Fig. 188. SIR WILLIAM THOMSON'SAMPERE-METER GALVANOMETER.275 STANDARD ELECTRICAL DICTIONARY.In the cut P is the base board, M is a glass covered case containing themagnetic needle, and sliding along the base board, being guided by thecentral groove, C, is the coil. Between the coil and the needle is thearched or bent controlling magnet. The long twisted connecting wires areseen on the right hand.Galvano-plastics.The deposition of metals by electrolysis, a disused term replacedby electro-deposition, electroplating, and electro-metallurgy.Galvano-puncture.An operation in medical electricity. (See Electro-puncture.)Galvanoscope.An instrument, generally of the galvanometer type, used for ascertainingwhether a current is flowing or not. Any galvanoscope, when calibrated,if susceptible thereof, becomes a galvanometer.Gas, Electrolytic.Gas produced by the decomposition, generally of water, by electrolysis.It may be hydrogen or oxygen, or a mixture of the two, according to howit is collected. (See Gases, Mixed.)Gases, Mixed.The mixture of approximately one volume of oxygen and two volumes ofhydrogen collected in the eudiometer of a gas voltameter or otherelectrolytic apparatus.Gassing.The evolution of gas from the plates of a storage battery in thecharging process, due to too high voltage in the circuit of the chargingdynamo.Gastroscope.An apparatus for illuminating by an incandescent lamp the interior ofthe stomach, and with prisms to refract the rays of light so that thepart can be seen. The stomach is inflated with air, if desirable, togive a better view. An incandescent platinum spiral in a water jackethas been employed for the illumination.Gassiot's Cascade.A goblet lined for half its interior surface with tinfoil. It is placedin the receiver of an air pump from the top of whose bell a conductordescends into it, not touching the foil. On producing a goodrarefaction, and discharging high tension electricity from between theconductor just mentioned and the metal of the machine, a luminous effectis produced, as if the electricity, pale blue in color, was overflowingthe goblet.Gauss.A name suggested for unit intensity of magnetic field. Sylvanus P.Thomson proposed for its value the intensity of a field of 1E8 C. G. S.electro-magnetic units. J. A. Fleming proposed the strength of fieldwhich would develop one volt potential difference in a wire 1E6centimeters long, moving through such field with a velocity of onecentimeter per second. This is one hundred times greater than Thomson'sstandard. Sir William Thomson suggested the intensity of field producedby a current of one ampere at a distance of one centimeterThe gauss is not used to any extent; practical calculations are based onelectro-magnetic lines of force.276 STANDARD ELECTRICAL DICTIONARY.Gauss' Principle.An electric circuit acts upon a magnetic pole in such a way as to makethe number of lines of force that pass through the circuit a maximum.Fig. 189. GAUSS' TANGENT POSITION.Gauss, Tangent Positions of.The "end on" and "broadside" methods of determining magnetizationinvolve positions which have been thus termed. (See Broadside Method andEnd on Method.)Gear, Magnetic Friction.Friction gear in which the component wheels are pressed against eachother by electromagnetic action. In the cut, repeated from Adherence,Electro-magnetic, the magnetizing coil makes the wheels, which are ofiron, press strongly together.Fig. 190. MAGNETIC FRICTION GEAR.277 STANDARD ELECTRICAL DICTIONARY.Geissler Tubes.Sealed tubes of glass containing highly rarefied gases, and providedwith platinum electrodes extending through the glass tightly sealed asthey pass through it, and often extending a short distance beyond itsinterior surface.On passing through them the static discharge luminous effects areproduced varying with the degree of exhaustion, the contents (gas), theglass itself, or solutions surrounding it. The two latter conditionsinvolve fluorescence phenomena often of a very beautiful description.The pressure of the gas is less than one-half of a millimeter ofmercury. If a complete vacuum is produced the discharge will not pass.If too high rarefaction is produced radiant matter phenomena (seeRadiant State) occur.Geissler tubes have been used for lighting purposes as in mines, or forilluminating the interior cavities of the body in surgical or medicaloperations.Generating Plate.The positive plate in a voltaic couple, or the plate which is dissolved;generally a plate of zinc.Synonyms--Positive Plate--Positive Element.Generator, Current.Any apparatus for maintaining an electric current. It may be as regardsthe form of energy it converts into electrical energy, mechanical, as amagneto or dynamo electric machine or generator; thermal, as athermo-electric battery; or chemical, as a voltaic battery; all of whichmay be consulted.Generator, Secondary.A secondary or storage battery. (See Battery, Secondary.)German Silver.An alloy of copper, 2 parts, nickel, 1 part, and zinc, 1 part. Owing toits high resistance and moderate cost and small variation in resistancewith change of temperature, it is much used for resistances. From Dr.Mathiessen's experiment the following constants are deduced in legalohms:Relative Resistance (Silver = 1), 13.92Specific Resistance at 0° C. (32F.), 20.93 