None
CAR Bridge, Wheatstone's, Balance with, Definition of, 245 Wheatstone's, Desirability of Using Key with, 260 Wheatstone's, Devices for Ex- pediting Use of, 258 Wheatstone's, Galvanometer and Battery Interchangeable in, 245 Wheatstone's, Proofs of Law of, 248 Wheatstone's, Measuring Very Large and Very Small Re- sistances by, 284 Wheatstone's, Using, 245 Wheatstone's, of, 285 Wheatstone's, Methods of Portable Forms 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 Sensibility of, 285 Wheatstone's, Subdivision of Wire of, into Lengths having Equal Resistances, 515 Wheatstone's, Value of Coils for, 288 Wire, Material for, 247 Wire, Advantage of Using Long, 240 Bright, Sir Charles, Proposes Karnes Ohmad and Volt, 578, 576 British Association Committee for Determining Unit of Re- sistance, Method Used by, 572 — — Association Committee, Ohm Determined by, 581 Brush Discharge Proves Existence of P.D., 161 Bi-ushes of Elihu Thomson Joule- meter, 848 Bunsen's Cell. (See Cell, Bunsen's.) Burnley Dry Cell, 459. (See cUso Cell, B.C.C. GEL 607 Carbons for Buusen's Gell, Mauufac- ture of, 444 Carpentier's Proportional Galvano- meter. Principle of, 125 Case, Gondnctlng. (pee Conducting Gase ) Cathode, Definition of, 24, 88 — for Silver Voltameter, Descrip- tion of, 28, 26 — Weights of Metals Deposited on, 27 Canstic Potash Gonsnmed in Edison- Lalande Cell per Board of Trade Unit Produced, Weight and Cost of, 466, 487 Potash Consumed In Edison- Lalande Cell per Hour per 1,000 Amperes, 484 Cell, AmaljipBimating Zinc Plate of, 480 Aylmer Ledanchd, 466 Bunsen's, 443 Bunsen's, Compared with Orove's Cell, 443 Bunsen's, B.M.P. of, 444 Burnley Dry, 469. (See also Cell, B.0.0. Dry.) Callaud, 482 Chemical Action in, B.M.F. Calculated from, 477-482 Chemical Actions in Different Types of, 418, 424, 427, 488, 489.446,460,468,478 Chromic Acid, 446-448 Chromic Acid, Weights and Cost of Materials Consumed in, per Board of Trade Unit Pro- duced, 487 Chromic Add, Weights of Materials Consumed in, per Hour per 1,000 Amperes, 484 Clark's, 466-477, 616-621, 588, 680, 600, 694, 697-699 — — Clark's, Board of Trade Form of, 470 Clark's, Board of Trade Specifi- cation for, 467, 497 Clark's, Boiard of Trade Specifi- cation, Notes to, 470, 492 Clark's, Cooper's Modification of Kahle's H Form of, 474 Clark's, Definition of, 467, 697 Clark's, Effect on E.M.F. of Sending too Large a Current, 477 Clark's, B.M.F. of, 467, 470, 474, 588, 689. 694 Clark's, B.M.F. of. Temperature Variation of, 475 Clark's, B.M.F. of. Temperature Variation of. Affected hy Method of Construction, 475 Cell, Clark's, How to Set up, 468, 698 Clark's, Glazebrook's Notes to Specification of, 470, 592 Clark's, Kahle'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, 616-619 Clark's Potentiometer Method of Testing Accuracy of Volt- meter Scale with, 610 Clark's, Preparation of Materials for, 467, 697 Clark's, Bayleigh's H Form of, 466 Clark's, Relative advantages of Two Types of, 474 Clark's, Resistuice Advisable for Use with, 477, 611 Clark's, with Fixed Resistance as Standard of Current, 619 Copper - Zinc-Dilute - Sulphuric • Acid. (See Simple Voltaic Element) — r Daniell's, 423-436, 461, 478, 484, 486 Daniell's, Chemical Action in, 424, 427, 478 Daniell's, Chemical Energy Converted into Electric Energy in, per Second per Ampere, 478 Daniell s. Compared with Ledanch6 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.F. of. Calculated from Chemical Action, 478 Daniell's, E.M.F. of, Method of Maintaining Constant, 427 Daniell's, B.M.F. of, Values of, 426, 478, 639 Daniell's, E.M.F., Variation of, with Density of Solutions and Temperature, 426 Daniell's, Forms, of, 481. (See also Cell, Callaud, Gravity, Meidinger, Minotto.) DanielPs, Local Actions in, 429, 430 Daniell's, Precautions in Con- struction of, 426, 428, 430, 481 608 CEL PRAOTICAL ELEOTRICITT. CBL Cell, Daniell's, Precantions when Us- inff. 426, 427. 