition of a wire, whether it is active or dead, and, if active, in which direction the current is flowing. It may also give a general idea of its strength.

Circuit, Internal. That portion of an electric circuit which is included within the generator.

Circuit Loop. A minor circuit introduced, in series, into another circuit by a switch or cut-out, so that it becomes a part of the main circuit.

Circuit, Main. a circuit or main line, includes the apparatus supplying current to it. Thus distinguished from a local circuit.

Circuit, Metallic. A circuit in which the current outside the generator passes through metal parts or wire, but not through the ground. Electric light and power lines are always metallic circuits. An electro-plating apparatus may be properly termed a metallic circuit, although a part of the circuit is formed by the electrolyte in the bath. The essential meaning of the words metallic circuit is that the earth does not form a part of the return circuit.

Circuit, Open. A circuit in which a switch has been opened to prevent the continuous flow of current, such as an electric-bell circuit, which normally remains open, and which is active only when the push-button is pressed, thereby closing the circuit and operating the bell. An open-circuit battery is one that remains inactive when the circuit is open.

Circuit, Parallel. A term signifying a multiple circuit.

Circuit, Quadruple. A single circuit capable of having four messages transmitted over it simultaneously—two in one direction, and two in the other.

Circuit, Return. In telegraphy the ground is used as the return circuit. It is also that portion of a circuit which leads from an apparatus back to the terminal of a dynamo or battery, usually the negative wire.

Circuit, Short. A connection between two parts of a circuit, causing the current to skip a great part of its appointed path. Short-circuits prevent the proper working of any electrical apparatus.

Circuit, Simple. A circuit containing a single generator, the proper wire for carrying the current, and a switch to operate it. An electric-bell line, a single telegraph line, or a direct telephone line are all simple circuits.

Clamp. A tool for grasping and holding the ends of wires while joining them.

The appliance for holding the carbon-pencils in arc-lamps.

Cleats. Blocks of wood, porcelain, or other insulating material used to hold wires against a wall or beam. They have one, two, and three notches at one side, for single, double, and three wire systems.

Clutch, Electric. A form of magnetic brake applied to car-wheels, the armatures of motors, and other revolving mechanism, whereby the current, passing through a coil, magnetizes a mass of cast-iron, and brings it to bear frictionally upon the moving parts of the mechanism.

Code, Cipher. A set of disconnected words which, in accordance with a prearranged key, stand for whole sentences and phrases. Commercially the system is used as a short-cut—ten words perhaps meaning what otherwise it would take forty or fifty words to express. It is used extensively in telegraphy, both as an abbreviated message and as a means for securing secrecy.

Coherer. Conducting particles constituting a semi-conducting bridge between two electrodes, and serving to detect electro-magnetic waves. The coherer in wireless telegraphy is understood to mean that form of radio-receiver which, being normally at high resistance, is, under the influence of Hertzian-waves, changed to a low resistance, thus becoming relatively a conductor. Tubes of various kinds have been used for this purpose. Within them is a filling of carbon granules, copper filings, nickel and silver filings, and other substances. Marconi’s coherer consists of a tube one and one-half inches long and one-twelfth inch internal diameter. This is filled with filings—90 per cent. of nickel, 10 per cent. of silver. A globule of mercury coats the outer surface of each grain with a thin film of the quicksilver. Into both ends a piece of pure silver wire is plugged. These latter are a quarter of an inch long, and fit the tube very accurately. The tube is thus sealed, and it is considered preferable to have a slight vacuum within it.

Coil. A strand of wire wound in circular form about a spool, a soft-iron core, or in layers, as a coil of rope.

An electro-magnetic generator.

A helix. (See also Induction, Resistance, Magnetizing.)

Coil, Choking. A form of resistance to regulate the flow of current. Any coil of insulated wire wound upon a laminated or divided iron core forms a choking-coil. In alternating-current work special choking-coils are used. They have a movable iron core, and by thrusting it in or out the power is increased or diminished, thus raising or lowering the lights, the same as gas is regulated.

Coil, Faradic. The name given to a medical induction-coil or faradic machine.

Coil, Induction. A coil in which the electro-motive force of a portion of a circuit is, by induction, made to produce higher or lower electro-motive forces in an adjacent circuit, or in a circuit a part of which adjoins the original circuit. There are three principal parts to all induction-coils—the core, the primary coil, and the secondary coil. The core is a mass of soft iron, cast or wrought, but preferably divided—for example, a bundle of rods or bars. The primary coil of comparatively larger wire is wound about this core, each layer being properly insulated and varnished, or coated with melted paraffine, to bind the wires. The secondary coil is of fine wire, and is wound about the primary coil. A great many turns of the fine wire are necessary, and care must be taken to properly insulate each layer and shellac the wires. The primary must be well insulated from the secondary coil, so as to prevent sparking, which would destroy the insulation. A make-and-break is operated by the primary coil, and is constructed upon the general form of an electric bell or buzzer movement. Extra currents which interfere with the action of an induction-coil are avoided by the use of a condenser. (See also Condenser.) The induction-coil produces a rapid succession of sparks which may spring across a gap of thirty or forty inches, according to the size of the coil. Induction-coils are used extensively in electric work, especially in telephone transmitters, wireless telegraphy, electric welding, and in the alternating-current system.

Coil, Magnetizing. A coil of insulated wire so wound that a well or aperture will be formed. Within this well a piece of steel is placed, so that an electric current, passing through the wires, will magnetize the steel; or a steel rod may be passed in and out of the hole several times while a strong current is travelling through the coil, thus magnetizing the rod.

Coil, Resistance. A coil so constructed that it will offer resistance to a steady current of too great electro-motive force for the safety of the apparatus. Generally the coil is made by doubling the wire without breaking it, then starting at the doubled end to wind it in coil or spring fashion. If the wire is too heavy to wind double, a single strand is wound on a square or triangular insulator in which notches are made. Then, alternately between the coils, the second strand is wound. The strands are joined at one end of the coil, but those at the other are left free for unions with other wires. (See also Resistance.)

Coil, Retarding. A choking-coil. A resistance-coil.

Coil, Ribbon. Instead of wire, flat, thin strips of sheet-metal are sometimes used for resistance-coils, doubled, as explained above. The wraps are insulated with sheet-mica, micanite, or asbestos, to prevent short-circuiting.

Coil, Ruhmkorff. A common type of induction-coil with a vibrator or circuit-breaker. Used with constant and direct current.

A step-up transformer with a circuit-breaker attachment.

Coils, Idle. Coils in a dynamo in which no electro-motive force is being generated or developed.