microhms.Resistance of a wire,(a) 1 foot long, weighing 1 grain, 2.622 ohms.1 foot long, 1/1000 inch thick, 125.91 "1 meter long, weighing 1 gram, 1.830 "1 meter long, 1 millimeter thick, 0.2666 "Resistance of a 1 inch cube at 0°C. (32° F.), 8.240 microhms.Approximate percentage increase of resistance per 1° C. (1.8° F.) atabout 20° C. (68° F.), 0.044 per cent.Gilding, Electro-.The deposition of gold by an electric current, or electrolytically inthe electroplating bath.Gilding Metal.A special kind of brass, with a high percentage of copper, used to makeobjects which are to be gilded by electrolysis.278 STANDARD ELECTRICAL DICTIONARY.Gimbals.A suspension used for ships' compasses and sometimes for otherapparatus. It consists of a ring held by two journals, so as to bc freeto swing in one plane. The compass is swung upon this ring, being placedconcentrically therewith. Its journals are at right angles to those ofthe ring. This gives a universal joint by which the compass, weightedbelow its line of support, is always kept horizontal.Fig. 191. COMPASS SUSPENDED IN GIMBALS.Glass.A fused mixture of silicates of various oxides. It is of extremelyvaried composition and its electric constants vary greatly. Manydeterminations of its specific resistance have been made. For flintglass at 100° C. (212° F.) about (2.06E14) ohms --at 60° C (140° F.)(1.020E15) (Thomas Gray) is given, while another observer (Beetz) givesfor glass at ordinary temperatures an immeasurably high resistance. Itis therefore a non-conductor of very high order if dry. As a dielectricthe specific inductive capacity of different samples of flint glass isgiven as 6.57--6.85--7.4--10.1 (Hopkinson), thus exceeding all otherordinary dielectrics. The densest glass, other things being equal, hasthe highest specific inductive capacity.Gold.A metal, one of the elements; symbol Au. c .; atomic weight, 196.8;equivalent, 65.6; valency, 3; specific gravity 19.5.It is a conductor of electricity.Annealed. Hard drawn.Relative Resistance (Annealed Silver = 1), 1.369 1.393Specific Resistance, 2.058 2.094Resistance of a wire at 0° C. (32°F.)(a) 1 foot long, weighing 1 grain, 57.85 58.84 ohms(b) 1 foot long, 1/1000 inch thick, 12.38 12.60 "(c) 1 meter long, weighing 1 gram, .4035 .4104 "(d) 1 meter long, 1 millimeter thick, .02620 .02668 "Resistance of a 1 inch cube at 0° C.(32° F.) .8102 .8247Approximate increase in resistance per 0° C., (1.8° F)at about 20° C. (68° F.), 0.365 per cent.Electro-chemical equivalent (Hydrogen = .0105), .6888279 STANDARD ELECTRICAL DICTIONARY.Gold Bath.A solution of gold used for depositing the metal in the electroplatingprocess.A great number of formulae have been devised, of which a fewrepresentative ones are given here.COLD BATHS. HOT BATHS.Water, 10,000 10,000 10,000 10,000 5,000 3,000Potassium Cyanide, 200 -- 200 10 -- 50Gold, 100 15 100 10 10 10Potassium Ferrocyanide, -- 200 -- -- 150 --Potassium Carbonate, -- 150 -- -- 50 --Ammonium Chloride, -- 30 -- -- 20 --Aqua Ammoniae, -- -- 500 -- -- --Sodium Phosphate, -- -- -- 600 -- --Sodium Bisulphite, -- -- -- 100 -- --(Roseleur.)In the baths the gold is added in the form of neutral chloride, Auricchloride (Au Cl6).Gold Stripping Bath.A bath for removing gold from plated articles without dissolving thebase in order to save the precious metal. A bath of 10 parts ofpotassium cyanide and 100 parts of water may be used, the articles to bestripped being immersed therein as the anode of an active circuit. Ifthe gilding is on a silver or copper basis, or on an alloy of thesemetals the same solution attacks the base and dissolves it, which isobjectionable. For silver articles it is enough to heat to cherry redand throw into dilute sulphuric acid. The gold scales off in metallicspangles. For copper articles, a mixture of 10 volumes concentratedsulphuric acid, 1 volume nitric acid, and 2 volumes hydrochloric acidmay be used by immersion only, or with a battery. The sulphuric acid insuch large excess is supposed to protect the copper. For copper articlesconcentrated sulphuric acid alone with the battery may be used. Thisdoes not sensibly attack the copper if it is not allowed to becomediluted. Even the dampness of the air may act to dilute it.Graduator.Apparatus for enabling the same line to be used for telegraph signalsand telephoning.One type consists in coils with iron cores or simply electromagnets.These act to retard the current in reaching its full power and alsoprolong it. This gives a graduated effect to the signals, so that thetelephone diaphragm is not audibly affected by the impulses.The telephoning current is so slight and so rapid in its characteristicchanges that it is without effect upon the ordinary telegraph.280 STANDARD ELECTRICAL DICTIONARY.Gram.The unit of weight in the metric system; accepted as the unit ofmass in the absolute of C. G. S. system of units. It is theone-thousandth part of mass of a standard weight preserved under properconditions in Paris, and supposed to be the mass of a cubic decimeter ofdistilled water at the temperature of the maximum density of water. Thestandard is the kilogram; the temperature is 3.9º C. (39º F.). Thestandard kilogram is found to be not exactly the weight of a cubicdecimeter of water, the latter weighing 1.000013 kilogram.If therefore the defined gram on the water basis is taken as the unit itvaries very slightly from the accepted gram.1 gram is equal to 15.43234874 grains. (Prof. W. H. Miller.)Gram-atom.The number of grams of an element equal numerically to the atomicweight, as 16 grams of oxygen, 1 gram of hydrogen, 35.5 grams ofchlorine; all which might be expressed as gram-atoms of oxygen, hydrogenand chlorine respectively.The gram-atom approximately expresses the number of gram-caloriesrequired to heat one gram of the substance 1º C. (1.8º F.). This is invirtue of Dulong and Petit's discovery that the atomic weight of anelement multiplied by its specific heat gives approximately a constantfor all elements.