None
(Sw al80 Local Action.) Activity, Definition of, 826 Adjustment of Coil of Tangent Galvan- ometer, 85 for Sensibility in Voltmeter iExamples 30, 81), 187. 188 for Greatest Sensibility in Wheatstone's Bridge, 28d A(\justment8 for Sensibility in Am- meters, 188, 187, 142, 160 Agglomerate Block ased in Cells, 452, 458, 455 Alloys, Resistances of, per Centi- metre Cube and per Inch Cube, 259 Resistances of, per Foot Grain and per Metre Gramme, 2C1 Temperature Coeffloients of Resistance of; 266, 867 '— Pei-centage Variation in Resist- ances of, per 1°C., 266 Alternating Current, Definition of, 328 Aluminium, Resistance of, per Centi- metre Cube and per Inch Cube, 269 — — Resistance of, per Foot Grain and per Metre Gramme, 2G1 Amalgamated Zinc, Advantage of Using, in Cell, 429, 480 Zinc, Theories as to Action of, 430 Amalgamating Zinc, Method of, 420 Ammeter, 127-161, 179, 181-183, 188- 190, 328, 330, 366, 369, 492 Ayrton and Matlier's Moving Coil, 148 — r Ayrton's, Moving Coil with Magnetic Control, 160 Ayrton and Perry's Magnifying Spring, 135. {See also Am- meter, Magnifying Spring.) Ayrton and Perry's Permanent Magnet, ISO. (See also Am- meter, Permanent Magnet.) Definition of, 127 Disconnecting from Circuit, Result of, 181, 188 Evershed, 142 Gravity Control, 188-144 Gravity Control, Adjustment for Sensibility in, 142 Gravity Control, Evershed, Latest Form, 142 Gravity Control, How Defiecting Force Produced in, 139 Gravity Control, Nalder, 141 Gravity ControL Schuckert, 139 How Connected with CircuitL 181 602 AMM PRACTICAL ELECTRICirY. ANG Ammeter, How to Use, as Voltmeter, 179, 181 ■ TT'tHif fj} TTsc VuHujttci j.s, 153 Mitj^mifjing Spritig, 135-iaiS Mrii^rnfvfQjf 8pnivg, AdJiMtmeat lorftensibSUtyiti, 137 Maj^nilfyin^ Elprltig, A a pertaining Dtrtctlon of CurrojitwJtli, l:i8 MagTiifylu^ Rp^ng, Conditioris Onveiiilrfg Eqnstll^ of Divl- afoM of Sf^aJo itit 138 IfA^Tiirytn;; R^rlmi:, Effect of SisIjijlibininiiB Mi^ifiiflts op, 138 MA^|^ifym|g^ Spring/ Pmpdrlifin- *\UY h^ivftim Cmmeut und AoL^ikr DeHectJon lii^ 1S7 MagJil^ing Bprltiff, Hail Re if, 187 Magnifying Spring, Relative Positions of Iron Tube and Coil in, 136 Moving Coil, 144-161 Moving Coil, Adjustment for Sensibility in, 160 Moving Coil, Ayrton and Matlier's, 148 Moving Coil, Effect of Weaken- ing Magnet in, 160 Moving Coil, How Used to Measnre Large Currents, 188 Moving Coil, Weston, 144-148 Moving Coil, Weston, Use of, as Voltmeter, 183 Moving Coil with Magnetic Control, 160 Moving CoU with Magnetic Con- trol, Effect of Weakening Stationary Magnet in, 151 Nalder, 141 Needle, Various forms of, 131, 134, 140, 141, 142 Part of Wattmeter, Acting as, 830 Permanent Magnet, 180-185 Permanent Magnet, Adjustment for Reversal of Current in, 134 for i^iisibitity iit, liU Pei-irmneut Magi^tt, Difeatiria of Current 8hrjft'ii witli, 134 Permanent Bfa£:ii(!t, Iinproirpcl FormAOf IH^, 1S3 Permanent Blaffuet, MHlic«i of Obttioing atmisbt Line Low vnUky 132 Permanent Magnet, Proportion- ality between Deflection and Cuirent in, 130 — — Permanent Magnet, Result of Weakening Magnet in, 150 Ammeter Pointer, Various Forms of, 181, 134, 186, 137, 140, 142, 147, 149, 150 Scales for Currents of About the Same Value, 129 Scales for Currents of Very Different Values, 129 Scales, Various Forms of, 129, 130, 183, 136, 137, 139, 144, 147 Schuckert, 139 Short-Circuiting. Result of, 181, 183 Use of, for Measuring B.M.P. of Battery and P.D. between Terminals, 866, 492 Weston, 144-148, 183 What it Measures, 182 and Vdltmeter, Measurement of Electric Power with, 828 and Voltmeter, Measurement of Variable E.M.F. of Generator with, 869 and Voltmeter, Measurement of Resistance with, 185, 232, 492 Ammeters, Comparison of Methods of Exerting Controlling Force in, 128 Early Forms of, 180-188 How Straight Line Law Obtain- able in. APP 603 Needle, and Current, Rela- tion between, 82, 83 Anode, Definition of, 24, 88 for Silver Voltameter, Descrip- tion ef, 24 Weights of Salts Set Free at, 27 Antimony, Resistance of, per Centi- metre Cube and per Inch Cube, 260 Resistance of, per Foot Grain and per Metre Gramme, 2<5l Resistance, Percentage Varia- tion of, per 1°C., 266 Apparatus, Electrical, Enclosing in Conducting Case, 197 for Testing Connection between E.M.F. of Battery, P.D. be- tween Terminals, Resistance, and Current, 866 for Proving E.M.F. of Cell Independent of Positions and Sizes of Plates, 863 for Experiments on Polarisation of Cell, 422 for Altering the Arrangements of a Group of Cells, 63^-642 — - for Proving No Blectrostatic Force Inside Closed Con- ductor, 196, 216 for Proving tliat No Electricity at Rest Inside a Conductor, 210, 216 for Sliowing that Conductor Carrying Current is Moved by Magnet, 8, 4 for Showing that Current De- composes Liquid, 4, 7 for Showing tliatCurrentDeflects Magnet, 8 for Showing that Current Heats Conductor, 6, 8 for Showing that Current Mag- netises Iron, 8, 6 for Showing Mutual Action of Two Wires Carrying Currents, 8, 6 for Measuring Current. (See Measuring Current.) for Determining Property of Current Best to Measure its Strength by, 11, 15, 16, 17, 18, 21 for Producing Current. (See Battery, Cell, and Current- Generator.) for Testing Electric Density, 224 for Comparing B.M.Fs., 608 for Converting Electric Energy into Non-Heat Bnergj\ 871 -— for Introducing Electric Energy into Cireuit, 858 Apparatus for Measuring Heat Equi- valent of Electric Bneivy, 820, 821 for Measuring Energy, 813-324, 884-848 Illnstrating Electric Transmis- sion of Eneivy, 855, 857 for Calibrating Galvanometer by Using Known Resistances, 521 for Calibrating Galvanometer by Sine Method, 120 for Calibrating Any Galvano- meter by Comparison with Taneent Galvanometer, 109 for Calibrating Galvanometer by Comparison with Voltameter, 46 for Mapping Out Lines of Force Due to Coils. 71, 76, 100, 665 for Mapping Out Lines of Force Due to Magnets, 72-75, 665 for Showing Action of Magnet on Magnetic Needle, 67, 68 for Measuring Distribution of Magnetism in Bar Magnet, 64,65 for Testing Strength of Magnetic Field, 79, 96, 107 for Neutralising Uniform Mag- netic Field, 78 for Testing Ohm's Law, 170 for Measuring P.D. BAT Apparatus Employed by B.A. Com- mittee for Determining Unit of Resistance, 672 for Testing Resistance of Branch Circoito in Parallel. 294 '— for Comparing and Measuring Resistances. {Sca Comparing Resistances, and Measuring Resistance.) for Testing Sine Law. 118-117 Testing Sign of Charge and Potential 219-222 for Testing Tansent Law, 92, 93 for Calibrating 5eflectional Volt* meter, 188-187 for Graduating a Voltmeter with Clark's Cell, 516 for Testing Voltmeter. 511 Arc, Difficulty of Detennining Back B.M.P. of, 872 — Meaning of Apparent Resistance of, 283 Measuring Apparent Resistance of, 283 Armature of Motor, Definition of, 842 of Thomson Joulemeter, 848 of Thomson Joulemeter, Cause of Tl-+-.