Coils that, through broken connections or short circuits, are inactive.

Column, Electric. An old name for the voltaic pile. The apparatus made up of a pile of disks of copper and zinc, separated by pieces of flannel wet with acidulated water.

Comb. A bar from which a number of teeth project like the teeth of a comb. It is used as a collector of electricity from the plate of a frictional electric machine.

Commutator. An apparatus used on motors and dynamos and induction-coils for changing the direction of currents. It is made in a variety of types, but usually in the shape of insulated bars closely packed about an armature shaft.

Commutator-bars. The metallic segments of a dynamo or motor-commutator.

Commutators, Quiet. Commutators that do not spark during the revolutions of the armature.

Compass. An apparatus for indicating the directive force of the earth upon the magnetic needle. It consists of a case covered with glass, in which a magnetized needle, normally pointing to the north, is balanced on a point at the centre. Under the needle a card is arranged on which the degrees or points of the compass are inscribed. A valuable instrument in electrical work, magnetism, etc.

Compass, Liquid. A form of marine compass. The needle is attached to a card or disk which floats in alcohol or other spirits, so as to check undue oscillation.

Compass, Mariners’. A compass in which the needle is attached to a card that rotates in pointing to the north. A mark, called the “lubber’s mark,” is made upon the case, and this is in line with the ship’s keel, so that a glance at the card will indicate the direction in which the ship is headed.

Compass, Spirit. A form of mariners’ compass in which the bowl, or case, is sealed and filled with alcohol. The compass-card works as a spindle, and, by a series of air compartments, floats on the alcohol. The friction of the pivot is thereby greatly diminished, making the compass a very sensitive one.

Compass, Standard. A compass employed as a standard by which to compare other compasses.

Condenser. An appliance for storing up electro-static charges; it is also called a static accumulator. The telegraphic condenser consists of a box packed full of sheets of tin-foil having a sheet of paraffined paper or sheet-mica between every two sheets. The alternate sheets of tin-foil are connected together, and each set has its binding-post. (See also Electrostatic Accumulator.)

Condenser, Air. (See Air-condenser.)

Condenser, Ayrton’s. (See Ayrton’s Condenser.)

Condenser-plate. (See Plate, Condenser.)

Condenser, Sliding. An apparatus in the form of a Leyden-jar whose coatings can be slid past each other to diminish or increase the face area, and also to diminish or increase the capacity of the condenser.

Conductance. The conducting power of a mass of material, varying according to its shape and dimensions. The cylindrical or round conductor is the best type for the conveyance of electric currents.

Conduction. The transmission of electricity through an immobile medium, such as a wire, or rod, or a bar.

Conductivity. Ability to conduct electric currents. The conductivity of a wire is its power to conduct or transmit a current. Glass has no conductivity, and it is therefore a non-conductor.

Conductivity, Variable. The change in the conducting or transmitting powers of metals and substances under different temperatures. Hot metal conducts an electric current better than cold. A hot carbon-pencil in an arc-light conducts the current better than when the light is first started, for as it warms up under the influence of the arc-flame the current passes more freely. Five minutes after the current is turned on the lamps in the circuit give a steady light, and do not sputter as when they first start up.

Conductor. Anything which permits the passage of electric current. The term conductor is a relative one, and, excepting a vacuum, there is probably no substance that has not some conductive power. Metals, beginning with silver, are the best conductors, liquids next, glass the worst. The ether, or air, is a conductor of sound and electric vibratory disturbances, but not in the same sense as the ground. The air conducts frictional electricity, while the ground acts as a conductor for the galvanic current, or “current electricity.” By this last term is meant electricity which flows continually, instead of discharging all at once, with an accompanying spark or flash.

Conductor, Overhead. Overhead electric lines, wires or cables, for conducting current. Generally poles are erected for this purpose.

Conductor, Prime. A cylindrical or spherical body with no points or angles, but rounded everywhere and generally of metal. If made of other material, such as wood, glass, or composition, its entire surface is rendered conductive by being covered with sheet-metal, such as tin-foil, gold-leaf or tinsel, applied to it with paste, shellac, or glue. A prime conductor should be mounted on an insulated stand; it is employed to collect and retain frictional electricity generated by a static machine.

Conductor, Underground. An insulated conductor which is placed under the surface of the earth, passing through conduits.

Connect. The act of bringing two ends of wire together, either temporarily or permanently. Bringing one end of a conductor into contact with another so as to establish an electric connection.

Connector. A sleeve, with screws or other clamping device, into which the ends of wires or rods may be passed and held securely. A binding-post and spring-jack comes under this head.

Contact. The electrical union of two conductors, whether temporary or permanent. It may be established by touching the ends or terminals of a circuit through the agency of a push-button, a telegraph-key, an electric switch, etc.

Contact-breaker. (The same as Circuit-breaker, which see.)

Contact, Loose. A contact formed by two or several surfaces imposed one upon another and held by their weight alone.

Contact-point. A point, or stud, often of silver or platinum, arranged to come into touch with a contact-spring, such as the vibrating armature of an electric bell.

Contact-spring. A spring connected at one end of a lead and arranged to press against another spring or plate, so that a plug may be inserted between the contact-points.

Controller. The lever or handle on the switch-board of a resistance-coil, by means of which electric current is let in or kept out of a circuit.

Controlling Force. In galvanometers and similar instruments, the force used to bring the needle or indicator back to zero.

Converter. An induction-coil used with the alternating current for changing the potential difference and inverting the available current. High alternating voltage may be converted into lower direct-current voltage, thereby increasing the amperage or current. A converter consists of a core of thin iron sheets, wound with a primary coil of fine insulated wire, with many convolutions or turns. Also, a secondary coil made up of coarse insulated wire with fewer convolutions. The coil may be jacketed with iron to increase the permanence.

Converter, Rotary. A combined motor and dynamo whose function is to transform a current of high or low voltage (A-C., or D-C.) into any other kind of current desired.

Convolution. The state of being convolved; a turn, wrap, fold, or whorl. A clock-spring is a familiar example.

Copper-bath. A solution of sulphate of copper used in electro-plating, electrotyping, and copper-refining by electricity.

Cord, Flexible. A flexible-wire conductor made up of many strands of fine wire and properly insulated so that it may be easily twisted, bent, or wrapped. Flexible wire is used as the conductors for portable electric lights, push-buttons, medical coils, etc.

Core. The iron mass (generally located in the centre of a coil or helix) which becomes highly magnetic when a current is flowing around it, but which looses its magnetism immediately that the current ceases to flow.