[Transcriber's note: A gram-atom is the mass, in grams, of one mole ofatoms in a monatomic element. A mole consists of Avogadro's number ofatoms, approximately 6.02214E23.]Gram-molecule.The number of grams of a substance equal numerically to its molecularweight.Graphite.Carbon; one of three allotropic modifications of this element. It occursin nature as a mineral.It is used as a lubricant for machinery; for commutator brushes; formaking surfaces to be plated conductive, and for mixing with manganesebinoxide in Leclanché cells.Gravitation.A natural force which causes all masses of matter to attract each other.Its cause is unknown; it is often supposed to be due to the luminiferousether.[Transcriber's note: Einstein's explanation of gravity, GeneralRelativity and the curvature of space-time, came 23 years later, 1915.]281 STANDARD ELECTRICAL DICTIONARY.Gravity, Acceleration of.The velocity imparted to a body in one second by the action ofgravitation at any standard point upon the earth's surface in a vacuum.This will vary at different places, owing principally to the variationin centrifugal force due to the earth's rotation. For standard valuationit must be reduced to sea level. The following are examples of itsvariation:Equator, 978.1028 centimeters per secondParis, 980.94 "Greenwich 981.I7 "Edinburgh, 981.54 "Pole (N. or S.), 983.1084 (theoretical) "As round numbers for approximate calculations 981 centimeters or 32.2feet may be employed.[Transcriber's note: The acceleration of gravity at the equator is alsoreduced by the increased distance from the center of the earth(equatorial bulge). Increased altitude reduces gravity. Reduced airdensity at altitude reduces buoyancy and increases apparent weight.Local variations of rock density affects gravity.]Gravity, Control.Control by weight. In some ammeters and voltmeters gravity is thecontrolling force.Grid.A lead plate perforated or ridged for use in a storage battery as thesupporter of the active materials and in part as contributing theretofrom its own substance.Ground.The contact of a conductor of an electric circuit with the earth,permitting the escape of current if another ground exists.Ground-wire.A metaphorical term applied to the earth when used as a return circuit.Fig. 192. GROVE'S GAS BATTERY.Grove's Gas Battery.A voltaic battery depending for its action on the oxidation of hydrogeninstead of the oxidation of zinc. Its action is more particularlydescribed under Battery, Gas. In the cut B, B1 * * * are the terminalsof the positive or hydrogen electrodes, marked H, and A, Al * * * arethe terminals of the negative or oxygen electrodes marked O, while M, M1* * * is dilute sulphuric acid.282 STANDARD ELECTRICAL DICTIONARY.Guard Ring.An annular horizontal surface surrounding the balanced disc in theabsolute electrometer. (See Electrometer, Absolute.)Guard Tube.A metal tube surrounding a dry pile used with a quadrant electrometer,or other electrometers of that type. It prevents the capacity of thelower brass end of the pile (which brass end closes the glass tubecontaining the discs) from momentary change by approach of someconductor connected to the earth. There are other guard tubes also.Gun, Electro-magnetic.An electro-magnet with tubular core. If, when it is excited a piece ofan iron rod is pushed into the central aperture of the core and isreleased, the magnetic circle will try to complete itself by pushing therod out so that it can thus be discharged, as if from a popgun.Synonym--Electric Popgun.Fig. 193. "ELECTRIC POPGUN."Gutta Percha.The hardened milky juice of a tree, the Isonandra gutta, growing inMalacca and other parts of the Eastern Archipelago. It is much used asan insulator or constituent of insulators.Resistance after several minutes electrification per 1 centimeter cubeat 54º C. (75º F.), 4.50E14 ohms.The specific resistance varies--from 2.5E13 to 5.0E14 ohms. A usualspecification is 2.0E14 ohms. The influence of temperature on itsresistance is given in Clark & Bright's empirical formula, R = R0 at, inwhich R is the resistance at temperature tº C--Ro the resistance at 0º C(32º F), a is the coefficient .8944.The resistance increases with the time of passage of the current, thevariation being less the higher the temperature.283 STANDARD ELECTRICAL DICTIONARY.Time of Relative Resistance Relative ResistanceElectrification. at 0º C (32º F.) at 24º C (75º F.)1 minute 100 5.512 " 127.9 6.5 " 163.1 6.6610 " 190.9 6.9420 " 230.8 7.3830 " 250.6 7.4460 " 290.4 7.690 " 318.3 7.66In cable testing one minute is generally taken as the time ofelectrification.Pressure increases