+!,-,iTr,f, fit''. of 1.. ■ .- .; . ■ i-E-, DirnC' ti^'iiK. Ill mm-jit^ HI, au of Hiomson Joiilemettirj Hr>w Jl<>1 iiiii of, ij3 Impcifled, M6 of T. -^11 Jcto3fiiuet«r, Man- 11 u Jd Produced by, ii-JL^ of! 11 JfliUemctfT, Hotn- ti"U ct, PraportEoiml tD Vnt^rgj Supplied, 347 Arms of WUefitatohe's Bri^lge, A<1- jii';tiNRBt of. to Obtiiiii of Wijealiit'One's Bridgi?, Law C'oiLEicctiiig RealfitAnceE of, 243 of Wheatetone's Bridge, Prac- tical Limitation to Inequality of. 284 of Wheatetone's Bridge, Resist- ance of One in Terms of Re- sistences of the Othei-s, 245 Aron Supply Meter, 889-841 Supply Meter, Differential Gear- ing for, 840 Arrangement of Group of Cells, Method of Altering, 589 Arrangemente of Cells, 580 Atomic Weighte of Copper, Silver, and Zinc, 27 Axis, Magnetic, Definition of, 67 Aylmer-Leclanche Cell, 455 Ayrton and Mather's Moving Coil Ammeter, 148 Ayrten and Mather's Non-inductive Resistance Coil for Large Corrente, 282 —— and Mather's Universal Shunt, silt] Mailiii I- LiiiiveJ'S&l Shunt Box. 3fri-310 ftnri Mather' B Z^rd Eleetrflstatic Valtmtfterj 1^, 179 Ajrriori and Forry'a &old-]&af Bleotro- SM>pe, 192 — Bni Fiijry'a JoiilemeteTr Original Gaining Clock FOTm^ 334 ah-\ l^eTry*flMftffnif;i^In|j Spring J fl4 flu. I Perry'a Ifjtgiilfying ftfnng Ammeter. 135-338 AiA Peny^H Obmmoter, 233 iiiHl Ptrr>N Ferttianent Magnet Animfeter, Vurious Fofius of, lao, 132, 133 AyrtoB^ Movlna Coil Ammeter with Magnetic Control, UtQ B Back E.M.F. (See B.M.F., Back.) Balance, Wheatetone's. {See Bridge, Wheatstone's.) with MOieatetone's Bridge, Definition of, 246 Bar Magnet, Apparatus for Measuring Distribntion of Magnetism Maifiifitj Lines of Forcse withj 72, 73 Butteries^ Mercury Switch-board foj", ' Willi DL^ereiit ArmngementH nf Cells, E.M.Fa of, 537, &SS with DlirerS]it. Arrahj^eineiil-i itt Ce\Uy Reaiiilatices of, fi^^S Battery aii<l External HeslBtanco with Opposing B.M,P.^ DJutribu- ti(!n of Potential in, 973 ArjTingiiig, to Froduca MjLxlmani Curreutj M& — - CbtuniuHl Action in, and ?fmiiboT of CelU, 350 ' Cost of Frodueing Bocird of Tr&fle Unit with* 4a2 - — Cuirtiil Beat by, B64, 538 Dpf4cn[iti™ of, 35»> ^t9 Diatriliutlon tjf Fotentfal En, wljttii Standing Gumqit, 377 Electromotive Force of^ a,'j*J- m: E.M.F. of, ConditlODE Govern- ing, aei E.BLF. of, DeAnltlon of, Ml E.M^F. of| Mcaioremant of, 36& BAT INDEX. BRI 605 Battery, B.H.F. of, P.D. between Tenninals, Resistance, and Gorrent, 364, 880 Back E.M.F. of. Method of MeasuriDg, 871 Muirhead's Telegr^>b, 485 P.D. between Terminals of, when Maximum Power Given to External Oircait, 889, 548 Potential in. Diagrams Show- ing Distribution of, 874-881, 384 Power Developed by, and Num- ber of Cells, 860 Prices of Materials Consumed in, 485 Produces Constant P.D. round Entire Circuit, 861 Ratio of Power Developed by, to Current, 870 Resistance (^, Measuring when Not Very Small, 498 Resistance of, Measuring when Very Small, 492 Resistance of. Measuring with Ammeter and Voltmeter, 866, 492 Single, Used for Working Several Telegraph Wires, 527, 528 Symbolical Representation of, 287 When Necessary to Join all Cells of, in Series, 552 B.A. Unit, Aim in Choosing, 576 Unit, Definition of, 578 Unit, First Indication of Value being Too Small, 576 Unit, Rayleigh's Value of, in C.G.S. Vim, 580 — — Unit, Value of, in International and Leml Ohms, 174, 587 Units of Resistance and Cur- rent, Aim in Choice of, 576 Volt, Definition of, 676 Volt, Value of, in International and Legal Volts, 175 Benolt, Law Connecting Variation of Resistance of Metals with Temperature, 264 Mascart, and De Nerville, Ohm Determined by, 582 BerthelOt, Measurements of Heats of Combustion by, 478, 481 Bismuth, Relative Electric and Heat Conductivities of, 275 Resistance of, per Centimetre Cube and per Inch Cube,. OAR Bridge, Wheatstone's, Balance with, Definition of, 246 Wheatstone's, Desirability of Using Key with, 250 Wheatstone's, Devices for Ex- pediting Use of, 253 Wheatstone's, Galvanometer and Battery Interchangeable in, 245 Wheatstone's, Proofe of Law of, 243 Wheatstone's, Measuring Very Large and Very Small Re- sistances by, 284 Wheatstone's, Methods of Using, 245 Wheatstone's, Portable Forms of, 285 Wheatstone's, Practical Limi- tation to Inequality of Arms of, 277, 284 Wheatstone's, Practical Limit to Range of Resistances, Measured by, 277 Wheatstone's, Principle of, 242 Wheatstone's, Resistance of One Arm Expressed in Terms of the Other Resistances, 245 Wheatstone's, Obtaining Great- est Sensibiliirr of; 285 Wheatstone's, subdivision of Wire of, into Lengths having Equal Resistances, 515 Wheatstone's, Value of Coils for, 283 Wire, Material for, 247 Wire, Advantage of Using Long, 249 Bright, Sir Charles, Proposes Names Ohmad and Volt, 578, 576 British Association Committee for Determining Unit of Re- sistance, Method Used by, 572 Association Committee, Olim Determined by, 581 Brush Discharge Proves Existence of P.D., 161 Blushes of Elihu Thomson Joule- meter, 848 Bunsen's CelL (See Cell, Bnnsen's.) Burnley Dry Cell, 459. (See aleo Cell, B.O.C. Dry.) Calibrating Ammeter witii Silver Voltameter, 26, 596 ^— Galvanometer by Comparison with Tangent Galvanometer, 108 Calibrating Galvanometer by Com* parison with Voltameter, 46 Galvanometer by Bine Method, 119^124 Galvanometer with Pivoted Needle by Sine Method, 120 Galvanometer with Suspended Needle by Sine Method, 121, 123 Galvanometer by Using Known Resistances and Cell of Con- stant E.M.F., 521 Galvanometer by Using Known Resistances and Constant P.D., 287 Galvanometer by Using Known Resistances, Other Methods of, 521 Galvanometer, Relatively or Ab- solutely, 25, 46 Voltmeters, Methods of, 183-187 Wattmeter, 382 Zero Electrostatic Voltmeter, 180 Calibration, Absolute, of Galvano- meter, Definition of; 45 Curve of Galvanometer, 52 Curve of Galvanometer, Con- struction of Scale from, 58 Curve of Gold-leaf Electroscope, How to Straighten, 195 Curve of Tangent Galvanometer, 84 Joint Relative of Two Galvano- meters, 238 — Relative, of Galvanometer, Definition of, 45 Straight Line Law, How Ob- tainable in Ammeters and Galvanometers, 125, 182, 187, 147 CaUaud Cell, 482 Callendar, Experiments on Tempera- ture CoefBcient of Platinum, 265 Calorie, Definition of; 8ia Power Required to Generate One, per Second, 479 Calories, Current, Resistance) and Time, Relation between, 318, 824 Calorimeter. GEL 607 Carlxms for Bunsen's Cell, Mauufac- tnre of, 444 Carpentier's Proportional Galvano- meter, Principle of, 125 Case, Conducting, (See Conducting Case.) Catliode, Definition of, 24, 38 for Silver Voltameter, Descrip- tion of, 23, 26 Weights of Metals Deposited on, Caustic Potash Consumed in Edison- Lalande Cell per Board of Trade Unit Produced, Weight and Cost of, 465, 487 Potash Consumed In Edison- Lalande Cell per Hour per 1,000 Amperes, 484 Cell, Amalgamating Zinc Plate of, 