A conductor or the conductors of an electric cable made up of a single strand or many strands laid together and twisted. These may be of bare metal, or each one insulated from the others.

Core-disks. Disks of thin wire, for building up armature-cores. The usual form of a core is round or cylindrical. A number of thin disks, or laminations, of iron strung upon the central shaft, and pressed firmly together by the end-nuts or keys. This arrangement gives a cylinder as a base on which to wind the insulated wire that forms a part of the armature.

Core-disks, Pierced. Core-disks for an armature of a motor or dynamo, which have been pierced or bored out around the periphery. Tubes of insulating material, such as fibre, rubber, or paraffined paper, are inserted in the holes and through these the windings of wire are carried. The coils are thus imbedded in the solid mass of iron, and are protected from eddy currents; also they act to reduce the reluctance of the air-gaps. This arrangement is very good, from a mechanical point of view, but in practice its use is confined to small motors only, and dynamos generating under one hundred volts.

Core-disks, Toothed. Core-disks of an armature or motor where notches are cut from the periphery. When they are locked together, to form the armature-core, the coils of wire lie in the grooves formed by a number of the disks bound together. This construction reduces the actual air-gaps and keeps the coils equally spaced.

Core, Laminated. The core of an armature, an induction-coil, a converter, or any similar piece of apparatus, which is made up of plates or disks, insulated more or less perfectly from one another by means of mica or paraffined paper. The object of laminations is to prevent the formation of Foucault currents. A core built up of disks is sometimes called a radially laminated core.

Core, Ring. A dynamo or motor armature-core which forms a complete ring.

Core, Stranded. The core of a cable, or a conducting core made up of a number of separate wires or strands laid or twisted together.

Core, Tubular. Tubes used as cores for electro-magnets, and also to produce small magnetizing power. Tubular cores are nearly as efficient as solid ones in straight magnets, because the principal reluctance is due to the air-path. On increasing the current, however, the tubular core becomes less efficient.

Coulomb. The practical unit of electrical quantity. It is the quantity passed by a current of one ampere intensity in one second.

Couple. The combination of two electrodes and a liquid, the electrodes being immersed in the latter, and being acted on differentially by the liquid. This combination constitutes a source of electro-motive force, and, consequently of current, and is called the galvanic or voltaic cell or battery.

Couple, Astatic.. A term sometimes applied to astatic needles when working in pairs.

Coupling. The union of cells or generators constituting a battery; the volume of current, or electro-motive force, is thereby increased.

C. P. An abbreviation for “candle power”; also meaning “chemically pure,” when speaking of chemicals.

Crater. The depression that forms in the positive carbon of a voltaic-arc.

Creeping. A phenomena met with in solution batteries. The electrolyte creeps up the sides of the containing jar and evaporates, leaving a deposit of salts. Still more solution creeps up through the salts until it gets clear to the top and runs over. To prevent this the tops of the jars should be brushed with hot paraffine for a distance of two inches from the upper edge. The salts will not form on paraffine. Oil is sometimes poured on the top of the battery solution, but this affects the elements if it touches them, and makes their surfaces non-conducting.

Crucible, Electric. A crucible for melting refractory substances, or for reducing ores by means of the electric arc produced within it. Probably the result obtained is due more to current incandescence than to the action of the arc.

Crystallization, Electric. Under proper conditions many substances and liquids take a crystalline form. When such action is brought about by means of electricity the term electric crystallization may be applied to the phenomenon. A solution of nitrate of silver, when decomposed by a current, will give crystals of metallic silver. A solution of common salt or brine, when electrically decomposed, will produce sodium and chlorine. The sodium appears at the leading-out electrode and readily unites with carbonic-acid gas, which is injected into the apparatus. The result of the combination is carbonate of soda, one of the most important products of the alkali industry.

Current, Alternating. A current flowing alternately in opposite directions. It is a succession of currents, each of short duration and of direction opposite to that of its predecessor. Abbreviation, A-C.

Current, Amperage. The volume of electricity passing through any circuit per second, the flow being uniform.

Current, Constant. An unvarying current. A constant-current system is one in which the current is uniformly maintained—for example, in electric light, power, and heat plants.

Current, Continuous. A current of one direction only, or the reverse of an alternating current.

Current, Direct. A current of unvarying direction, as distinguished from the alternating. Abbreviation, D-C.

Current Distribution, Uniform. A steady current; a current whose density in a conductor is always the same at all points.

Current, Induced. A current caused by electro-dynamic induction.

Current, Low Potential. A current of low pressure.

A term applied to low electro-motive force.

Current, Make-and-break. A current which is continually broken or interrupted and started again. The term is applied only where the interruptions occur in rapid succession, as in the action of an induction-coil or pole-changer.

The alternating current.

Current-meter. An apparatus for indicating the strength of a current, such as an ammeter.

Current, Oscillating. A current periodically alternating.

Current, Periodic. A current with periodically varying strength or direction. A current alternating periodically.

Current, Polarizing. A current which causes polarization.

Current-reverser. A switch or other contrivance for reversing the direction of a current in a conductor.

Current, Undulating. A current whose direction is constant but whose strength is continuously varying.

Currents, Eddy. Useless currents in an armature, in the pole pieces, and in the magnetic cores of dynamos and motors. They are created by the high speed of the armature in its rotation, or by other electric currents induced by the armature’s motion through magnetic fields.

Currents, Faradic. Induced currents. They take their name from Michael Faraday, the original investigator of the phenomena of electro-magnetic induction. The secondary or induced electro-magnetic currents and their accompanying phenomena.

A series of alternating electro-static discharges from influence machine, such as the Holtz and Wimshurst.

The simple and commonly understood Faradic currents are those produced in the medical battery, and used in medical therapeutics.

Currents, Foucault. A form of currents produced in revolving armature-cores; sometimes called eddy currents. They are useless.

Currents, Harmonic. Currents which alternate periodically, and vary harmonically. Currents which vibrate at certain pitches, as, for instance, the currents in wireless telegraphy. Two instruments must be tuned to the same pitch in order to be responsive. Thus an instrument sending out waves of 70,000 vibrations cannot be recorded by one tuned much below or above the same number.

Sound waves of sympathetic or harmonic vibrations.

Currents, Positive. (See Positive Currents.)

Cut-in. To electrically connect a piece of mechanism or a conductor with a circuit.

Cut-out. The reverse of the cut-in. To remove from a circuit any conducting device. The cut-out may be so arranged as to leave the circuit complete in some other way.

An appliance for removing a piece of apparatus from a circuit so that no more current shall pass through the former.