485 Danieli's, Prevention of Copper Sulphate Diffkuing throngh Porous Partition of, 490 Daniell's, Prevention of Forma- tion of Guprio Oxide in, 430 — — Daniell's, Resistance Varies with Constancy and Portability, 481 Daniell's, Resistance of. Varies with Temperatnre, 486 — Daniell's, Resistances of Various Forms of, 485 Daniell's, Weight and Cost of Materials Consumed in, per Board of Trade Unit Pro- daced, 486 Daniell's, Weights of Materials Consumed per Hour per 1,000 Amperes, 484 •^— Daniell's, Zmo Consumed per Hour per Ampere, 424 -— Daniell's, Zinc Sulphate Formed per Hour per Ampere, 426 De ia Rue Silver Chloride, Un- suitability of, for Practical Use, 477 Depolariser First Used in, 428 E.O.C. Dry, 469 B.C.C. Dry, Compared Hellesen Cell, 460 B.C.C. Dry, E.M.F. of, 460 Edison-Lalande, 462-465 Edison-Lalande, Chemical tion in, 463 — ^ Edison-Lalande, Depolariser of, 462 Edison-Lalande, E.M.F. of, 464 Edison-Lalande, Resistance of, 464 Edison-Lalande, Weights and Cost of Materials Consumed in, per Board of Trade Unit Produced, 465, 487 — Edison-Lalande, Weights of Materials Consumed per Hour per 1,000 Amperes, 484 with E.M.F. Constant Used with Known Resistance for Cali- brating Galvanometer, 621 E.M.F. of. Calculated from Chemical Action in, 477-482 — — E.M.F. of, Compared with E.M.F. of Standard Cell, 502-610. E.M.F. of. Determined, with Voltmeter, 862. 866 with E.M.F. Helping Current May Abstract Energy from Circnit. 882 with Ac- Cell, E.M.F. of, P.D. between Ter- minals, Resistance, and Cur- rent, 364, 880 E.M.F. of, When Equal to Ter- minal P.D., 622 E.M.F. of Different Types of, 426, 440, 444, 446, 451, 458, 459, 460. 462, 464, 467 E.M.Fs. of, Independent of Shape and Size of Plates, 362-364 with Back E.M.F. Abstracts Energy firom Circuit, 871, 383 Gassner Dry, 468 Gassner Dry, Commercial Im- practicability of, 458 Gassner Dry, E.M.F. of. 458 Gravity Daniell's, 431-483, 436 Gravity Daniell's, Precautions when Using, 482. 486 Grove's, 438-442, 480, 484, 486, 627, 650-662 Grove's, Chemical Action in, 488,439 Grove's, Compared with Bun- sen's Cell, 443 Grove's, Depolariser of, 438, 439 Grove's, E.M.F. of, 440 Grove's, E.M.F. Diminishes with Use of, 441 Grove's, E.MF. of. Calculated from Chemical Action, 480 Grove's, Formerly used in Tele- graphy, 527 Grove's, Nitric Acid Used Up per Hour per Am^e, 440 Grove's, Nitric Peroxida Formed per Hour per Ampere, 440 Grove's, Precautions when Us- ing, 439, 441 Grove's, Resistance of, 440 Grove's, Resistance Increases with yse of, 441 Grove's, Sulphuric Acid Cou- sumed'^rHour per Ampere, 440 Grove's, Water Formed per Hour per Ampere, 440 Grove's, Weights and Cost of Materials Consumed in, per Hoard of Trade Unit Pro- duced, 486 Grove's, Weights of Materials Consumed per Hour per 1,000 Amperes, 484 Grove's, Zino Sulphate Formed per Hour per Ampere, 440 Grove's, Zinc consumed per Hour per Ampere, 440 Hellesen Diy, 458 Hellesen Drj, E.M.F. of, 459 GEL INDEX. GEL 609 Gell, Lalande-Gliaperon, 462 Lalande-Chaperon, Defects of, 468 Leclanch^, 449-456, 484, 487 Leclancfa^, Weights and Gost of Materials Gonsuined in, per Board of Trade Unit Pro- duced. 