430 Aylmer Leclanchd, 455 Bunsen's, 443 Bunsen's, Compared with Grove's Cell, 443 Bunsen's, B.M.P. of, 444 Burnley Dry, 459. (See (Hso Cell, E.O.C. Dry.) CaUaud, 482 Chemical Action in, B.M.P. Calculated from, 477-482 Chemical Actions in Different Types of, 418, 424, 427, 488, 439, 446, 450, 463, 478 Chromic Acid, 445-448 Chromic Acid, Weights and Cost of Materials Consumed in, Ser Board of Trade Unit Pro- uced, 487 Chromic Acid, Weights of Materials Consumed in, per Hour per 1,000 Amperes, 484 Clark's, 466-477, 516-521, 5«8, 689, 590, 694, 697-699 Clark's, Board of Trade Form of, 470 Clark's, Board of Trade Specifi- cation for, 467, 497 Clark's, Board of Trade Specifi- cation, Notes to, 470, 492 Clark's, Cooper's Modification of Eahle's H Form of, 474 Ckrk's, Definition of, 467, 697 Clark's, EflTect on B.M.P. of Sending too Large a Current, 477 Clark's, B.M.P. of, 467, 470, 474, 688, 689, 694 Clark's, B.M.F. of. Temperature Variation of, 475 Clark's, B.M.F. of. Temperature Variation of, Afiected by Method of Construction, 475 Cell, Clark's, How to Set up, 468, 598 Clark's, Glazebrook's Notes to Specification of. 470, 592 Clark's, Eahle's Modification of Rayleigh's H Form of, 472 Clark's, P.D. between Terminals of, 689, 594 Clark's, Potentiometer Method of Graduating Voltmeter with, 616-519 Clark's Potentiometer Method of Testing Accuracy of Volt- meter Scale with, 510 Clark's, Preparation of Materials for, 467, 597 Clark's, Rayleigh's H Form of, 466 Clark's, Relative advantages of Two Types of, 474 Clark's, Resistuice Advisable for Use with, 477, 511 Clark's, with Fixed Resistance as Standard of OuiTcnt, 619 Copper - Zinc-Dilute - Sulphuric • Acid. (See Simple Voltaic Element.) Daniell's, 423-436, 461, 478, 484, 486 Daniell's, Chemical Action in, 424, 427, 478 Daniell's, Chemical Energy Converted into Electric Bnergy in, per Second per Ampere, 478 Daniell s. Compared with Leclanch6 Cell, 461 Daniell's, Copper Deposited per Hour per Ampere, 424 Daniell's, Copper Sulphate Con- sumed per Hour per Ampere, 426 Daniell's Depolariser of, 423 Daniell's, B.M.P. of. Calculated from Chemical Action, 478 Daniell's, B.M.P. of. Method of Maintaining Constant. 427 Daniell's, B.M.F. of, Values of, 426. 478, 639 Daniell's, B.M.F., Variation of, with Density of Solutions and Temperature, 426 Daniell's, Forms of, 431. (See also Cell, Calhind, Gravity, Meidinger, Minotto.) Daniell's, Local Actions in, 429, 430 Daniell's, Precautions in Con- struction of, 426, 428, 430, 431 608 CBL PRACTICAL BLECTRICmr. GEL Cell, DanleU'i, Freeaations when Us* iQff.426.427,485 Daniell's, Prevention of Copper Sulphate Dilltising through PorouB Partition of, 430 — Daniell's, Prevention of Forma- tion of Cupric Oxide in, 430 — — Dauiell's, Resfatance Varies with Constancy and Portability, Daniell's, Resistance of, Varies with Temperature, 486 — - Daniell's, Resistances of Various Forms of. 435 Daniell's, Weight and Cost of Materials Consumed in, per Board of Trade Unit Pro- duced, 486 ^—Daniell's, Weights of Materials Consumed per Hour per 1,000 Amperes. 484 Daniell's, Zinc Consumed per Hour per Ampere, 424 Daniell's, Zinc Sulphate Formed per Hour per Ampere, 425 De la Rue Silver Chloride, Un- suitability of, for Practical Use, 477 DepoUuiser First Used in, 423 - — K.O.C. Dry, 469 RC.C. Dry, Compared with Hellesen CeU, 460 B.C.C. Dry, B.M.F. of, 460 Bdison-Lalande, 462-465 Bdison-Lalande, Chemical Ac- tion in, 463 Bdison-Lalande, Depolariser of, 462 Bdison-Lalande, B.M.F. of, 464 Bdison-Lalande, Resistance of, 464 Bdison-Lalande, Weights and Cost of Materials Consumed in, per Board of Trade Unit Produced, 465, 487 Bdison-Lalande, Weights of Materials Consumed per Hour per 1,000 Amperes, 484 with B.M.F. Constant Used with Known Resistance for Cali- brating Galvanometer, 521 B.M.F. of. Calculated from Chemical Action in, 477-482 B.M.F. of, Compared with B.M.F. of Standard Cell, 502-510 B.M.F. of. Determined, with Voltmeter, 862. 865 with B.M.F. Helping Current May Abstract Bneray from Circuit. 882 Cell, E.M.F. of, P.D. between Ter- minals, Resistance, and Cur- rent, 364, 880 B.M.F. of. When Bqual to Ter- minal P.D., 522 B.M.F. of Different Types of, 426, 440, 444, 446, 451, 458, 450, 460, 462, 464, 467 B.M.FS. of, Independent of Hlm^t^ and 5ii:c of Fktec'i wifli IJiucIt EJf.F- Ahstra.rf:* B nervy fr4>izL Qirouit, 371, i^'^ Gasflriej' Dry, 4&fl Giki^^nt^r Dry, C£>iiinierclal Im- practicability of, 458 Gasttrtei- Dj^^ E. JLF. of* 4m Grjuily Daniel I*. 431^i3a, i^ Gmvity DftnigU s, Frecautioua whou Uaing, 432, 4'iQ Gr-ne's, 4Sfl-442, 4S>, 4S4, 48S, oi^l, 55CJ-S52 Giovp'!*j Ckfamlcal Action iui Gravii's^ Com].iarud wHh Bun- scTi'4 Oil. 443 Giovu'g, DeHOlEHisur of, iSS^ 43^ Gn)vu*ai B,H:F. (>n 440 Gic^Vfl'Sj E.M.F. |>imiiiiiihf;a wiXh Via of, 411 froin Clidinicnl Action, 4fiO Qrcjvo'a, Formerly used la Telo- graphy, &27 Qrovu's, N\ itric Aciil UsH Uii par Hoar per Ainptfe. Cfili 609 Cell, Lalande-CbaperoD, 462 Lalande-Chaperon, Defects of, 463 Leclanch6, 449-466, 484, 48T Leclanch^, Weights and Cost of Materials Consumed in, per Board of Trade Unit Pro- duced. 487 Leclanche, Weights of Materials Consumed per Hour per 1,000 Amperes, 484 Leclanch^, when used, 451 Ijeclanchd Agglomerate, 452 Leclanch^ Agglomerate, Forma- tion of the Agglomerate, 452 Leclanch^-Aylmer, 456 Leclanch^-Barbier, 462-455 Leclanch^-Barbier, Advantages of, 454 Leclanch^-Barbier, Composition of Salt Used in, 454 Leclanch^, Chemical Action in, 450 Leclanch6, Compared with Daniell'H Cell. 451 Ledanchd, Depolariser of, 460 Leclanch6, Disadvantages of, 452 Lcdanch^, E.M.F. of, 451 Leclanch^, Modifications of, 452-456 Leclanch^, Precautions in Con- straction of, 451 Local Action, How Caused in, 429,480 Mari^-Davy Mercuric Sulphate, Unsuitability of, for Practi- cal Use, 477 Meidinger, 431 Minotto's, 438 Obach Dry, 460 Obach Dry, B.M.F. of. 462 P.D. between Terminals of, Constant, when Low Internal Besistance, 522 P.D. between Terminals of. Diagram Showing None, 884 Polarisation of. Definition of, 364 Positive Plate of, Definition of, 376 Positive Terminal of. Definition of, 376 — Potassium Bichfomate, 445-448, 48^487 - — Potassium Bichromate, Chemi- cal Action in, 445 ——Potassium Bichromate, E.M.F. of, 446 — Potassium Bichromate, Precau- tions when Using, 445, 447 Cell, Potassium Bichronuite. Weights and Cost of Materials Con- sumed in, per Board of Trade Unit Produced, 487 Potassium Bichromate, Weights of Materials Consumed per Hour per 1,000 Amperes, 484 Potassium Bichromate, When Used, 447 Potassium Bichromate, with Porous Pot, 446 Potassium Bichromate, without Porous Pot, 445 Potential in, Diagrams Showing Distribution of, 374-381, 884 Potential in, Uncertainty as to Method of Variation of, 874 Potentials of Terminals of. Relatively to Earth, 376 Rate at which Chemical Energy is Converted into Electric Energy in, 361. 