Cut-out, Automatic. A safety device for automatically cutting out a circuit to prevent accident or the burning-out of an apparatus, due to an overload of current. It is worked by an electro-magnet and spring. An overload of current causes a magnet of high resistance to draw an armature towards it, and this, in turn, releases the spring of the cut-out device. Sometimes a strip or wire of fusible metal is employed which is in circuit with a switch. The excess of current fuses the metal, and the broken circuit releases a spring-jack, which, in turn, breaks the circuit.

Cut-out, Safety. A block of non-conducting material, such as marble, slate, or porcelain, carrying a safety-fuse or plugs. In these is enclosed a piece of fusible wire, which burns out or melts and breaks the circuit before the apparatus is damaged.

Cut-out, Wedge. A cut-out operated by a wedge, such as a spring-jack or the plugs at the end of the flexible wires on the switch-boards of telephone exchanges.

D

Damper. A frame of copper on which the wire in a galvanometer is sometimes coiled. It acts to check the needle oscillations.

A brass or copper sheathing or tube placed between the primary and secondary coils of an induction-coil to cut off induction and diminish the current and potential of the secondary circuit. When the tube is drawn out gradually the induction increases. It is commonly used in medical coils to adjust their strength of action.

D-C. An abbreviation for direct current.

Dead Earth. A fault in telegraph and telephone lines which consists in the ground-wire being improperly grounded, or not fully connected with the earth.

Dead Turns. A term applied to the ten to twenty per cent. of the convolutions or turns of wire on an armature which are considered to be dead. There are supposed to be about eighty per cent. of the turns on an armature that are active in magnetizing the core; the balance are outside the magnetic field and are termed dead, although they are necessary to the production of electro-motive force.

Dead Wire. A wire in the electric circuit through which no current is passing.

A disused or abandoned electric conductor, such as a telegraph wire, or a wire which may be in circuit, but through which at the time of speaking no electrical action is taking place.

Death, Electrical. Death resulting from an electric current passing through the animal body—electrocution; accidental death by electric shock; premeditated death through bringing the body in direct contact with conductors carrying high electro-motive force. High electro-motive force is essential, and the alternating current is most fatal.

Decomposition, Electrolytic. The decomposition or separation of a compound liquid into its constituents by electrolysis. The liquid must be a conductor or electrolyte, and the decomposition is carried on by means of electricity.

The conversion of two or more chemicals into a new compound or substance.

Deflection. In magnetism, the movement of the needle out of the plane. It is due to disturbance, or to the needle’s attraction towards a mass of iron or steel or another magnet.

Demagnetization. The removal of magnetism from a paramagnetic substance. The process is principally in use for watches which have become magnetized by exposure to the magnetic field surrounding dynamos or motors.

Density, Electric. The relative quantity of electricity, as a charge, upon a unit area of surface. It may be positive or negative.

Surface density, as the charge of a Leyden-jar.

Depolarization. A term applied to the removal of permanent magnetism, such as that from a horseshoe magnet, a watch, or a bar-magnet. Heat is the common depolarizer, but counter electro-magnetic forces are employed also in the various forms of apparatus known as demagnetizers.

Deposit, Electrolytic. The metal or other substances precipitated by the action of a battery or other current-generator, as in the plating processes.

Detector. A portable galvanometer, by means of which a current and its approximate strength can be detected and measured.

Diaphragm. In telephones and microphones, a disk of iron thrown into motion by sound-waves or by electric impulse. It is usually a thin plate of japanned iron, such as is used in the ferrotype photographic process for making tin-types.

Dielectric. Any substance through which electrostatic induction is allowed to occur, such as glass or rubber. It is a non-conductor for all electric currents.

Dielectric Resistance. The resistance a body offers to perforation or destruction by an electric discharge.

Dimmer. An adjustable choke or resistance coil used for regulating the intensity of electric incandescent lamps. It is employed extensively in theatres for raising or lowering the brilliancy of lights.

Dipping. The process of cleaning articles by dipping them in acids or caustic soda, preparatory to electro-plating.

Simple immersion, with or without current, to put a blush of metal on a cleaned surface.

Dipping-needle. A magnetic needle mounted on a horizontal bearing so that it will dip vertically when excited by a current passing horizontally about it. The ordinary compass-needle is mounted on a point, and swings freely to the right or left only.

Direct Current. (See Current, Direct.)

Discharge. The eruptive discharge from a Leyden-jar or accumulator of a volume of electricity stored within it.

The abstraction of a charge from a conductor by connecting it to the earth or to another conductor.

Discharge, Disruptive. The discharge of a static charge through a dielectric. It involves the mechanical perforation of the dielectric.

Disconnect. To break an electric circuit or open it so as to stop the flow of current; to remove a part of a circuit or a piece of apparatus from a circuit.

Distillation, Electric. The distilling of a liquid by the employment of electricity, which, by electrifying the liquid, assists the effects of heat. It is asserted that the process is accelerated by the electrification of the liquid or fluid, but it must be a conductor liquid or electrolyte. Oil, being a non-conductor, is not affected by any electric current, no matter what its specific gravity may be.

Distributing Centre. The centre of distribution in a system having branch circuits, such as the electric-light or telephone outlets from a main station.

Door-opener, Electric. A magnetic contrivance arranged in connection with a lock, by means of which the latch is released by pressing a distant push-button. This device is used in flats and apartment-houses for opening a door from any of the apartments in the house.

Double Filament Lamp. An incandescent lamp having two filaments, one with a high capacity, the other with a low one. The high capacity may be from sixteen to fifty candle-power, the other from one to five. A turn of the bulb in its socket, or the pulling of a string which operates a switch in the socket, cuts out the current from the long filament and sends it through the shorter and finer one, thus giving a weaker light. These “hy-lo” lamps are useful as night lamps in halls, bath-rooms, or in sick-rooms, where a low or weak light is required all night.

Double Pole-switch. A cut-out that is arranged to cut out the circuit of both the negative and positive leads at the same time.

Double-push. A contact-push having two contacts and arranged so that pressure upon it opens one contact and closes the other.

Double Throw-switch. A switch so arranged that it can be thrown into either one of two contacts; a throw-over switch.

Driving-pulley. The broad-faced or channelled pulley on an armature shaft by means of which the power from a motor may be transmitted mechanically.

Dry Battery. (See Battery, Dry.)

Duct. The space in an underground conduit for a single wire or cable.

Duplex Wire. An insulated conductor having two distinct wires twisted or laid together, but properly insulated from each other.

Dynamic Electricity. Electricity in motion or flowing, as distinguished from static or frictional electricity.