487 Leclanche, Weights of Materials Gonsumed per Hour per 1,000 Amperes, 484 Ledanch^, When Used, 461 I^clanchi Agglomerate, 452 Leclanch6 Agglomerate, Forma- tiou of the Agglomerate, 462 Leclanchi-Aylmer, 456 Leclanch^-l^rbier, 452-455 Leclanch^-Barbier, Advantages of, 454 Leclanch^-Barbier, Gomposition of Salt Used in, 454 Leclanch^, Ghemical Action in, 450 Leclanch^, Gompared with Danjell's Gell, 461 Leclanch6, Depolariser of, 450 Leclanch6, Disadvantages of, 452 Leclanch^, B.M.F. of, 451 Leclanch^, Modifications of, 452-456 — - Leclanch6, Precautions in Gon- stmction of, 451 Local Action, How Gaused in, 429,480 Mari^Davy Mercuric Sulphate, Unsuitability of, for Practi- cal Use, 477 Meidingcr, 431 Minotto's, 483 Obach Dry, 460 Obach Dry, E.M.P. of, 462 P.D. between Terminals of, Gonstant, when Low Internal Besistance, 622 P.D. between Terminals of. Diagram Showing None, 384 Polarisation of. Definition of, 364 Positive Plate of, Definition of, 376 Positive Terminal of, Definition of, 876 — Potassium Bichromate, 445-448, 484, 487 — :- Potassium Bichromate, Ghemi- cal Action in, 445 — — Potassium Bichromate, E.M.F. of, 446 — — Potassium Bichromate, Precau- tions when Using, 445, 447 U Gell, Potassium Bichromate, Weights and Gost of Materials Gon- snmed in, per Board of Trade Unit Produced, 487 — Potassium Bichromate, Weights of Materials Gonsumed per Hour per 1,000 Amperes, 484 Putassium Bichromate, When Used, 447 Potassium Bichromate, with Porous Pot, 446 Putassium Bichromate, without Porous Pot, 445 Potential in, Diagrams Showing Distribution of, 874-381, 884 Potential in. Uncertainty as to Method of Variation of, 874 Potentials of Terminals of, Belatively to Earth, 875 Rate at which Ghemical Energy is Converted into Electric Energy in, 361, 880, 882, 383 Rate at which Electric Energy is Qiven to, or Taken flrom, Outeide Gircuit by, 816, 380, 882,883 Rat6 at which Electric Eneiigy is Gon verted into Heat in, " 370,380-384 Resistence of, Ghoice of Method for Measuring, 498 Resistance of, Conditions Gov- erning, 434 Resistance of, Measuring when Not Very Small, 498 Resistance of. Measuring when Very Small, 866, 492 Safety LimiUtion of Maximum Ourrent for, 559 Secondary. (See Accumulator.) Short-Gircuiting, How to Avoid Possibility of, when Using Mercury Switch-board, 540 Smee's, 423, 482 Smee's, Production of Back E.M.F. in, 482 Storage. (See Accumulator.) Zinc and Copper, Signs of Ter* minals and Plates of, 876 Cells Abstracting Energy AK>m Out* side Circuit, Diagram Show- ing, 884, 385 Ari-angemente of, 636 Arrangement of Gircuit Re- quiring Least Number of, to Give Fixed Power to External Portion^ 555 Arranging Given Number of, for Maximum Current, 545 Carbon Plate of, 443, 445, 450, 452, 458, 460, 401 BIO CEL PRACTICAL ELECTRICITY. CHR ^ Cells,' Coitamercial Value of Waste Products of, 4S8, 400 ^— Conditions for Commei*cial Use of, for Electric Lighting, 401 Copper Oxide Plate of; 462, 468 Copper Plate of, 410, 422, 481, 488,485 - — Cost of Producing Board of Trade Unit with, 482, 488 — — Coupling with Mercury Switch* board. Methods of, 641 — ^Distribution of Potential in, 874-880 -— Dry, 457-462 Dry, Advantages of, 457, 458 — Dry, Early Attempts at Con- struction of, 457 and Dvnamo, Comparative Cost of Producing