the resistance by the formula Rp=R (1+ .00327 P) inwhich Rp is the resistance at pressure p--R resistance at atmosphericpressure--p pressure in atmospheres. Thus in the ocean at a depth of4,000 meters (2.4855 miles), the resistance is more than doubled. Thelonger the pressure is applied, the greater is the resistance.The specific inductive capacity of gutta percha is 4.2.Good gutta percha should not break when struck with a hammer, shouldrecover its shape slowly, and it should support much more than 300 timesits own weight.Gyrostatic Action of Armatures.Owing to gyrostatic action a rotating armature resists any change ofdirection of its axis. On ships and in railway motors which have to turncurves this action occurs. A 148 lb. armature running at 1,300revolutions per minute may press with 30 lbs. on each journal as theship rolls through an angle of 20° in 16 seconds.
283 STANDARD ELECTRICAL DICTIONARY.H.(a) The symbol for the horizontal component of the earth'smagnetization.(b) The symbol for the intensity of a magnetizing force or field. Thesymbol H, as it is generally used, may mean either the number of dyneswhich act upon a unit pole, or the number of lines of force percentimeter.(c) The symbol for the unit of self-induction.Hair, Removal of, by Electrolysis.A method of depilation by destruction of individual hair follicles byelectrolysis.A fine platinum electrode is thrust into a hair follicle. It is thenegative electrode. The positive electrode is in contact with the bodyof the person under treatment; it is often a sponge electrode simplyheld in his hand. A current of two to four milliamperes from an E. M. F.of 15 to 20 volts, is passed. This destroys the follicle, the hair isremoved and never grows again. A gradual increase of current is advisedfor the face. As only one hair is removed at once, but a small numberare taken out at a sitting.284 STANDARD ELECTRICAL DICTIONARY.Haldat's Figures.With a pole of a strong bar magnet, used like a pencil, imaginaryfigures are drawn upon a hard steel plate, such as a saw-blade. Thepattern is gone over several times. By dusting iron filings on a sheetof paper laid over the steel plate, while horizontal, very complicatedmagnetic figures are produced.Hall's Experiment.A cross of thin metal, such as gold leaf, is secured upon a pane ofglass. To two opposite arms a battery is connected in circuit with them.To the other two arms a galvanometer is connected in circuit. If thecross is put into a field of force whose lines are perpendicularthereto, the galvanometer will disclose a constant current. The currentis pushed, as it were, into the galvanometer circuit. Other metals havebeen used with similar results. They must be thin or the experimentfails. If the arm receiving the battery current is horizontal, and if itflows from left to right, and if the lines of force go from downwardthrough the cross, the current in the galvanometer circuit will flowfrom the observer through the other arms of the cross, if the cross isof gold, silver, platinum or tin, and the reverse if of iron. Theexperiment has indicated a possible way of reaching the velocity ofelectricity in absolute measure.Hall Effect.The effect observed in Hall's experiment, q. v.Hall Effect, Real.A transverse electro-motive force in a conductor through which a currentis passing produced by a magnetic field.Hall Effect, Spurious.A spurious electro-motive force produced in a conductor, through which acurrent is passing by changes in conductivity of the conductor broughtabout by a magnetic field.Hanger Board.A board containing two terminals, a suspending hook, and a switch, sothat an arc lamp can be introduced into a circuit thereby, or can beremoved as desired.Harmonic Receiver.A receiver containing a vibrating reed, acted on by an electro-magnet.Such a reed answers only to impulses tuned to its own pitch. If such arereceived from the magnet it will vibrate. Impulses not in tune with itwill not affect it. (See Telegraph, Harmonic.)Head Bath, Electric.A fanciful name for an electro-medical treatment of the head. Thepatient is insulated by an insulating stool or otherwise. His person isconnected with one terminal of an influence machine. An insulatedmetallic circle, with points of metal projecting inward or downward, isplaced about the head. The circle is connected with the other pole ofthe machine. On working it a silent or brush discharge with airconvection streams occurs between the patient's head and the circle ofpoints.285 STANDARD ELECTRICAL DICTIONARY.Head-light, Electric.An electric head-light for locomotives has been experimented with. Itincludes the parabolic reflection of the regular light with an arc-lampin place of the oil lamp. An incandescent lamp may be used in the sameplace, but has no great advantage over oil as regards illuminatingpower.Heat.A form of kinetic energy, due to a confused oscillatory movement of themolecules of a body. Heat is not motion, as a heated body does notchange its place; it is not momentum, but it is the energy of motion. Ifthe quantity of molecular motion is doubled the momentum of themolecules is also doubled, but the molecular mechanical energy or heatis quadrupled.As a form of energy it is measured by thermal units. The calorie is themost important, and unfortunately