380, 382, 383 Rate at which Electric Energy is Given to, or Taken Arom, Outside Circuit by, 316, 380, 382,883 Rate at which Electric Energy is Converted into Heat in, 870, 380-384 Resistance of. Choice of Method for Measuring, 498 Resistance of. Conditions Gov- erning, 484 Resistance ofl Measuring when Not Very Small, 493 Resistance of. Measuring when Very Small, 366, 492 Safety Limitation of Maximum Current for, 559 Secondary. ^Su Accumulator.) Short-circuiting, How to Avoid Possibility of, when Using Mercury Switch-board, 640 Smee's, 423, 482 Sinee's, Production of Back E.M.F. in, 482 Storage. (See Accumulator.) Zinc and Copper, Signs of Ter- minals and Plates of, 376 Cells Abstracting Energy flroro Out- side Circuit, Diagi-am Show- ing, 384, 385 Arrangements of, 536 Arrangement of Circuit Re- quiring Least Number of, to Give Fixed Power to External Portion, 656 Arranging Given Number of, for Maximum Current, 646 Carbou Plate of, 443, 445, 460, 452, 458, 460, 461 610 CBL PRACTICAL ELBCTRICITT. CHB Celle, Oommerdal Yalae of Waste Prodacte of, 4S8, 400 •-— Conditions for Commercial Use of; for Electric Lighting, 491 Copper Oxide Plate o^ 463, 468 Copper PUte of, 419, 422, 481, 488,485 —— >Coft of Prodadng Board of Trade Unit with, 482, 488 — — Coupling with Mercnry Switch- board, Methods of, 541 Diftribation of Potential in, 874-880 Dry, 457-462 Dry, Advantages of, 457, 458 Dry, Early Attempts at Con- stmction of, 457 and Dynamo, Comparative Cost of Prodncing Electric Energy with, 482-491 E.M .Fs. of. Comparing, 602-510 Joined in Parallel, Series, and Parallel Series. 586-587 Joined in Parallel, E.M.F. of Battery Formed of, 588 Joined in Series, Curve Connect- ing Number of, and Current, 546 Joined in Series, E.M.F. of Battery Formed of, 587 Leclancl)^, Leclanch^-Barbier, and Aylmer-Leclanch^, Com- pafison between, 456 Local Action in. Method of Preventing, 429 — Minimum Number of, for De- livering Given Power, 553- 557 Minimum Number of, to Pro- duce Given Current and P.D,, 549 Negative Plate of, 419, 428, 481, 438, 435, 438, 443, 445, 450, 452, 453, 455, 460, 461, 462 Number of, in Series and Rate — - PltitinuT't Pltitt^ I'f, 4iL^ 13.^, 4^2 Folarisiistj Ituplflly, Meojiartiig KesLsCkijCti of, 4^ Pqiiitfve or Zinc Plata of^ 41 ^j 42^, 4S1, 43S, 43:^, -taS, Utt, 4[M, 454, r>5j 4ii8| 4&P, 4tt0, ii'.l, 402, 463 Potwtitial L[>at in, Grapliioil Ifeprvaentntioti of, S7i> Piiii-^ itt ^Aat^nuls Ci}u>iuuied in, 485 Resistances of, Methods of Measuring, 492-500 — in Series, Diagram Showing Dis- tribution of Potential in, 876 Cells, Single Fluid, 418, 445, 450, 462 for Telegraphy, 527 Two Fluid, 423, 433, 438, 443, 445,466 Use of, for Electric Lighting, 48fr-491 Waste of Energy in, 489, 491 C.G.S. Units Adopted for Electrical Measurements, 479, 576, 578, 583, 587, 593 Units, Value of Ampere, Ohm, and Volt in, 479, 678, 676« 578, 679, 683, 687, 593 Chaive, Distribution of, 224 Electric, Meaning of, 208 of Body, Variation of Potential with, 208, 209 Sign of, 214-231 Charged Body, Introduction of, into ' Conductor, 218 Chemical Action in Cell, Calculation of E.M.F. COI 611 Chromic Acid Cell. (See Cell, Potassium Bichromate.) Acid. {See Chromium Trioxide.) Cliromium Trioxide Coiwamed in Cell per Board of Trade Unit Pro- daced, Weight and Cost of, 48T Trioxide, Consumed in Cell per Hour per 1,000 Amperes, 484 Trioxide, Preparation of, 445, 447.448 Trioxide, Use of, as Depolariser in Cell, 445 Circuit) Abstraction of Energy from, by Generators, 871, 881 Arrangement of, Requiring T^ieast Number of Cells to giye Fixed Power to External Portion, 656 Back B.M.F. in, 870 Complete Electric, Description of, 852 Distribution of Potential in, 876 Distribution of Potential in, with B.M.F. Opposing, 878 Electric, Analogies with, 854, Electric, Mechanical Model Illustrating, 855-857 - — External, Arrangement of Bat* tery to Give Maximum Cur- rent and Power to, 545 External, Arrangement of Part of, to Receive Maximum Power, 893 External, Conditions Governing Variation of Potential along, 874, 875 External, E.M.F. of, to Receive Maximum Power ttom Given Current Generator. 898 External, Rate at which Energy Given to, or Taken firom, by Generator, 858. 871, 880-388 •"— External, Receiving Maximum Power from Given Generator, 885-308 External, with Opposing E.M.F., Distribution of Potential in, 878 External, Variation of Received Power from Maximum, 897 Introducing Electric Energy into, 858 Maintaining P.D. between Ends of, Con5itantt 287 Part of, in which Potential Diminishes in Dhrection of Current, 852 Part of, in which Potential Increases in Direction of Current, 353 Circuit, Power Absorbed in. Exterior to Generator, 870 Raising Potential of Electricity in,.358 Rate of Introduction of Electric Energy into, 858 — — Rate of Production of Heat in, 818-827 Single, Definition of, 877 Single, Uniformity of Current in,377 Circuits, Parallel. Independence of Currents in, 525 Clark's Cell. (See Cell, Clark's.) Clarky Latimer, Proposes Names Ohmad and Volt, 578, 576 Clock Joulemeter. CON Coils for Differential Galvanometer, Construction of, 240 —-for Differential Galvanometer, Equality of Magnetic Effects and Equality ol Besistance, 240 of Motor, 843 of Ohmmeter, 288 of One B.A. Unit of Resistance, Verification of, 674 for PortableWheatstone's Bridge, Values of, 287 of Proportional Galvanometer, 126 for Resistance Boxes, Values of, 288 of Shunt Box, 205, 297 of Thomson Joulemeter, 841-345 Resistance, Description of, 46 Resistance, Earliest Form, 569 Resistance, Kind and Gauge of Wire Employed in, 281, 282 Resistance, Magnetic Action in, 281 Resistance, Mode of Winding, Resistance, Spedflc Resistance and Temperature Variation of Materials of, 271 Resistance, Variation and Meas- urement of Temperature of, 280,281 Resistance, When Used, 278 Combined Resistance, Definition of, 291 Combustion, Measurement of Heats of, 478, 481 Commercial Efficiency of Generator, and of Motor, Definition of, 406 Efficiency of Transmission, De- finition of, 409 Forms of Wattmeters, 831 Commutator, Description of, 842 of Bliliu Thomson Joulemeter, 843,848 Comparing B.M.Fs. of Cells, 602-510 (See cUso Measuring E.M.F.) P.Ds. by Current Method, 176 (See cUso Measuring P.D.) Quantities of Electricity, 211 Resistances in Parallel by Differential Galvanometer, 238 Resistances in Parallel by Wheat- stone's Bridge, 241-258 Resistances in Series, 177, 184, 186 Resistances by Simple Subetitu- tion,286 Comparing Resistances. (See aho Measuring Resistance.) Comparison Coils of Wheatslone'a Bridge, 285, 287 Compass Needle, Conditions Govern- ing Rate of Vibration of, 79 Needle, Connection between De- flection of, and Direction of Current Round, 84 Needle, Mapping Out Lines of Force with, 76 Needle, Measuring Strength of Magnetic Field with, 79 Needle, Method of Increasing Moment of Inertia of, 79 Needle Showing Direction of Current through Magnifying Spring Ammeter, 188 Conducting Case, Advantage of En- closing Electrical Apparatus in, 197, 200 Case Surrounding Chai^ Body, Conditions Goyeming Screen- ing Action of, 228 Case, Testing Power of, as Electrostatic Screen, 198 Cases Necessary for Electro- static Voltmeters, 198 Cases, Various Forms of, 197-200 'System, Condition for Uniform Potential at All Parts, 166 Transparent Varnish, Composi- tion of, 200 • TntTT^p^Fi^ut Vamtsbj Ufie of, ItW, n% IQ9 Ctt]n}\iiit\on, Dti^Ihltiofi of, ^IS. COP 613 Conductor with Current Passing and Magnet. Force Exerted Be- tween, 8, 129 Effect of Changing Shape of, on Current, 173 Electrified by Conduction or In- duction, 218 Equivalent, and Branch Circuits, Conductivities of, 292, 293 No Electricity at Best Inside, 209 P.D. Maintained Constant be- tween two Points of, 158. 