Electric Encisy with, 482-401 E.M.Fs. of. Comparing, 502-510 Joined in Parallel, Beoies, and Parallel Series 586-587 — — Joined in Parallel, E.M.F. of Battery Formed of, 688 Joined in Series, Ourf» Connect- ing Number of, and Current, 546 Joined In Series, B.M.F. of Battery Formed of, 587 Leclanch6, Leclanch6-Barbier, and Aylmer-LeclanchS, Com- parison between, 456 ——Local Action in. Method of Preventing, 420 Minimum Number of, for De- livering Qiven Power, 553- 557 Minimum Number oi^ to Pro- duce Given. Current and P.D., 540 Negative Plate of, 410, 423, 431, 488, 485, 438, 443, 445, 450, 452, 453, 455, 460, 461, 462 — > Number of, in Series and Rate of Chemical Action, 360 — ^ Platinum Plate o^ 423, 488, 482 ■' — Polarising Rapidly, Measuring Resistance of, 408 Positive or Zinc Plate of, 410, 423, 431, 433, 435, 438, 445, 450, 454, 455, 458, 450, 460, 461. 462, 463 <— — Potential Lost in, Oraphical Representation of, 870 Prices of Materials Consumed in, 485 ' Resistances of. Methods of Measuring, 402-500. ^^- in Series, Diagram Showing Dis- tribution of Potential in, 876 Cells, Birfgiti Fluid, 418, 445, 450, 462 for Telegraphy, 527 Two Fluid, 423, 433, 438, 448, 445. 466 Use of, for Electric Lighting, 488-401 Waste of Energy in, 480, 401 C.O.S. Units Adopted for Electrical Measurements, 470, 576, 578, 588, 587, 503 Units, Value of Ampere, Ohm, and Volt in, 470, 578, £76, 578, 570, 588, 587, 503 Charm, Distribution of, 224 — - Electric, Meaning of, 208 of Body, Variation of Potential with, 208, 200 Sign of, 214-231 Charged Body, Introduction of, Into Conductor, 218 Cliemlcal Action in Cell, Calculation of B.M.F. from, 477-482 Action in Daniell's Cell, 424, 427, 478 ——Action in Bdison-Lalande Cell, 468 Action In Grove's Cell, 438, 439 Action in Leclanch^ Cell, 450 Action in Potassium Bichromate Cell, 445 Action in Preparation of Chro- mium Trioxide, 447 Action in SimpleVoltaie Element, 418 Action in Sulphuric Acid Volta- meter, 88 Action of Current, Rate of, In- dependent of Sixe and Shape of Apparatus, 17 Action Produced by One Ampere per Second, 23, 20, 424, 440, 465, 478, 484, 588, 508 .— — Action, Rate of, and Number of Cells in Series, 860 , Action, Rate of Production of. Proportional to Current Pass- ing, 14, 22, 861 Energy, Conversion of Electric Ener^ into. 315 : Energy Ck)nverted into Electric Energy per Second \)er Am- pere in Daniell's Cell, 478 Energy, Rate at which Converted into Electric Energy in Cell, 861, 380. 882, 383 Property of Current, Uses of, 9 Property of Current, Why Car- rent Strength Defined by, 14 Chrome Alum, Fonnation of, in Potassium Bichromate Cell, 448 CHB. INDBX, COI 611 Chromic Acid GeH. (See Cell, Fotassinm Bicliromate.) Acid. {Sea Chromium Trioxide.) Cliromium Trioxide Consumed in Cell per Board of Trade Unit Fro- daoed, Weight and Cost of, 487 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 Circuity Abstraction of Energy from, by Generators, 871, 881 Arrangement of. Requiring Jjeast Number of Cells to giye Fixed Fower to External Portion, 555 Back E.M.F. in, 870 Complete Elecmo, Description of, 852 Distribution of Potential in, 876 Distribution of Potential in, with KM.F. Oppgaing, 878 : — >- Electric, Analogies with, 854, Electric, Medoanical - Model IllufltFating, 866-867 -i— External. Arrangement of Bat- tery to Oive Maximum Cur- rent and Power to, 545 •: External, Arrangement of Part of, to Receive Maximum Fower, 893 External, Conditions Oovemtng Variation of Potential along, 874, 376 — External, E.M.F. of, to Receive Maximum Fower from Given Current Generator. 