the same term applies to two units,the gram-degree C. and the kilogram-degree C. (See Calorie.) Caloriesare determined by a calorimeter, q. v.Independent of quantity of heat a body may be hotter or colder.Thermometers are used to determine its temperature.Heat is transmitted by conduction, a body conducting it slowly for somedistance through its own substance. Bodies vary greatly in theirconductivity for heat. It is also transmitted by convection of gases orliquids, when the heated molecules traveling through the mass imparttheir heat to other parts. Finally it is transmitted by ether waves withprobably the speed of light. This mode of transmission and the phenomenaof it were attributed to radiant heat. As a scientific term this is nowdropped by many scientists. This practice very properly restricts theterm "heat" to kinetic molecular motion.The mechanical equivalent of heat is the number of units of work whichthe energy of one unit quantity of heat represents. (See Equivalents,Mechanical and Physical.)Heat, Atomic.The product of the specific heat of an element by its atomic weight. Theproduct is approximately the same for all the elements, and varies asdetermined between 5.39 and 6.87. The variations are by some attributedprincipally to imperfection of the work in determining them. The atomicheat represents the number of gram calories required to raise thetemperature of a gram atom (a number of grams equal numerically to theatomic weight) one degree centigrade.286 STANDARD ELECTRICAL DICTIONARY.Heat, Electric.This term has been given to the heat produced by the passage of acurrent of electricity through a conductor. It is really electricallyproduced heat, the above term being a misnomer.The rise of temperature produced in a cylindrical conductor by a currentdepends upon the diameter of the conductor and on the current. Thelength of the wire has only the indirect connection that the currentwill depend upon the resistance and consequently upon its length.The quantity of heat produced in a conductor by a current is ingram-degree C. units equal to the product of the current, by theelectro-motive force or potential difference maintained between the endsof the wire, by .24.The cube of the diameter of a wire for a given rise of temperatureproduced in such conductor by a current is equal approximately to theproduct of the square of the current, by the specific resistance (q. v.)of the material of the conductor, by .000391, the whole divided by thedesired temperature in centigrade units.Heat, Electrical Convection of.A term applied to the phenomena included under the Thomson effect, q.v., the unequal or differential heating effect produced by a current ofelectricity in conductors whose different parts are maintained atdifferent temperatures.Heater, Electric.An apparatus for converting electrical energy into thermal energy.An incandescent lamp represents the principle, and in the Edison meterhas been used as such to maintain the temperature of the solutions.Heaters for warming water and other purposes have been constructed,utilizing conductors heated by the passage of the current as a source ofheat. (See also Heating Magnet.)Heating Error.In voltmeters the error due to alteration of resistance of the coil byheating. If too strong a current is sent through the instrument, thecoils become heated and their resistance increased. They then do notpass as much current as they should for the potential difference towhich they may be exposed. Their readings then will be too low. One wayof avoiding the trouble is to have a key in circuit, and to pass only aninstantaneous or very brief current through the instrument and thus getthe reading before the coils have time to heat.The heating error does not exist for ammeters, as they are constructedto receive the entire current, and any heating "error" within theirrange is allowed for in the dividing of the scale.Heating Magnet.An electro-magnet designed to be heated by Foucault currents induced inits core by varying currents in the windings. It has been proposed as asource of artificial heat, a species of electric heating apparatus forwarming water, or other purposes.287 STANDARD ELECTRICAL DICTIONARY.Heat, Irreversible.The heat produced by an electric current in a conductor of identicalqualities and temperature throughout. Such heat is the same whatever thedirection of the current. The heating effect is irreversible because ofthe absence of the Thomson effect, q. v.) or Peltier effect, q. v.Heat, Mechanical Equivalent of.The mechanical energy corresponding to a given quantity of heat energy.Mechanical energy is generally represented by some unit of weight andheight, such as the foot-pound; and heat energy is represented by agiven weight of water heated a given amount, such as a pound-degreecentigrade. Joule's equivalent is usually accepted; it states that772.55 foot pounds of mechanical energy are equivalent to 1 pound-degreeF. (one pound avds. of water raised in temperature one degreeFahrenheit). Other equivalencies have also been deduced.Heat, Molecular.The product of a specific heat of the compound by its molecular weight.It is approximately equal to the sum of the atomic heats of itsconstituent elements.The molecular heat represents the number of gram calories required