510 Position of, for Magnet to Exert Greatest Force on, 129 Potential of, Definition of, 200 Potential of, and Quantity of Electricity on, 206-231 Quantity of Electricity on. Definition of, 212 Ratio of P.D.to Current through. Constant, 170 Reduced Length of, Definition of, 568 Resistance of. Varies with Cross Section, 254. 257 - — Resistance of, Varies with Length, 253-256 Resistance of. Varies with Material, 254, 257-262 Resistance of, Varies with Tem- perature, 233, 254, 262-271 Warmed by Current, 5, 8, 318 Conductors in Parallel, Combined Resistance of, 292 Parallel, Resistances of, and Currents Passing, 238 Parallel, Ratio of Currents in, to Current in Main, 295 P.D. between, Definition of, 161 P.D. between, How Shown, 161 P.D. between, When One Sur- rounds the Other, 218 Specific Resistances and Tem- perature Coefficients of, 2G7 With Negative Temperature Change of Resistance, 2<J7, 269, 271, 312 With No Temperature Change of Resistance, 269 With Small Temperature Change of Resistance, 266-271 Constant and Uniform, Difference between. Note. 158 B.M.F., 522 for Tangent Galvanometer, a.d. 1891-1900, 104 P.D., 522 Construction of Galvanometer Scale Giving Relative Current Strengths, 68 Construction of Galvanometers with Angulitr Deflection Directly Proportional to Current, 124 of Ping Resistance Boxes, 277 of Shunt Boxes, 295, 304 of Sulphuric Acid Voltameter, 38 of Tangent Galvanometer Scale, 88 of Wheatstone's Bridee, 246 Controlling Field on Oiuvanometer Needle having Very Small Deflections, 126 Field on Galvanometer Needle, When Uniform, 80, 81, 126 Force, Calibrating Sine Galvano- meter, by Altering Direction of, 123 and Deflecting Forces on Gal- vanometer Needle, 70, 81, 102, 111 Force in Ammeters, Comparison of Methods of Exerting. 128 Force of Earth on Tangent Gal- vanometer, Alteration of, 103 Force, Total, on Tangent Gal- vanometd*, Determination of, 104 Cooper's Modification of Kah1e*s H Form of Clark's Cell, 474 Copper and Silver, Comparative Rates of Electric Deposition of, 28 Atomic Weight of, 27 Deposited m Voltameter, per Second, per Ampere, 27 Electrochemical Equivalent of. Variation of, with Area and Temperature, 28 Percentage Conductivity o^ Definition of, 274 Phite of Cells, 419, 421, 481, 433. 485. (Sefi also Plate, Copper.) Relative Electric and Heat Conductivities of, 276 Resistance of, per Centimetre Cube and per Inch Cube, 259 Resistance of, per Foot Grain and per Metre Gramme, 261 Resistance of, and Temperature, Equations Connecting, 265 Resistance, Percentage Varia- tion of, per 1°C., 266 Resistance, Variation of, with Density, 258, NoU, 312 Temperature Coefficient of, 265, 266 Oxide Consumed in Edison- Lalande Cell per Board of Trade Unit Produced, Weight and Cost oi; 465, 487 6U OOP PBAOTICAL BLECTRICITT. CUR Copper Oxide Contnmed in Edison- Lolande Cell per Hour per 1,000 Amperes. 484 Oxide Plate of Cell. 462, 468 Sulphate consumed in Daniell's Cell per Board of Trade Unit Produced, Weight and Cost of, 486 — - Sulphate Consumed in DanielPs Cell per Hour per 1,000 Amperes, 425, 484 Sulphate, DitTusion of, in Daniell's Cell, 430 Sulphate, Heat Absorbed in Decomposition of, 478 Voltameter, 10 Voltameter, When Used, 26 Coet and Weiffhts of Materials Con- sumea in Cells per Boanl of Trade Unit Produced, 486, 487 Comparative, of Using Cells and Dynamo, 482 of Producing Board of Tmde Unit. 488, 491 of Producing Board of Trade Unit, with Bfattery, Con- ditions Governing, 482 Coulomb, Definition of, 579 Coulombmeter, Definition of, 848 Crumpton Standard Resistance Used in Measuring Current, 520 Cupric Oxide, Preventing Formation of, in Daniell's Cell, 430 Current, Absolute Electromagnetic Unit of. Definition of, 575 Alternating, Definition of, 828 and Given Number of Cells in Series, Curve Connecting, 546 and P.D., Given, Minimum Number of Cells to Produce, 549 Best Cell to Produce Strong, for Short Time, 447 Board of Trade Standard of, 594, 595 Calories, Resistance, and Time, Relation between, 318, 324 Change in, and Diminution from Maximum of Power Given by, 897 Choice of Method for Measuring, 9-14 Decomposition of Liquid by, 4,10 Deflection of Magnet by, 8, 5, 84,69 Direction of, in Cells, 428, 424, 427, 438, 439, 445. 446, 450, 463 Direction of Flow, Definition of, 2, 81 Current, Diroetion of. How Deteiv mined, 84, 184 Direction of, and Magnetic Polarity, Connection be- tween, 86 Direction of, When Necessary to Know, 184 Density, Definition of, 483 Electric, Compared witli Cur- rent of Water, 2, 5, 13, 152, 813, 853, 354 Electric, What is Meant by, 2 of Gas, Measurement of Distri- bution of Pressure in, 158 Generator, Arrangement of, to give Maximum Power to Ex ternal Circuit, 395 Generator, Commercial Effic- iency of, 406 Generator, Electrical Efficiency of, 406 Generator with B.M.P. Helping May Abstract Energy, 881 '~— -Generator, E.M.F. of, and Loss of Power in Electiic Trans- mission, 410 Generator, E.M.F. of. Definition of, 869 Generator, External Circuit Re- ceiving Maximum Power from, 885-895 Generator, Finding Circuit Re- ceiving Maximum Power ' from, 391 Generator, Measuring E.M. F, of, 369 Generator of Fixed KM.F. Equals Current into E.M.F. of, 370 Generator with VarhibleE.M.P., 369 47eiw^rat<iT,Work doiiy byjl^'Tii^jO Hi'iit I'nJtUic&i by, fi, I*, SIS liicinjnse of, in, Main by Apply- in Dflttory, P.U. between Tcr^ jfdnalfl^ E,M,F. aud Ki^lsl- iiTic^j 3tJ4 kiiHiitifry, PrnpoitiotiAltoCIiciii- h'O.