808 External, Rate at whiich Eneivy . Given to, or T^en from, by Generator, 358, 871, 880-388 -^^ External, Receiving Maximum Fower from Given Generator, 886-398 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 F.D. between Ends of, Coa<ttant, 287 Part of, in which Potential Diminishes in Direction- -of Current, 852. Part of, in which Potential Increases in Direction - -of. Current, S53 Circuit, Power Absorbed in, Exterior to Generator, 870 Raising Potential of Eleciaioity in, 858 Rate of Introduction of Electric Eneii^ into, 358 Rate of Production of Heat in, 81ft-327 Single, Definition of, 877 •^—Single, Uniformity of Current in, 877 Circuits, Parallel. Independence of Currents in, 625 Clark's Cell. (Su Cell, Clark's.) Clark, Latimer, Proposes Names Ohmad and Volt, 578,' 576 dock Joulemeter. {See Jouleraeter, Clock.) Coal Gas, Transmission of Energy by, 356 Coefficient, Temperature, and Specific Resistance of Conductor, Re- lation between, 267 Coefficients, Temnerature, of Resist- ance of Metals and Alloys, 264-267 Coil and Iron Core, Variation of Force between, irith Positions of, 187 Circular, Carrying Current, Lines of Force due to, 71 Large, Importance of, for Tangent Galvanometer, 100 Moving, of Ayrton and Mather's Ammeter, 148, 149 Moving, Shape of, to Obtain Greatest Torque, 148 Non-inductive Resistance, for Large Currents, 282 Pendulum, of Clock Joulemeter, 888 Plane oil and Axis of Needle, Test for Parallelism between , in Tangent Galvanometer, 86 — - Position of. and Force Exerted on, in Weston Milamnieter, 147 of Sine Galvanometer, Position of, 119 Spinning, Use of, for Deter- . raining Unit of Resistance, 572 Standard Resistance, 276 of Tangent Galvanometer, Ad- justment of, 85 of Tangent Gkdvanometer, Posi- tion of, 86 -r — of Tangent Galvanometer, Why Circular, 107 ■; Coils for Commercial Wheatstone'a Bridge, Values of, 284 612 cor PRACnOAIi BLfeCfTRICITT. CON Coils for DifTerentfal Galvanometer, Constraction of, 240 —— for Differential Galvanometer, Equality of Magnetic Effects and Equality of Resistance, 240 of Motor, 843 of Ohmmeter, 238 of One B.A. Unit of Besifctance, Verification of, 574 for PortableWheatstone's Bridge, Values of, 287 of Proportional Galvanometer, 126 for Resistance Boxes, Values of, 288 of Shunt Box, 295, 297 of Thomson Joulemeter, 841-345 — ~ Resistance, Description of, 40 Resistance, Earliest Form, 569 Resistance, Kind and Gauge of Wire Employed in, 281, 282 Resistance, Magnetic Action in, 281 Resistance, Mode of Winding, 280-288 Resistance, Specific 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 Gumbustion, Measurement of Heats of, 478, 481 Connnercial Efilcieucy of Generator, and of Blotor, Definition of, 406 Efficiency of Transmission, De- finition of, 409 Forms of Wattmeters, 831 Commutator, Descriptim of, 842 of Eliliu Thomson Joulemeter, 848 848 Comparing E.M.Fs. of Cells, 50*2-510 (Se0 also Measuring E.M.F.) P.Ds. by Current Method, 176 (Su aJso Measuring P.D.) Quantities of Electricity, 211 Resistances in Parallel by Differential Galvanometer, 238 — Resistances in Parallel by Wheat- stone's Brid£», 241-258 Resistances in Series, 177, 184, 186 — — Resistances by Simple Snbstita- tion,886 Comparing Resistances. CUJ? 613 Conductor with Current Fasafng and Magnet, Force Exerted Be> tween, 8, 129 Effect of