toraise the temperature of a gram-molecule (a number of grams equalnumerically to the molecular weight) one degree centigrade.The molecular heat is approximately equal for all substances.Heat, Specific.The capacity of a body for heat; a coefficient representing the relativequantity of heat required to raise the temperature of an identicalweight of a given body a defined and identical amount.The standard of comparison is water; its specific heat is taken asunity. The specific heats by weight of other substances are less thanunity. The specific heat varies with the temperature. Thus the specificheat of water is more strictly 1+.00015 tº C.Specific heat is greater when a substance is in the liquid than when itis in the solid state. Thus the specific heat of ice is 0.489; lessthan half that of water. It differs with the allotropic modifications ofbodies; the specific heat of graphite is .202; of diamond, .147.The product of the specific heat by the atomic weight of elements givesa figure approximately the same. A similar law applies in the case ofmolecules. (See Heat, Atomic-Heat, Molecular.)The true specific heat of a substance should be separated from the heatexpended in expanding a body against molecular and atomic forces, andagainst the atmospheric pressure. So far this separation has not beenpossible to introduce in any calculations.288 STANDARD ELECTRICAL DICTIONARY.Heat, Specific, of Electricity.A proposed term to account for the heat absorbed or given out inunhomogeneous conductors, by the Thomson effect, or Peltier effect (seeEffect, Thomson--Effect, Peltier.) If a current of electricity beassumed to exist, then under the action of these effects it may beregarded as absorbing or giving out so many coulombs of heat, and thusestablishing a basis for specific heat.Heat Units.The British unit of heat is the pound degree F--the quantity of heatrequired to raise the temperature of a pound of water from 32° to 33° F.The C. G. S. unit is the gram-degree C.; another metric unit is thekilogram-degree C. The latter is the calorie; the former is sometimescalled the small calorie or the joule; the latter is sometimes calledthe large calorie. The term joule is also applied to a quantity of heatequivalent to the energy of a watt-second or volt-coulomb. This is equalto .24l gram degree calorie.Hecto.A prefix to terms of measurement--meaning one hundred times, ashectometer, one hundred meters.Heliograph.An apparatus for reflecting flashes of light to a distant observer. Byusing the Morse telegraph code messages may thus be transmitted longdistances. When possible the sun's light is used.Helix.A coil of wire; properly a coil wound so as to follow the outlines of ascrew without overlaying itself.Fig. 194. LEFT-HANDED HELIX.Fig. 195. RIGHT-HANDED HELIX.Henry.The practical unit of electro-magnetic or magnetic inductance. It isequal to 1E9 C. G. S., or absolute units of inductance. As thedimensions of inductance are a length the henry is equal to 1E9centimeters, or approximately to one quadrant of the earth measured onthe meridian.Synonyms--Secohm--Quadrant--Quad.289 STANDARD ELECTRICAL DICTIONARY.Hermetically Sealed.Closed absolutely tight. Glass vessels, such as the bulbs ofincandescent lamps, are hermetically sealed often by melting the glasstogether over any opening into their interior.Heterostatic Method.A method of using the absolute or attracted disc electrometer. (SeeElectrometer Absolute.) The formula for its idiostatic use, q. v.,involves the determination of d, the distance between the suspended andfixed discs. As this is difficult to determine the suspended disc andguard ring may be kept at one potential and the lower fixed disc is thenconnected successively with the two points whose potential difference isto be determined. Their difference is determined by the differencebetween d and d', the two distances between the discs. This differenceis the distance through which the micrometer screw is moved. Theheterostatic formula is:V' - V = (d' - d)* squareRoot( 8*PI*F / S )in which V and V' are potentials of the two points; d' and d the twodistances between the discs necessary for equilibrium; S the area of thedisc and F the force of attraction in dynes. (See Idiostatic Method.)High Bars of Commutator.Commutator bars, which in the natural wear of the commutator, projectbeyond the others. The surface then requires turning down, as it shouldbe quite cylindrical.High Frequency.A term used as a noun or as an adjective to indicate in an alternatingcurrent, the production of a very great number of alternations per unitof time--usually expressed as alternations per second.Hissing.A term applied to a noise sometimes produced by a voltaic arc; probablydue to the same cause as frying, q. v.Hittorf's Solution.A solution used as a resistance. It is a solution of cadmium iodide inamylic alcohol. Ten per cent. of the salt is used. It is contained in atube with metallic cadmium electrodes. (See Resistance, Hittorf' s.)Fig. 196. HITTORF'S RESISTANCE TUBE.290 STANDARD ELECTRICAL DICTIONARY.Holders.(a) The adjustable clamps for holding the armature brushes of dynamosand motors.(b) The clamps for holding the carbons of arc lamps.(c) The clamps for holding safety fuses, q. v.(d) Holders for Jablochkoff candles and other electric candles. (SeeCandle Holders.)