} AiitiQii, 35D Ill Cell ill Tifniifl {if FhT>., E.M.F., in Crrcmt^ V.U. Imlviirn Ter- Tjiiiialii^ and Power, S70 CUR INDEX, CUB 615 Correlit in Circuit, Uniform Strength of, 152, 877 in Daniell's Cell, Yarifttion of, with Temperatare, 430 in Galvanoroeter and Deflection of Needle, 45, 84, 112, 124, 127 in Galvanometer and Force Keeping Needle at Best, 70 in Tangent Galyanometer with Earth's Control, Formula Giving, 108 in Generator, Batio of, to Power Developed, 870 in Magnifying Spring Ammeter Ftvportional to Angular De- fleeUon, 187 — — in Simple voltaic Element, Cause of Diminution of, 421 — — in Voltameter, Direction of, 88 — : Magnetiaation of Iron by, 8, 5, 85 Kazimum, for CelL Safety Limitation of, 559 ^—Maximum, through Given Ex- ternal Besistanoe, Arrange- ment of Given Number of Cells to Produce, 545 Measured by Chemical Property, 14-28 Measuring, Board of Trade In- struments for, 588 Measuring with Ammeter, 127. (See also Ammeter.) Measuring with Clark's CeU and Known Besistance, 519 Measuring witli Copper Volta- meter, 10, 26 Measuring with Silver Volta- meter, 23-26, 695 Measuring with Voltmeter and Fixed Besistance, 189 Measuring, Instruments for. (5m Ammeter, Calorimeter, Electromagnet, Galvano- meter, Galvanoscope, Volta- meter.) Measuring Bate of Heat Pro- duced by, 819 Measuring, Standard Besistance Used in, 520 Measuring. {See also Measuring Current.) Method of Comparing P.Ds., 176 P.D. to Send, round Entire Circuit Constant for Given Battery, 861 Power, and P.D., Belation be- tween, 827 — • Primary, Direction of, in Expe- rimental Voltaic Element, 423 Cnrrent^ Production of, 156. (Set tito Battery, Cell, and Current- Generator.) Producticm of, between Two Conductors, 161 Properties of; 8 Property of, Best to Meaaon Strength by, 20 Proportional to Bate of Chemical Action, 22, 861 Batio of P.D. to. Constant for given Conductor, 170 Batio of P.D. to, for given Conductor, Experimentally Determined, 171 Beversing Direction of, without Altertag Value, 87 Secondary, Direction of, in Experimental Voltaic Ele- ment, 423 Strength, Definition of, 23 Unit of. {Set Ampere.) Unit of, Aim of B.A. Commit- tee in Choosing, 576 Uses of Different Properties of, 9 Variation of EflTect of Shunt on with Change of External Besistance, 299 Variation of Light of Glow Lamp with Change of, 490 Variation of, with Change of Back E.M.F., 372 of Water Compared with Electric Current, 2, 5, 13, 152, 313, 353.354 of Water, How Mahitained, 150 of Water and Loss of Head, 168-156 of Water, Work Done by, 813 Electric, Work Done by, 813 Voltmeter. {Set Voltmeter.) Currents, Eddy or Foucault, 147 in Aimature of Elihu Thomson Joulemeter, Directions of, 844 in Batteries with Different Ar- rangements of Cells, 537 in Elihu Thomson Joulemeter Proportional to Magnetic Fields Produced, 840 in Parallel Circuits, Independ- ence of, 625 in Paiallel Conductors, Batio of, to Current in Main, 295 in Shunt and Galvanometer, Batio between, 290 in Shunt and Galvanometer Batio of each to Whole Current, 290J Local, 429 616 CUR PRACTICAL ELECTRICITT. DI7 Ciirrento Fusing tbroiu;h Two Con- dactoni in Puailel, M essnre- ment of, 288 — — Through Two Conductors in Parallel Inyersely Propor- tional to Resistances, 238 Conra, Calibration. {See Calibration CnrveJ — Connecting Galvanometer De- flection and Corrent, 52 Connecting Power Received by External Circuit with its Resistance, 401, 402 —— > Connecting Rate of Flow of Water with Loss of Head, 168 How General Cliaracter of Re- sult Obtained Shown by, M ^— Recording Results of Exjieri- nient for Calibrating Gal- vanometer, 52 Showing Current Giving Maxi- mum Power to External Circuit, 887 Curves, Choice of Absdssse, Ordinates and Units for, 57 Connecting Variation of Resist- ance of Metals wiUi Temper- ature, 264. 265 Drawing, on Squared Paper, 51 How Drawing of, Corrects Re- sults of Experiments, 55 Results of Intermediate Untried Exiieriments Obtainable fh>m, 55 Showing Tests on Three Types of Leclanch^ Cell, 456 Cylinder, Zinc Plates of Cells in Form of, 481, 455, 461 Dftnieirs Cell. (See Cell, Daniell's.) Use of DeiKilnriser, 428 D* Arson val Galvanometer, Motiifica- tlons of, 144-151 Galvanometer, Principle of, 130 Dftvy's Work on Electrical Resistance of Metals, 568 Dead Beat, Meaning of, 134 — — Beatness of Various Forms of Ammeters, 184, 147, 149 Decomposition of Liquid by Electric Current, 4, 12, 20, 859 De-electrifying Ebonite, 216 Deflecting Field on Galvanometer Needle, When Uniform, 80 — • and Controlling Forces on Gal- vanometer Needle, 70, 81, 102, 111 Deflecting Force and Galvanometer Needle, Methods of Keeping Angle between Constant, 113 Force on Galvanometer Needle, When Current Directly Pro- portional to, 70, 137, 147 Force, When Proportional to Sine of Angle between Body and Controlling Force, 112 Deflection, Angular, of Magnifying Spring Ammeter Propor- tional to Current, 137 Best, to use with Tangent Galvanometer, 90 of Galvanometer Needls and Current Connection l«e- tween, 45, 84, 112, 124. 127 of Magnet by Electric Current, 3, 5, 34, 69 of Tangent Galvanometer Inde- pendent of Strength and Length of Needle, 91 on Bridge Galvanometer, Mean- ing of, 253 Deflectional Electrometer, Principle of, 162 Voltmeter, Calibrating, 183 Wattmeter, 332 Deflections of Tangent Gah^anometer Controlled only by Earth's Magnetism, Values in Am- peres of, 102 Density, Current, Definition of, 483 Electric, 224-231 of Copper, Variation of Specific Resistance with, 258, Note, 312 Quantity, and Potential, Ex- amples Showing Difllerence Between. 226 Depolariser, First Use of, 423 of Daniell's Cell, 423 of Dry Cells, 458, 459. ELB 617 Differential Galvanometer, 288. {See al$o Galvanometer, Differen- tial.) Gearing of Supply Meter, 840 Direct Reading Galvanometer, Defini- tion of, 127 — Reading Electrostatic Voltmeter, Ck)nstruction of Scale for, 180 Direction of Current, Meaning and Definition of, 2, 81 of Current, How to Reverse without altering Value of, 87 — of Current, when Necessary to Know, 184 of Current Shown with Per- manent Magnet, Magnifying Spring, and Moving Coil Am- meters, 134, 18<}, 145 Disconnecting Ammeter, Result of, 181 183 Voltme'ter, Result of, 181, 183 Dissimilar Magnetic Poles, Action between, 69 Distribution of Charge, 224 of Magnetism in Magnet, 63 of Potential in Batteiy, 874 Dom, Ohm Determined by, 582 Dry Cells, 457-462 Duncan, Rowland, and Kimball, Ohm Determined by, 583 Dynamo and Galvanic Cells, Com- parative Cost of Producing Electric Energy with, 482- 491 Cost of Producing Board of Trade Unit with, 488 Dyne, Definition of, NoUy 317 E " Earth," Definition of, 162 Potentials of Terminals of Cell Relatively to, 875 Earth's Controlling Force on Tangent Galvanometer, Variation of, with Place and Year, 103 Electrification, 160 Magnetic Field, Method of Neu- tralising, 78 '~— Magnetic Force, Disturbing Ac- tion of, on Another Mag- netic Field, 77 Potential, Arbitrary Value of, 160 j:arthing. Definition of, 162 Ebonite, Electrification of, 214 B.C.O. Dry Cell, 459. {See also Cell, E.O.C. Dry.) Bddy Currents, Meaning of, 147 Edison-Lalande Cell, 462. {See also Cell, Edison-Lalande.) Efficiency, Definition of, 405 How Expressed, 405 — Commercial, of Generator and of Motor, 406 Commercial, of Transmission, 409 Electrical, of Generator and of Motor, 406 Electrical, and Ratio of Power Received to Maximum Power Receivable, 