Electricity of relatively low potential or electro-motive force in large quantity or amperage.

Dynamo. An apparatus consisting of a core and field-magnets, properly wound with insulated wire, which, when put into operation by revolving the core or armature at high speed, develops electric current; a mechanical generator of electricity.

Dynamo, Motor. (See Motor-dynamo.)

E

Earth. The accidental grounding of a circuit is termed an “earth.”

Earth-plate. A plate buried in the ground to receive the ends of telegraph lines and other circuits, and so give a ground connection. Copper plates are often used, but in houses the ground is usually formed by attaching a wire to the gas or water pipes.

Earth Return. The grounding of a wire in a circuit at both ends gives the circuit an earth return. This method is commonly used in telegraph lines, both in the wire and wireless systems.

Eddy Currents. (See Currents, Eddy.)

Edison Distributing-box. A box used in the Edison “three-wire” system, from which the outlets pass to local circuits.

Edison Lalande Cell. A zinc-copper battery having a depolarizing coating of copper oxide on the copper element, the couple being immersed in an electrolyte composed of potash or caustic soda.

Ediswan. A term applied to the incandescent lamps invented by Edison and Swan and used extensively in Great Britain. Also applied to other apparatus designed by the two inventors.

Efficiency. The relation of work done to the electrical energy absorbed. The efficiency is not equal to the energy absorbed, because it always takes more power to generate a current than is given back in actual efficiency. This is due to mechanical friction and to the resistance of the air in a mechanism such as a dynamo when revolving at high speed.

Efficiency, Electrical. In a generator it is the total electrical energy produced, both that wasted and that actually used in driving machinery or apparatus.

Efflorescence. The dry salts on a jar or vessel containing liquid that collects above the water or evaporation line. This is due to creeping.

Elasticity. A property in some bodies and forces through which they recover their former figure, shape, or dimensions when the external pressure or stress is removed. Water has no elasticity. Air is very elastic; steam has a great volume of elasticity; while electricity is undoubtedly the most elastic of all in its motion through air, water, and other conducting mediums.

Electric. Pertaining to electricity; anything connected with the use of electricity. It has been a much-abused word, and its meaning has been garbled by the impostor, the crook, and the “business thief” in foisting on the public wares in which there was no electrical property whatever. “Electric” toothbrushes, combs, corsets, belts, and the like may contain a few bits of magnetized steel, but they possess no active therapeutic value.

Electrical Engineer. The profession of electrical engineer calls for the highest knowledge of electricity, both theoretical and practical. It embraces the designing and installation of all kinds of electrical apparatus.

Electrician. One versed in the practices and science of electricity; a practical lineman or wireman.

Electricity. One of the hidden and mysterious powers of nature, which man has brought under control to serve his ends, and which manifests itself mainly through attraction and repulsion; the most powerful and yet the most docile force known to man, coming from nowhere and without form, weight, or color, invisible and inaudible; an energy which fills the universe and which is the active principle in heat, light, magnetism, chemical affinity, and mechanical motion.

Electricity, Atmospheric. The electric currents of the atmosphere, variable but never absent. They include lightning, frictional electricity, the Aurora Borealis, the electric waves used in wireless telegraphy, etc. Benjamin Franklin indicated the method of drawing electricity from the clouds. In June, 1752, he flew a kite, and by its moistened cord drew an electric current from the clouds so that sparks were visible on a brass key at the ground end of the cord. Later, when a fine wire was substituted for the cord, and a kite was flown in a thunder-storm, the electric spark was vivid. This experiment confirmed his hypothesis that lightning was identical with the disruptive discharges of electricity.

Electricity, Latent. The bound charge of static electricity.

Electricity, Negative. (See Negative Electricity.)

Electricity, Positive. (See Positive Electricity.)

Electricity, Voltaic. Electricity of low potential difference and large current intensity.

Electricity produced by a voltaic battery or dynamo as opposed to static electricity, which is frictional and practically uncontrollable for commercial purposes.

Electrification. The process of imparting an electric charge to a surface. The term is applied chiefly to electro-static phenomena.

Electrization. In electro-therapeutics, the subjection of the human system to electric treatment. An electric tonic imparted by electro-medical baths through the nervous system.

Electro-chemistry. That branch of science which treats of the relations between electric and chemical forces in their different reactions and compounds. It deals with electro-plating, electro-fusing, electrolysis, etc.

Electro-culture. The application of electricity to the cultivation of plants. The use of electricity has been found very beneficial in some forms of plant growth.

Electrocution. Capital punishment inflicted by electric current from a dynamo of high electro-motive force. The current used is from 1500 to 2000 volts, and it acts to break down the tissues of the body.

Electrode. The terminals of an open electric circuit.

The terminals between which an electric arc is formed, as in the arc-light.

The terminals of the conductors of an electric circuit immersed in an electrolytic solution, such as the carbon and zinc of a battery.

Electrolier. A fixture for supporting electric lamps, similar to a chandelier for gas or candles. Combination electroliers conduct both gas and electricity.

Electrolysis. The separation of a chemical compound into its constituted parts by the action of an electric current.

Electrolyte. A body susceptible of decomposition by the electric current. It must be a fluid body and a conductor capable of diffusion as well as composite in its make-up. An elemental body such as pure water cannot be an electrolyte.

Electrolytic Decomposition. (See Decomposition, Electrolytic.)

Electrolytic Deposit. (See Deposit, Electrolytic.)

Electrolytic Resistance. (See Resistance, Electrolytic.)

Electro-magnetic Induction. (See Induction, Electro-Magnetic.)

Electro-magnetism. Magnetism created by electric current.

That branch of electrical science which treats of the magnetic relations of a field of force produced by a current.

Electro-medical Bath. A bath provided with connections and electrodes for causing a current of electricity to pass through the body of the patient.

Electrometer. An instrument used for measuring static electricity. Electrometers are different from galvanometers, since the latter depend on a current flowing through wires to create an action of the magnetic needles.

Electro-motive Force. Voltage. It may be compared to the pressure of water in hydraulic systems. The unit of electro-motive force is the volt.

Electro-motor. A term sometimes applied to a current-generator, such as a small dynamo or voltaic battery.

Electro-plating. (See Plating, Electro.)

Electropoion Fluid. An acid depolarizing solution for use in zinc-carbon couples, such as the “Grenet” and “Daniell” cells. The bi-chromate-of-potash and sulphuric-acid solution for battery charges is a good example.

Electroscope. An apparatus for indicating the presence of an electric charge and whether the charge is negative or positive.