(e) A box or block of porcelain for holding safety fuses.Hood.A tin hood placed over an arc-lamp. Such hoods are often truncated conesin shape, with the small end upwards. They reflect a certain amount oflight besides protecting the lamp to some extent from rain.Horns.The extensions of the pole pieces of a dynamo or motor. (See FollowingHorns-Leading Horns.)Synonym--Pole Tips.Horse Power.A unit of rate of work or activity. There are two horse powers.The British horse power is equal to 33,000 pounds raised one foot perminute, or 550 foot pounds per second, or 1.0138 metric horse power.The metric horse power (French) is equal to 75 kilogram-meters, or 542foot pounds per second, or .986356 British horse power.H. P. is the abbreviation for horse power. (See Horse Power, Electric.)Horse Power, Actual.The rate of activity of a machine, as actually developed in conditionfor use. It is less than the indicated or total horse power, becausediminished by the hurtful resistances of friction, and other sources ofwaste. It is the horse power that can be used in practise, and which inthe case of a motor can be taken from the fly-wheel.Horse Power, Electric.The equivalent of a mechanical horse power in electric units, generallyin volt-amperes or watts; 745.943 watts are equivalent to the activityof one British horse power; 735.75 are equivalent to one metric horsepower. The number 746 is usually taken in practical calculations to givethe equivalency.[Transcriber's note: Contemporary values are: Mechanical (British)horsepower = 745.6999 Watts; Metric horsepower = 735.49875 Watts]Horse Power, Indicated.The horse power of an engine as indicated by its steam pressure, lengthof stroke, and piston area, and vacuum, without making any deduction forfriction or hurtful resistances. The steam pressure is in accurate workdeduced from indicator diagrams.Horse Power, Hour.A horse power exerted for one hour, or the equivalent thereof. As thehorse power is a unit of activity, the horse power hour is a unit ofwork or of energy. It is equal to 1,980,000 foot pounds.H. P.Abbreviation for "horse power."291 STANDARD ELECTRICAL DICTIONARY.Hughes' Electro-magnet.A horseshoe electro-magnet with polarized core. It is made by mountingtwo bobbins of insulated wire on the ends of a permanent horseshoemagnet. It was devised for use in Hughes' printing telegraph, where veryquick action is required. The contact lasts only .053 second, 185letters being transmitted per minute.Fig. 197 HUGHES' ELECTRO-MAGNET.Fig. 198. HUGHES' INDUCTION BALANCE.Hughes' Induction Balance.An apparatus for determining the presence of a concealed mass of metal.The apparatus is variously connected. The cut shows a representativeform; a and a' are two primary coils, each consisting of 100 meters (328feet) of No. 32 silk covered copper wire (0.009 inch diameter) wound ona boxwood spool ten inches in depth; b and b' are secondary coils. Allcoils are supposed to be alike. The primary coils are joined in serieswith a battery of three or four Daniell cells. A microphone m isincluded in the same circuit. The secondary coils are joined in serieswith a telephone and in opposition with each other. The clock is used toproduce a sound affecting the microphone. If all is exactly balancedthere will be no sound produced in the telephone. This balance isbrought about by slightly varying the distance of one of the secondariesfrom the primary, until there is no sound in the telephone. If now apiece of metal is placed within either of the coils, it disturbs thebalance and the telephone sounds.292 STANDARD ELECTRICAL DICTIONARY.To measure the forces acting a sonometer or audiometer is used. This isshown in the upper part of the cut. Two fixed coils, c and e are mountedat the ends of a graduated bar. A movable coil d is connected in thetelephone circuit; c and e by a switch can be connected with the batteryand microphone circuit, leaving out the induction balance coils. Theends of the coils c and e, facing each other are of the same polarity.If these coils, c and e, were equal in all respects, no sound would beproduced when d was midway between them. But they are so wound that thezero position for d is very near one of them, c.Assume that a balance has been obtained in the induction balance withthe coil d at zero. No sound is heard whether the switch is moved tothrow the current into one or the other circuit. A piece of metal placedin one of the balance coils will cause the production of a sound. Thecurrent is turned into the sonometer and d is moved until the samesound, as tested by rapid movements of the switch, is heard in bothcircuits. The displacement of d gives the value of the sound.A milligram of copper is enough to produce a loud sound. Two coins canbe balanced against each other, and by rubbing one of them, or bybreathing on one of them, the balance will be disturbed and a sound willbe produced.Prof. Hughes has also dispensed with the audiometer. He has used a stripof zinc tapering from a width of 4 mm. (.16 inch) at one end to a sharpedge or point at the other. The piece to be tested being in place in onecoil, the strip is moved across the face of the other until a balance isobtained.As possible uses the detection of counterfeit coins, the testing ofmetals