412 Electrical, Obtained with Given Number of Cells Arranged to Give Greatest Power to Fixed External Circuit, 548 Electrical, of Transmission of Energy, 409 High Electrical, How to Trans- mit Power with, 410 Electric Arc {See Arc.) " Charge. (See Charge.) Circuit. {See Circuit.) Conductivity. (5ee Conductivity.) Conductor. {See Conductor.) Current. {See Current.) Density. {See Density, Electric.) Energy. {See ^nergy, Electric.) Lighting. {See Lighting, Elec- tric.) Potential. (See Potential) Power. {See Power.) Resistance. {See Resistance.) Spark Proves Existence of P.D., 161 Transmission. (Se« Transmission, Electric.) Electrical Appamtus Enclosed in Conducting Case, 197 Efficiency. (See Efficiency, Elec- trical) Standards. (5^e Standards, Elec- trical.) Units. (See Units, Electrical.) Electricity, Gnarge of. E.M.P. ElectriflcfttioD by Conduction and Indaction, Definition of, 218 of Bodv, Alteration of Potential with Amount of, 209 of Body, Testing Sign of, 215, 221 of Ebonite and Cat's Fur when Bubbed Together, 216 of the Earth. 160 of Leaves of Gold-leaf Electro- scope, 221 Electrochemical Equivalents of Copper and Zinc, 27, 28 Electro-Dynamometer, Principle of, 676 Electrolysis, Faraday's Ex^ieriments on, 27 of Dilute Sulphuric Acid, 82, Note, 62 Electrolyte, Decomposed into lous, 83 Electrolytic Action Produced in Given Time by Given Cur- rent, Conditions Governing Amount of, 27, 488 Electromagnet, Description of, 10, 17 Electromagnetic System of Units, Absolute, 671. ('See aho Absolute Electromagnetic System.) Electrometer, Ayrton and Mather Zero, 164, 181. (5ee also Voltmeter, Zero Electro- static.) Zero Type of, 168 Electrometers, Types of, 162 Electromotive Force. (See B.M.F.) Electromotor and Thermo-pile, Use of, for (Conversion of Energy, 2^o<e, 563 Series or Single Circuit, Defin- ition of, NoU, 371 Electronegative and Electropositive Ions, Definition of, 33 Electroscope, Gold-leaf, 191-196, 219- Gold-leaf, Calibration of, 194 Gold-leaf, Construction of, 192 Gold-leaf, Divergence of Leaves and Diameter of Case, 195 Gold-leaf, Law of. Conditions Governing, 194 Gold-leaf, P.D. between Leaves and their Divergence, 194 Gold-leaf, Precaution when Not in Use 193 Gold-leaf, 'sensibility of, 194 Gold-leaf, Testing Sign of Charge and Potential with, 219 Gold-leai; When Used, 191 Electroscopes with Lead Foil Leaves, Wnen Used, 196 Electrostatic Action, Exterior, Poten- tial Inside Closed C!onductor Due to, 197 Action, Exterior, Produces no Force Inside Closed Conduc- tor, 196 Action, Inside, Screening Out- side Space from, 222 System of Units, Absolute, 571 Voltmeter, Zero, 164, 179 Element, Simple Voltaic (See Simple Voltaic Element.) Elihu Thomson Joulemeter. (Sec Joulemeter, Thomson.) E.M.F. Back, Change of, and Varia- tion of Current. 872 Back, Definition of, 371 Back, of External Circuit Re- ceiving Maximum Power fh)m Given Current-Genera- tor, 893 Back, in Simple Voltaic Element, Cause of, 420 Back, in Simple Voltaic Element, Experiment to Find Seat of, 421 Back, in Smee's Cell, 482 '~— Back, Methods of Measuring, 871 Back, of Circuit Receiving Maxi- mum Power from Given Current-Generator, 893 Back of Electric Arc, Difficulty of Determining, 872 Back, to Produce most Rapid Transformation of Energy, 393-895 Constant, 622 of Battery, Definition of, 861 of Battery, Conditions Govern- ing, 861 of Battery, Definition of, 361 of Battery, Measuring, 365 of Battery, P.D. between Ter- minals, Resistance and Cur- rent, 864, 880-888 E.M.FS. INDEX. ENE 619 E.M.F. of Gell Independent of Size and Shape of Plates, 862-364 of Cell, Measorement of, 862, 866,477 of CelL When Eqnal to Terminal P.D., 622 of Bnnsen's Cell, 444 of Bomley Dry Cell, 460 of Clark's Cell, 467, 470, 474* 588,689,694 of Clark's Cell, Effect of Send- ing too iMtgid a Corrent on. ingt 477 of Claik's Cell, Potentiometer Method of Oradoating Volt- meter in terms of, 516 of Clark's Cell, Temperatore Variation of, 475 of Clark's Cell, Temperature Variation of. Affected by Method of Construction, 475 of Daniell's Cell, and of Modifi- cations, 426, 480, 478, 539 «^ of Daniell's Cell Calculated from Chemical Action, 478 of Daniell's Cell, Method of Maintaining Constant, 427 of Daniell's Cell, Variation of, witii Density of Solutions and Temperature, 426 of B.C.C. Cell, 460 of Edison-Lalande Cell, 464 of Oassner Dry Cell, 458 of Oroye's Cell, 440 of Grove's Cell Caleidated from Chemical Action, 480 of Grove's Cell Diminishes with Use, 441 of Hellesen Dry Cell, 469 of Leclanch^ Cell, and of Modifi- cations, 451 of Obach Dry Cell, 462 of Potassium Bichromate Cell, 446 of Simple Voltaic Element, Causes of Diminution of, 420 of Simple Voltaic Element, Ex- penment to Show Fall of, whenOurrent Sent, 420 of Smee's Cell, Calculating, 482 E.M.Fs. of Cells, Comparing, 502-510 E.M.F. of Any Current-Generator, Definition of, 869 — of Current-Genei-ator, Increase of, with Power Transmitted for Same Efficiency, 410 of Current-Generator, Measuring when Variable, 869 of External Circuit, Receiving Maximum Power from Given Current-Generator, 893 Eneigy, Board of Trade Unit of, 849,488,491 Chemical, Apparatus for Trans- forming, into Electric Energy, Chemical, Conveited into Elec- tric Energy per Second per Ampere in Daniell's Cell, 478 Chemical, Conversion of Elec- tric Energy into, 815 Chemical, Bate at which Con- verted into Electric Energy in Cell, 861, 380, 382, 883 Electric, Abstraction of, from Circuit by Current-Genera- tors, 871, 881 Electric, Apparatus for Con- verting into Other Non-Heat Energy, 315, 871 Electric, Apparatus for Intro- ducing into Circuit, 858, 359 Electric Comparative CoHt of Producing with Galvanic Cells and with Dynamo, 482- 491 Electric, Heat, and Mechanical, Conversion of, 814 Electric, Conversion of Heat Energy into, with Thermo- {Hie, Note, 563 Electrical Efficiency of Trans- mission of, 409 Electrical Efficiency of Ti-ans- mission, How to Make Large, 410 Electric, Liberated by Chemical Action in Cell, Calculation of B.M.F. from, 477 Electric, Measuring Amount of, Given to Circuit, 334-349 Electric, Measuring Heat Equi- valent of, 319 Electric, Meter. EXA Energy, Electric, Unit of, 817, 849 ——Heat, Production of, in Trans- formation of Energy, 404, 411 Heat, Rate of Conversion of Electric Energy into, 818- 824, 870, 880-384 Mechanical, Conversion of Energy of Current into, 814 —^Transmission o^ Methods of, 862, 854, 856, 857 Equilibrium of Galvanometer Needle, CondiUons of, 82, 111 Erg, Definition of, NoU, 817 Meter, 884 Ergs p^r Second, Value of Watt in, 826 Value of Joule and Board of Trade Unit in, 817, 840 Evershed Gravity Control Ammeter, Latest Form, 142 Gravity Control Ammeter, Scale of, 144 Examples on E.M.F. of Batteries, Ixxxi-lxxxvii ; 867-868 on Consumption of Materials in Daniel Is Cells, cxiii-cxvii ; 436-487 on Grove's Cells, cxviii-cxxiv ; 