Electrostatic Accumulator. Two conducting surfaces, separated by a dielectric and arranged for the opposite charging of the two surfaces. A faradic or static machine for accumulating frictional electricity is an example.

Electrostatics. That division of electric science which treats of the phenomena of the electric charge, or of electricity in repose, as contrasted with electro-dynamics or electricity in motion.

Electrotype. The reproduction of a form of type or engraving by the copper electro-plating process. The original is coated with plumbago and a wax impression taken of it. The face of the negative is made conductive with plumbago or tin dust, then suspended in a copper bath and connected with the current. A film of copper will be deposited on the face of the wax impression.

Element, Chemical. Original forms of matter that cannot be separated into simple constituents by any known process. There are about seventy in all, but as science advances the list is constantly being revised. New elements are discovered and known ones are being resolved into simpler forms.

Elements of Battery Cell. (See Battery Cell, Elements of.)

Emergency Switch. An auxiliary switch used as a controller on a car to reverse the action of the motor.

E-M-F. An abbreviation for electro-motive force, or voltage.

Equalizer. A term applied to a wire or bar in electro-magnetic mechanism for equalizing the pressure over a system.

Exciter. A generator used for exciting the field-magnets of a dynamo.

Extension Call-bell. A bell connected with a telephone call-bell, and located in another part of a building so as to give a distant summons.

External Circuit. (See Circuit, External.)

F

F. The sign commonly employed to designate Fahrenheit. Thus, 30° F. means 30 degrees Fahrenheit, or 30 degrees above zero.

False Magnetic Poles. (See Magnetic Poles, False.)

Faradic. Induced current produced from induction-coils and faradic machines.

A series of alternating electrostatic discharges, as from a Holtz influence machine.

Faradic Coil. (See Coil, Faradic.)

Faradic Currents. (See Currents, Faradic.)

Faradic Machine. An apparatus designed to produce faradic current.

Feed. To furnish an electric current, also spoken of in connection with the mechanism that moves the carbons in arc-lamps.

Feeders, or Feed Wires. The conductors which convey electric currents at different points, as in the trolley system. The current is carried along in large cables strung on poles or laid underground, and at proper distances lines are run in to feed the trolley wire.

Field. The space in the neighborhood of a dynamo or motor, or other generator of electric current, from which the apparatus takes its electricity, both electrostatic and magnetic.

Field-magnet. (See Magnet, Field.)

Field of Force. The space in the neighborhood of an attracting or repelling mass or system. There are two kinds of fields of force—the electro-magnetic and the static—from which the respective pieces of apparatus draw their store of electricity.

Filament. A long, thin piece of solid substance. It is generally as thin as a thread and flexible enough to be bent.

The hairlike element in an incandescent lamp which, when heated by a current, glows and radiates light.

Filaments, Paper. Filaments for incandescent lamps made of carbonized paper. They were the ones originally used in electric lamps, but have been superseded by other substances easier to handle and more durable.

Flow. The volume of a current or stream escaping through a conductor, such as a wire, rod or pipe.

Fluorescence. The property of converting ether waves of one length into waves of another length. The phenomenon is utilized in the production of Geissler tubes and X-rays.

Fluoroscope. An apparatus for making examinations by means of the X-rays.

Fluoroscopic Screen. A screen overspread with fluorescent material and employed for fluoroscopic examinations in connection with the X-rays.

Force. Any change in the condition of matter with respect to motion or rest. Force is measured by the acceleration or change of motion that it can impart to a body of a unit mass in a unit of time. For instance, ten pounds pressure of steam will be indicated on a gauge made for measuring steam. That pressure of steam, with the proper volume behind it, is capable of instantly producing a given part of a horse-power. In the same way ten volts of electro-motive force is capable of pushing a current so as to exert a certain fraction of horse-power.

Force, Electro-magnetic. The force of attraction or repulsion exerted by the electro-magnet. It is also known as electric force in the electro-magnetic system.

Foucault Currents. (See Currents, Foucault.)

Fractional Distillation. The process of evaporating liquids by heat, the most volatile being the first treated. When that has been evaporated and distilled the heat is raised and the next most volatile liquid is evaporated, and so on until all are evaporated, leaving as a residue the solids that were a part of the original mass of liquid.

Friction. The effect of rubbing, or the resistance which a moving body encounters when in contact with another body.

Frictional Electric Machine. An apparatus for the development or generation of high-tension frictional electricity.

Frictional Electricity. Electricity produced by the friction of dissimilar substances.

Full Load. A complete load. The greatest load a machine or secondary battery will carry permanently. The full capacity of a motor running at its registered speed for its horse-power.

Furnace, Electric. A furnace in which the heat is produced by the electric arc. It is the hottest furnace known to man, and temperatures as high as 7500° Fahrenheit have been developed in it.

Fuse, Electric. A fuse for igniting an explosive charge by electricity. It is made by bringing the terminals or ends of wires close together, so that they will spark when a current passes through them. Or a thin piece of highly resistant wire may be imbedded in an explosive and brought to white heat by current.

Fuse-block. An insulator having a safety-fuse made fast to it.

Fuse-box. A box containing a safety-fuse, generally of porcelain, enamelled iron, or some other non-conductor.

Fuse-links. Links composed of strips or plates of fusible metal serving the purpose of safety-fuses.

Fusing-current. A current of sufficient strength to cause the blowing or fusing of a metal.

G

Galvanic. Voltaic. Relating to current electricity or the electro-chemical relations of metals.

Galvanic Taste. A salty taste in the mouth resulting from the passage of a light current from a voltaic battery, the ends of the wires being held to either side of the tongue. This has been called tasting electricity, but it is really the decomposition of saliva on the surface of the tongue, due to electrolysis or the passage of a current through a liquid.

Galvanism. The science of voltaic, or current, electricity.

Galvanizing. Coating iron with a thin layer of zinc by immersing the object in the molten metal.

Galvano-faradic. In medical electricity the shocking-coil. The application of the voltaic current, induced by a secondary current (induction-coil), to any part of the body.

Galvanometer. An instrument for measuring current strength.

A magnetic needle influenced by the passage of a current through a wire or coil located near it.

Galvanometer, Tangent. A galvanometer provided with two magnetic needles differing in length, the shorter one serving to measure tangents, the longer being used for sine measurements of current strength.

Galvanoscope. An instrument, generally of the galvanometer type, used to ascertain whether a current is flowing or not.

Generator. An apparatus for maintaining an electric current, such as a dynamo, a faradic machine, a battery, etc.

German-silver. An alloy of copper, nickel, and zinc. Used chiefly in resistance-coils, either in the form of wire or in strips of the sheet-metal.