for similarity of composition and the location of bullets in thebody have been suggested. Care has to be taken that no masses of metalinterfere. Thus in tests of the person of a wounded man, the presence ofan iron truss, or of metallic bed springs may invalidate allconclusions.The same principle is carried out in an apparatus in which the parts arearranged like the members of a Wheatstone bridge. One pair of coils isused, which react on each other as primary and secondary coils. One ofthe coils is in series with a telephone in the member of the bridgecorresponding to that containing the galvanometer of the Wheatstonebridge. The latter is more properly termed an induction bridge.Synonyms--Inductance Bridge--Inductance Balance--Induction Bridge.293 STANDARD ELECTRICAL DICTIONARY.Hydro-electric. adj.(a) A current produced by a voltaic couple or the couple itself issometimes thus characterized or designated as a "hydro-electric current"or a "hydro-electric couple." It distinguishes them fromthermo-electric.(b) Armstrong's steam boiler electric machine (see HydroelectricMachine) is also termed a hydro-electric machine.Hydro-electric Machine.An apparatus for generating high potential difference by the escape ofsteam through proper nozzles.It consists of a boiler mounted on four glass legs or otherwiseinsulated. An escape pipe terminates in a series of outlets so shaped asto impede the escape of the steam by forcing it out of the directcourse. These jets are lined with hard wood. They are enclosed in or ledthrough a box which is filled with cold water.Fig. 199. ARMSTRONG'S HYDRO-ELECTRIC MACHINE.This is to partly condense the steam so as to get it into the vesicularstate, which is found essential to its action. Dry steam produces noexcitation. If the boiler is fired and the steam is permitted to escapeunder the above conditions the vesicles presumably, or the "steam" isfound to be electrified. A collecting comb held against the jet becomescharged and charges any connected surface.294 STANDARD ELECTRICAL DICTIONARY.The boiler in the above case is negatively and the escaping "steam" ispositively charged. By changing the material of the linings of the jets,or by adding turpentine the sign of the electricity is reversed. If thewater contains acid or salts no electricity is produced. The regularhydro-electric machine is due to Sir William Armstrong.Faraday obtained similar results with moist air currents.Hydrogen.An element existing under all except the most extreme artificialconditions of pressure and cold as a gas. It is the lightest of knownsubstances. Atomic weight, 1; molecular weight, 2; equivalent, 1;valency, 1; specific gravity, .0691-.0695. (Dumas & Boussingault.)It is a dielectric of about the same resistance as air. Its specificinductive capacity at atmospheric pressure is:.9997 (Baltzman) .9998 (Ayrton)Electro-chemical equivalent, .0105 milligram.The above is usually taken as correct. Other values are as follows:.010521 (Kohllrausch) .010415 (Mascart)The electro-chemical equivalent of any element is obtained bymultiplying its equivalent by the electro-chemical equivalent ofhydrogen. The value .0105 has been used throughout this book.Hygrometer.An instrument for determining the moisture in the air. One form consistsof a pair of thermometers, one of which has its bulb wrapped in clothwhich is kept moist during the observation. The evaporation is more orless rapid according to the dryness or moisture of the air, and as thetemperature varies with this evaporation the relative readings of thetwo thermometers give the basis for calculating the hygrometric state ofthe air. Another form determines the temperature at which dew isdeposited on a silver surface, whence the calculations are made.Hysteresis, Magnetic.A phenomenon of magnetization of iron. It may be attributed to a sort ofinternal or molecular friction, causing energy to be absorbed when ironis magnetized. Whenever therefore the polarity or direction ofmagnetization of a mass of iron is rapidly changed a considerableexpenditure of energy is required. It is attributed to the work done inbringing the molecules into the position of polarity.295 STANDARD ELECTRICAL DICTIONARY.The electric energy lost by hysteresis may be reduced by vibrations orjarring imparted to the iron, thus virtually substituting mechanical forelectrical work.On account of hysteresis the induced magnetization of a piece of iron orsteel for fields of low intensity will depend on the manner in which thematerial has been already magnetized. Let the intensity of fieldincrease, the magnetization increasing also; then lower the intensity;the substance tends to and does retain some of its magnetism. Then onagain strengthening the field it will have something to build on, sothat when it attains its former intensity the magnetization will exceedits former value. For a moderate value of intensity of field themagnetization can have many values within certain limits.Synonym--Hysteresis--Hysteresis, Static--Magnetic Friction.Hysteresis, Viscous.The gradual increase or creeping up of magnetization when a magneticforce is applied with absolute steadiness to a piece of iron. It maylast for half an hour or more and amount to several per cent. of thetotal magnetization. It is a true magnetic lag.