442-443 on Consumption of Materials in Leclanch6 Cells, cxxxi- cxxxv; 456-467 on Consumption of Materials in Potassium Bichromate Cells, cxxv-cxxx ; 448-449 on Maximum Current through Cell, Cell not Abstracting Energy from Circuit, xcvi ; 385 on Measniing Resistances of Cells, cxxxvi-cxli ; 501-502 on An-angements of Cells, clxv- clxix ; 642-644 on Arrangements of Cells to Send Maximum Current tlirough Given External Re- sistance, clxx-clxxiii ; 648- 649 on Safe Arrangement of Cells, clxxx-clxxxiii ; 561-562 on Least Number of Cells for Given Current and P.D., clxxiv-clxxv ; 562-658 on Least Number of Cells to Give Mxed Power to Given External Circuit, clxxvi, clxxvii; 654-556; clxxviii, clxxix ; 658-559 — on Direction of Current, x-xii ; 87 I Examples on Currents in Parallel I Conductors, liii ; 296 on Work done by Current, i Ix-lxiii; 816-817 : on E.M.F., and Back B.M.F., of : Generators and Motors, I Ixxxvlii-xcv ; 372-874 ! on Comparing E.M.Fs. of Generators, cxlii-czlviii ; 606-607 I on Efficiencies of Generators and i Motors, civ-cix ; 406-408 on Efficiency of Electric Trans- mission of Energy, cx-«xii; I 416-417 -^ on Electrolysis, I-ix ; 29-31 I on Glow Lami» in Parallel and ; Tel^raph Lines in Parallel, clii-clxiv ; 628-686 on Heat Equivalent of Electric Energy, ixiv, Ixv; 324 on Clock Joulemeter, Ixxiv, Ixxv ; 860 on Cost of Electric Ligliting, Ixxvi-lxxx ; 861-852 on Potential, Quantity, and I Density, 226-281 on Electric Power, Ixvi-lxx ; 327 -328 on Maximum Power Received by Whole, or Part, of External Circuit, xcvii-c ; 896-897 on Way in which Power Received by Whole, or Part, of Ex- ternal Circuit Varies from Maximum, ci-ciii ; 403-404 on Units of P.D. and Resistance, xxii-xxix; 176-176 on Resistance, xxxv-xlvi ; 271- 274 on Using Resistances with Voltmeters, xxx, xxxi ; 187- 188 on Combined Resistance, 1-lii ; 294 on Shunts, xlvii-xlix ; 291 on Universal Shunts, Ivii-lix; 810-811 on Increase of Main Current on Applying Shunt, liv-lvi ; 302 — on Shunting Galvanometers, cxlix-cli ; 623-624 — on Tangent Galvanometer, xiii- XV ; 101-102 ; xvi-xxi ; 104-107 "— on Using a Voltmeter and Resist- ance as Ammeter, xxxli, xxxiii ; 190 on Wattmeters Ixzi-lxxiil ; 888- 334 — on Wheatstone's Bridge, xxziv; 268 £XP INDEX GAL 621 Experiments, Graphically Recording Results of, 50-62 Importance of Changing only One Variable at Once in, 254 External Circuit. {See Circuit, Bxtemal.) P Farad, Definition of, 679 Faraday, Experiments on Electro- lysis by, 27 Experiments on Induction by, 218 Fault Testing in Telegraph Lines by Bright, Siemens, and Yailey, 569 Feeders, Definition of, 526 Fibre and Pivot Suspensions, of Gal- vanometer Needle, 110 Field of Thomson Joulemeter, 845 Coils of Thomson Joulemeter, 845 Controlling. (See Controlling Field.) Deflecting. (See Deflecting Field.) l^Iagnetic (See Magnetic Field.) Mapping out of. (See Mapping out Field.) of Motor, Definition of, 842 Uniform Magnetic. {See Uni- form Magnetic Field.) Filings for Magnetic Lines of Force Diagrams, Preparation of, 505 Majiping out Lines of Force with, 71-75, 77 Fletcher, Ohm Determined by, 583 Flow of Water, Connection between Bate of, and Loss of Head, 168 Fluid Pressure, Distribution of, Com- pared with Distribution of Potential along Conductor, 167 Foot Pounds per Second, Value of Watt in, 326 Pounds. Value of Board of Trade Unit, Joule, and Erg in, 817, 849 Force between Coils of Clock Joule- meter Compared with Grav- ity, 836 - — between Conductor and Magnet, Action of, 8, 129 Controlling. {See Controlling Force.) '~— Deflecting. {See Deflecting Force.) Forte of Detachment In Magnetic Experiments Aflfected by Character of Surfaces, 66 Electromotive. (See E.M.F.) Exerted and Position of Coil in Weston Milammeter, 147 Exerted by Magnets, 63 Exerted on Electric Conductor by Magnet, Employment of, 130 Gauss's Absolute Unit of, 671 Lines of. OAL Galnmometer. Oalflmitiiig, on Bine Principle, Necessity for Cur- rent Bemaining Constant while, 124 Calibrating, on Bine Principle wben Needle Pivoted or Suspended, 120-128 Calibration of. Absolute and ReUtive, Meaning of, 46 Calibration Curve of, 52 Compounding Forces in, 80 Construction of, having Angu- lar Deflection Directly Pro- portional to Current, 124 Controlling Field on Needle having Very Small Defleo* tions, 120 Controlling and Deflecting Fields on Needle, When Uniform, 80, 81, 126 Controlling and Deflecting Forces on Needle of, 70, 81, 102, 111 d'Arsonval, Modifications of, 144-161 d' Arson val. Principle of, 130 Definition of, Note, 48 Deflecting Force on Needle, Directly Proportional to Current, 70, 187, 147 Deflecting Force on Needle, When Proportional to Sine of Angle between Needle and Controlling Force, 112 Deflection of Needle of, and Current, Connection between, 45, 84, 112, 124, 127 Deflection of Needle, and Cur- rent, Methods of Producing Direct Proportionality Be- tween, 124 Differential, 288 Differential, Conditions for No Deflection when One Coil is Shunted, 812 Differential, Obtaining Equality of Magnetic EHects, and EquaU^ of Resistance of Wire of Coils, 240 Differential, Use of Shunts with, 311 Direct Reading, Definition of, 127 High Resistance, Why Used for P.D. Measurements, 178 Law of, 44, 69 Mather and Walmsley Proiwr- tional, 125 Moving Coil, 129. (See alto Ammeter, Moving Coil.) Needle, Conditions of Equi- Ubrinm of, 82, 111 Galvanometer Needle and Deflecting Force, Methods of Keeping Angle between Constant, 113 Needle, Why Given Deflection of. Occurs for Given Current, 60 Needle, Pivot, and Filwe Sus- pensions o^ 110 P.Ds. Measured with, 176 for P.D. Measurements, Best Form of, 178 Proportional, of Mather and Walmsley, 125 Proportional, Types of, 124, 147 and Resistance, Measuring F.Ds. with, 176 and Resistances, Comparing E.M.FS. of CeUs with, 503- 505 Resistances Compared with, 177 Resultant Force Acting on Needle of, 81 Scale Divided into Degrees, Dis- advantages of, 58 Scale Giving Relative Strengths of Currents, Construction of, 59 Scale Giving Relative Strengths of Currents, Subdividing Angular Spaces of, 60 Sensitiveness of; Methods of In- creasing, 44 Sine, Principle of, and Usual Method of Constructing, 118, 119 Sine, Use of. (See Galvanometer, Calibrating on Sine Principle.) Suspensions, Preparation and Use of Silk for, 666 Tangent, 88 Tangent, Axis of Needle and Plane of Coil of, Test for Parallelism between, 86 Tangent, Calibrating any Gal- vanometer by Comparison with, 108 Tangent, Calibration Curve of, 84 Tangent, Coll of, Acljusting, 85 Tangent, Coil Giving Greatest Sensibility, 100 Tangent, Coil of. Why Circular, 107 TaTigpnf^ Coil of. Why Unifji?,*^ Tiiii>r)di?t, CiJtiiiLjitit for A A*. li>lJl-Jf>00, 101 TjiijjjrH.iit, ToUil Coutroljfuj* Force nn KeefHp, 104 Tiiriyr^iit^ DeJ1t?t:t1on in Amperes Miliuii €<iiiLP(>lled only by Kartli'» lifaigi)^ti^?in, 103 GAL INDEX. 