Changing Shape of, on Cunent, 173 Electrified by Conduction or In- duction, 218 Equivalent, and Branch Cirouits, Conductivities of, 292, 293 No Electricity at Best Inside, 209 P.D. Maintained Constant be- tv9eea 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 Lepgth, 258-256 Resistance of. Varies with Material, 254, 257-262 Resistance of, Varies with Tem- perature, 238, 254, 262-271 Wamied by Current, 5, 8, 318 Conductors in Parallel, Combined Resistance of, 292 Parallel, Resistances of, and Currents Passing, 288 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 Coefilcients of, 267 With Negative Temperature Change of Resistance, 207, 269, 271, 812 With No Temperature Change of Resistance, 269 With Small Temperature Change of Resistance, 266-271 Constant and Uniform, Difference between, NoUf 153 — - E.M.F., 522 for Tangent Galvanometer, a.d. 1891-1900, 104 P.D., 622 Construction of Galvanometer Scale Giving Relative Current Strengths, 58 ConBtraction of Galvanometers with Angular Defiection Directly Proportional to Current, 124 of Plug Resistance Boxes, 277 of Shunt Boxes, 295, 304 of Sulphuric Acid Voltameter, 38 of Tangent Galvanometer Scale, 88 of Wheatstone's Bridge, 246 Controlling Field on Galvanometer Needle having Very Small Deflections, 126 Field on Galvanometer Needle, When Unifonn, 80, 81, 126 Force, Calibrating Sine Galvano- meter, by Altering Direction of, 128 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, ou Tkngent Gal- vanometer, Determination of, 104 Cooper's Modification of Eahle's H Foim of Clark's Cell, 474 Copper and Silver, Comparative Rates of Electric Deposition of, 28 Atomic Weight of, 27 Deposited in Voltameter, per Second, per Ampere, 27 Electrochemical Equivalent of. Variation of, with Area and Temperature, 28 Percentage Conductivity of. Definition of, 274 Plate of Cells, 419, 421, 481, 433, 485. (See also Plate, Copper. ) Relative Electric and Heat Conductivities of, 275 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 Tiude Unit Produced, Weight and Cost of, 465, 487 6U COP PBACTICAL SLBCTRICITT. CUR in in Copper Oxide OoDsnmed in Edison* Lalande Cell per Hour per 1,000 Amperes, 484 Oxide Plate of Cell, 462, 463 Sulphate consumed in Daniell's Cell per Board of Trade Unit Produced, Weij;ht and Cost of, 486 Sulphate Consumed in Danleirs Cell per Hour per 1,000 Amperes, 425, 484 Sulphate, Diffusion of, Daniell's Cell, 480 Sulphate, Heat Absorbed Decomposition of, 478 Voltameter, 10 Voltameter, When Used, 26 Cost and Weights of Materials Con- . sumed in Cells per Boaitl of Trade Unit Produced, 486, 487 Comparativc,'of Using Cells aiui Dynamo, 482 of Producing Board of Trade Unit, 488, 491 of Producing Board of Trade Unit, with . Battery, 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, 818, 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, 3, 5, 84,69 Direction of, in Cells, 423, 424, 427, 438, 439, 445, 446, 450, 463 — Direction of Flow, Definition o^ 2, 81 Current, Direction of, How Deter- mined, 84, 184 Direction of, and Magnetic Polarity, Connection be- tween, SO Dii^ection of. When Necessary. to Know, 184 Density, Definition of, 483 Electric, Compared with Cur- rent of Water, 2, 5, 13, 152, 318, 853, 854 Electric, What is Meant by, 2 of Gaa, Measurement of Distri- bution of Pressure in, 158 Generator, Arrangement of, to give Maximum Power to Ex ternal Circuit, 805 Generator, Commercial EflAc- iency of, 406 Generator, Electrical