Gold-bath. A solution of gold used for depositing that metal in the electro-plating bath.

Graphite. A form of carbon. It occurs in nature as a mineral, and also is made artificially by the agency of electric heat.

Gravity Battery. (See Battery, Gravity.)

Grounded Circuit. (See Circuit, Grounded.)

Ground-plate. (See Plate, Ground.)

Ground-wire. The contact of a conductor, in an electric circuit, with the earth. It permits the escape of current if another ground-wire exists.

Guard Tube. A tube inserted in a wooden or brick partition to insulate wires that may pass through it. These tubes are made of porcelain, gutta-percha, compositions of a non-conducting nature, and fibre.

Gutta-percha. Caoutchouc treated with sulphur to harden it; sometimes called vulcanized rubber or vulcanite. It is a product obtained from tropical trees, and when properly treated it is a valuable insulator in electrical work, particularly in submarine cables, since it offers great resistance to the destructive agencies of the ocean’s depths.

H

Hand Generator. A magneto-generator driven by hand for the generation of light currents.

Harmonic Currents. (See Currents, Harmonic.)

Harmonic Receiver. A receiver containing a vibrating reed acted on by an electro-magnet. Such a reed answers only to impulses tuned to its pitch.

Heat. One of the force agents of nature. It is recognized in its effects through expansion, fusion, evaporation, and generation of energy.

Heat, Electric. Caused by a resisting medium, such as carbon or German-silver, when too much current is forced through it. The principle of the car-warmers, electric iron, electric chafing-dish, etc.

Helix. A coil of wire. Properly a coil of wire so wound as to follow the outlines of a screw without overlaying itself.

Horse-power, Electric. Meaning the same as in mechanics. Referred to when speaking of the working capacity of a motor or the power required to drive a dynamo.

Horse-power Hour. A unit or standard of electrical work theoretically equal to that accomplished by one horse during one hour.

Horseshoe Magnet. (See Magnet, Horseshoe.)

H-P. Abbreviation for horse-power.

Hydrometer. An instrument employed to determine the amount of moisture in the atmosphere.

An instrument for determining through flotation the density or specific gravity of liquids and fluids. It consists of a weighted glass bulb or hollow metallic cylinder with a long stem on which the Baumé scale is marked. Dropping it into a liquid it floats in a vertical position, and sinks to a level consistent with the gravity of the fluid.

Hydrometer, Baumé. An apparatus for testing the gravity of fluids. The zero point corresponds to the specific gravity of water for liquids heavier than water. A gauge, valuable in testing acids and other fluids used in electrical work.

I

Igniter. A mechanical hand apparatus, in which a battery, induction-coil, and vibrator are located, and whose spark, jumping across a gap at the end of a rod, ignites or lights a gas flame, blasting-powder, or dynamite.

I-H-P. An abbreviation for indicated horse-power.

Illuminating Power. Any source of light as compared with a standard light—as, for instance, the illuminating power of an electric light reckoned in candle-power.

Illumination. A light given from any source and projected on a surface, per unit of area, directly or by reflection. It is stated in terms—as, for instance, the candle-power of a lamp. When speaking of an incandescent lamp we say it illuminates equal to four candle-power or it gives a light equal to sixteen candle-power.

Immersion, Simple. Plating, without the aid of a battery, by simply immersing the metal in a solution of metallic salt.

Impulse. The motion produced by the sudden or momentary action of a force upon a body. An electro-magnetic impulse is the action produced by the electro-magnetic waves in magnetizing a mass of soft iron and attracting to it another mass of iron or steel.

An electro-motive impulse is one where the force rises so high as to produce an impulsive discharge such as that from a Leyden-jar.

Incandescence, Electric. The heating of a conductor to red or white heat by the passage of an electric current. For example, an incandescent lamp.

Incandescent Circuit. (See Circuit, Incandescent.)

Incandescent Lamp-filament. (See Filament.)

India-rubber. (See Caoutchouc and Gutta-percha.)

Indicator-card. The card used in galvanoscopes, volt and ampere meters, and other instruments. It is provided with a moving needle and is marked with a graduated scale.

Induced. Caused by induction, and not directly.

Induced Current. (See Current, Induced.)

Inductance. That capacity of a circuit which enables it to exercise induction and create lines of force.

Inductance is the ratio between the total induction through a circuit to the current producing it.

Induction, Back. A demagnetizing force produced in a dynamo armature when a lead is given to the brushes. When the brushes are so set the windings on the armature are virtually divided into two sets: one a direct magnetizing set, the other a cross-magnetizing set which exerts a demagnetizing action on the other set. The position of the brushes on a dynamo or motor is indicated by their location, and if changed back induction will be the result.

Induction-coil. (See Coil, Induction.)

Induction, Electro-magnetic. When negative and positive currents are brought towards each other against their material repulsive tendencies the result is work, or energy, and the consequent energy increases the intensity of both currents temporarily. The variations thus temporarily produced in the currents are examples of electro-magnetic induction. A current is surrounded by lines of force. The approach of two circuits—one negative, the other positive—involves a change in the lines of force about the secondary circuit. Lines of force and current are so intimately connected that a change in one compels a change in the other. Therefore, the induced current in the secondary may be attributed to the change in the field of force in which it lies. The inner and outer coils of wire about the soft iron wire composing an induction-coil are the best and simplest examples of electro-magnetic induction.

Induction, Magnetic. The magnetization of iron or other paramagnetic substances by a magnetic field. The magnetic influence of a bar excited under these conditions is shown by throwing iron filings upon it. They will adhere to both ends (that is at the negative and positive poles) but not at the middle.

Inductor. A mass of iron in a current generator which is moved past a magnet-pole to increase the number of lines of force issuing therefrom. It is generally laminated, and is used in inductor dynamos and motors of the alternating-current type.

Influence, Electric. Electric induction or influence which may be electro-static, current, or electro-magnetic.

Influence Machine. A static electric machine worked by induction, and used to build up charges of opposite nature on two separate prime-conductors.

Installation. The entire apparatus, building, and appurtenances of a technical or manufacturing plant or power-house. An electric-light installation would mean the machinery, street-lines, lamps, etc.

Insulating Joint. Used for the purpose of insulating a gas-pipe from an electric circuit.

Insulating Varnish. A varnish composed of insulating material, such as gums, shellac, or diluted rubber. Shellac dissolved in alcohol is perhaps the best. It is easy to make and dries quickly, making an insulating surface practical for almost every ordinary use.

Insulation. The dielectric or non-conducting materials which are used to prevent the leakage of electricity. The covering for magnet wires, and overhead conduits for power lines and electric lighting.