EflSciency of, 400 ' Generator with K.M.F. Helping May Abstract Energy, 881 Generator, E.M.F^ of, and Loss of Power in Electric Trans- mission, 410 Generator, EM.F. of, Definition of, 869 Generator, External Circuit Re- ceiving Maximum Power from, 885-895 Generator, Finding Circuit Re- ceiving Maximum Power from, 891 Generator, Measuring E.M.F. of, 369 Generator of Fixed E.M.F. and Resistance giving External Circuit Maximum Power, 889 Generator, Power Absorbed in Circuit Exterior to, 870 Generator, Power Developed by, 358 Generator, Power Developed l»y, Equals Current into E.M.F. of, 870 Generator with Variable E.M.F., 369 Generator, Work done by ,167,359 Heat Produced by, 5, 9, 318 Increase of, in Main by Apply- ing Shunt, 298 in Battery, P.D. between Ter- minals, E.M.F. and Resist- ance, 864 in Battery, Proportional to Chem- ical Action, 859 in Cell in Terms of P.D., E.M.F., and Resistance, 864, 880-883 in Circuit, P.D. between Ter- minals, and Power, 370 CUR INDEX, CXJR 615 Current in Circnit, Uniform Strength of, 162. 877 in Danielrs Cell, Variation of, with Temperatare, 480 in Galvanometer and Deflection of Needle, 45, 84, 112, 124, 127 in Galvanometer and Force Keeping Needle at Best, 70 in Tangent Galvanometer with Earth's Control, Formula Giving, 108 — in Generator, Ratio of, to Power Developed, 870 in Magnifying Spring Ammeter Proportional to Angular De- flection, 187 in Simple Voltaic Element, Cause of iMminution of, 421 - in Voltameter, Direction of, 88 Magnetisation of Iron by, 8, 5, 85 Maximum, for Cell, Safety Limitation of, 559 - — Maximum, through Given'Ex- temal Resistance, Arrange- ment of Given Number of Cdls 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 Cell and Known Resistance, 519 Measuring with Copper Volta- meter, 10, 26 Measuring with Silver Volta- meter, 23-26, 595 Measuring with Voltmeter and Fixed Resistance, 189 Measuring, Instruments for. (See Ammeter, Calorimeter, iilectromagnet. Galvano- meter, GsJvanoscope, Volta- meter.) Measuring Rate . of Heat Pro- duced by, 819 Measuring, Standard Resistance 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., Relation be- tween, 827 — — Primary, Direction of, in Expe- rimental Voltaic Element, 423 Current, Production of, 156. (SuoUb Battery, Cell, and Current- Generator.) Production of, between Twe Conductors, 161 Properties of, 8 Property of, Best to Measure Strength by, 20 — "— Proportional to Rate of Chemical Aetlon, 22, 861 Ratio of P.D. to. Constant for given Conductor, 170 Ratio of P.D. to, for given Conductor, Experimentally Determined, 171 Reversing Direction of, without Altering Value, 87 Secondary, Direction of, in Experimental Voltaic Ele- ment, 428 Strength, Definition of. 23 Unit of. (See Ampere.) Unit of, Aim of B.A. Commit- tee in Choosing, 576 Uses of Diflbrent Properties of, 9 Variation of Effect of Shunt on with Change of External Resistance, 299 Variation of Light of Glow Lamp with Change of, 490 Variation of, with Change of Back E.M.P., 372 of Water Coniitfired with Electric Current, 2, 5, 13, 152, 313, 363, 364 of Water, How Maintained, 156 of Water and Loss of Head, 163-156 of Water, Work Done by, 813 Electric, Work Done by, 813 Voltmeter." (See Voltmeter.) Currents, Eddy or Foucault, 147 in Armature or Blihu Thomson Joulemeter, Directions of, 344 in Batteries with Different Ar- rangements of Cells, 537 in Elihu Thomson Joulemeter Proportional to Magnetic Fields Produced, 846 