Insulation, Oil. Any non-combustible oil may be employed as an insulator to prevent electrical leakage in induction-coils, transformers, and the like. Its principal advantage lies in its being in liquid form, permitting of easy handling. Moreover, if pierced by a spark from a coil, it at once closes again without becoming ignited. A solid insulator, if pierced, is permanently injured.

Insulator. Any insulating substance or material to prevent the escape of current. The knobs of porcelain or glass to which wires are made fast.

Insulator, Porcelain. An insulator made of porcelain and used to support a wire.

Intensity. The intensity or strength of a current is its amperage. The strength of a magnetic field, its power to attract or magnetize.

Internal Circuit. (See Circuit, Internal.)

Internal Resistance. (See Resistance, Internal.)

Interrupter. A circuit-breaker. Any device which breaks or interrupts a circuit. It may be operated by hand or automatically.

The vibrator of an induction-coil.

The commutators of an armature.

Isolated Plant. The system of supplying electric energy by independent generating dynamos for each house, factory, or traction line.

Isolation, Electric. A term applied to “electric sunstroke.” Exposure to powerful arc-light produces effects resembling those of sunstroke.

J

Joint. The point where two or more electric conductors join.

Joint Resistance. The united resistance offered by a number of resistances connected in parallel.

Jumper. A short circuit-shunt employed temporarily around an apparatus, lamp, or motor to cut out the current.

Jump-spark. A disruptive spark excited between two conducting surfaces in distinction from a spark excited by a rubbing contact.

K

Kaolin. A form of earth or product of decomposed feldspar composed of silica and alumina. It is serviceable in insulating compounds.

Kathode. The terminal of an electric circuit whence an electrolyzing current passes from a solution. It is the terminal connected to the zinc pole of a battery or the article on which the electro-deposit is made.

Key. The arm of a telegraphic sounder by which the circuit is made and broken. A pivoted lever with a finger-piece which, when depressed, makes contact between a point and a stationary contact on the base.

Keyboard. A board, or table, on which keys or switches are mounted.

A switchboard.

Kilowatt. A compound unit; one thousand watts; an electric-current measure. Abbreviation, K-W.

Kilowatt Hour. The result in work equal to the expenditure or exertion of one kilowatt in one hour.

Kinetoscope. A photographic instrument invented by Edison for obtaining the effect of a panorama or moving objects by the display of pictures in rapid succession—in familiar parlance, “moving pictures.”

Knife Switch. A switch with a narrow and deep, movable blade, or bar of copper or brass, which resembles the blade of a knife. It is forced between two spring-clamps attached to one terminal so as to make perfect contact.

L

Laminated. Made up of thin plates, as an armature-core.

Laminated Core. (See Core, Laminated.)

Lamp-Arc. A lamp in which the light is produced by a voltaic arc. Carbon electrodes are used, and a special mechanism operates and regulates the space between the carbons so that a perfect arc may be maintained.

Lamp, Incandescent. A lamp in which the light is produced through heating a filament to whiteness by the electric current. It consists of a glass bulb from which the air is exhausted and sealed, after the filament is enclosed. The ends of the filament are attached to platinum wires, which in turn are made fast to the contact-plates at the head of the lamp, so as to connect with the current.

Lamp-socket. A receptacle for an incandescent lamp. It is generally made of brass and provided with a key-switch to turn the current on and off.

Latent Electricity. (See Electricity, Latent.)

Lead. (Not the metal.) An insulated conductor which leads to and from a source of power; an insulated conductor to and from a telegraph or telephone instrument; a circuit, a battery, or a station. Not a part of the line circuit.

That part of an electric light or power circuit which leads from the main to the lamps or motors.

Leading-in Wires. The wires which lead into a building from an aerial circuit.

The wires which lead in and out from a lamp, battery, or instrument.

Leak. An escape of electrical energy through leakage. This is more liable to occur in bare than in insulated wires. The escape of current from bare trolley wires is much greater than that from the insulated conductors, particularly in damp or rainy weather.

Leclanché Battery. (See Battery, Leclanché.)

Leyden-jar. A type of static condenser. Its usual form is a glass jar. Tin-foil is pasted about its inner and outer surfaces covering about half the wall. The balance of the glass is painted with shellac or insulating varnish. The mouth is closed with a cork stopper, and through its centre a brass rod is passed which, by a short chain, is connected with the interior coating of the jar. The top of the rod is provided with a brass knob or ball, and from this last the spark is drawn.

Lightning. The electro-static discharge of clouds floating in the atmosphere. It is the highest form of frictional electricity, uncontrollable and very dangerous, since the strength of a single flash may run into hundreds of thousands of volts.

Lightning-arrester. An apparatus for use with electric lines to carry off to earth any lightning discharges that such lines may pick up; or it may be a form of fuse which burns out before the current can do any harm to the electrical mechanism.

Line-insulator. An insulator serving to support an aerial line.

Lineman. A workman whose business is the practical part of electrical construction in lines and conducting circuits.

Link-fuse. A plate of fusible metal in the shape of a link. It is used as a safety-fuse in connection with copper terminals.

Liquefaction, Electric. The conversion of a solid into a liquid by the sole agency of electricity in its heat action upon the solid.

Liquid Resistance. (See Resistance, Liquid.)

Lithanode. A block of compressed lead binoxide, with platinum connections, for use in a storage battery.

Litharge. Yellow-lead. A chemical form of metallic lead.

Load. In a dynamo, the amperes of current delivered by it under given conditions of speed, etc.

Local Action. In a battery, the loss of current due to impurities in the zinc. The currents may circulate in exceedingly minute circles, but they waste zinc and chemicals and contribute nothing to the efficiency of the battery.

In a dynamo, the loss of energy through the formation of eddy currents in its core or armature, in the pole pieces, or in other conducting bodies.

Lodestone. The scientific name is magnetite. Some samples possess polarity and attract iron; these are called lodestones.

Loop. A portion of a circuit introduced in series into another circuit.

Low Frequency. A frequency (in current vibrations) of comparatively few alternations per second.

Low Potential Current. (See Current, Low Potential.)

Luminescence. The power or properties some bodies have of giving out light when their molecular mass is excited. For example, phosphorus and radium.

Luminous Heat. The radiation of heat by electric current, which at the same time produces light. For example, the filament in an incandescent lamp.

Luminous Jar. A Leyden-jar whose coatings are of lozenge-shaped pieces of tin-foil between which are very short spaces. When discharged, sparks appear all over the surface where the small plates of metal nearly join.

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.