in Parallel Circuits, Independ- ence of, 525 in Parallel Conductors, Ratio of, to Current in Main, 295 in 6hunt and Galvanometer, Ratio between, 290 in Shunt and Galvanometer Ratio of each to Whole Current, 290] Local, 429 616 CUR PRACTICAL ELECTRICITT. DIF Carrents Passing tlu'ough Two Con* ductora in ParaUel, Measure- ment of, 288 --~ Through Two Conductors in ParaUel Inversely Propor- tional to Resistances, 238 Onnre, Calibration. {See Calibration Curve.) ^— Connecting Galvanometer De- flection and Current, 62 — — Connecting Power Received by External Circuit with its Resistance, 401, 402 ^— Connecting Rate of Flow of Water with Loss of Head, 168 — — How General Cliaraeter of Re- sult Obtained Shown by, 56 ——.Recording Results of I^peri- meut for Calibrating Gal- vanometer, 62 — Showing Current Giving Maxi- mum Power to External Circuit, 887 Curves, Choice of Abscissie, Ordinates and Units for, 67 Connecting Variation of Resist- ance of Metals with Tem|)er-. ature, 264, 265 Drawing, on Squared Paper, 51 How Drawing of. Corrects Re- sults of Experiments, 55 Results of Intermediate Untried Experiments Obtainable fh>m, 55 Showing Tests on Three Types of LeclanchS Cell, 456 Cylinder, Zinc Plates of Cells in Form ' of, 431, 455, 461 Daniell's Cell. (See Cell, Daniell's.) Use of Depolariser, 423 D'Arsonval Galvanometer, Modifica- tions of, 144-151 •—— Galvanometer, Principle of, 130 Davy'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 — — Foi*ce 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 Magiiifyiiig Spring Ammeter Propor- tional to Curi-ent. 187 Best, to use with Tangent Galvanometer, 90 of Galvanometer Needl? and Current Connection l«- tween, 45, 84, 112, 124, 127 of Magnet by Electric Current^ 8, 5, 84, 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 Galvanometer Controlled only by Earth's Magnetism, Values in Am- Iteres of. ELB 617 Differential Galvanometer, 238. (See also Galvanometer, Differen- tial.) Gearing of Supply Meter, 840 Direct Readmg Galvanometer, Defini- tion of, 127 — - Beading Electrostatic Voltmeter, Gonstmction of Scale for, 180 Direction of Current, Meaning and Definition of, 2, 81 of Current, How to Reverse withont altering Value of, 87 — of Current, when Necessary to Enow, 184 of Current Shown with Per- manent Magnet, Magnifying Spring, and Moving Coil Am- meters, 134, 186, 145 Disconnecting Ammeter, Besnlt of, 181, 183 Voltmeter, Result of, 181, 183 Dissimilar Magnetic Poles, Action between, 69 Distribution of Charge, 224 of Magnetism in Magnet, 63 of Potential in Battery, 374 Dom, Ohm Determined by, 682 Dry Cells, 457-462 Duncan, Rowland, and Kimball, Ohm Determined by, 588 Dynamo and Galvanic Cells, Com- Eirative Cost of Producing lectric Energy with, 482- 491 Cost of Producing Board of Trade Unit with, 488 Dyne, Definition of, NoU^ 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, IGO Magnetic Field, Method of Neu- tralising, 78 — - Magnetic force. Disturbing Ac- tion of, on Another Mag- netic Field, 77 Potential, Arbitrary Value of, 160 Earthing, Definition of, 162 Ebonite, Electrification of, 214 B.C.O. Dry Cell, 459. {See also Cell, B.C.O. Dry.) Eddy Cnrrents, Meaning of, 147 V* Edison-Lalande Cell, 462. (See also Cell, Edison-Lalande.) Efiiciency, Definition of, 405 How Expressed, 405 — - Commei-cial, 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 Beceivable. 412 Electrical, Obtained with Given Number of Cells Arranged to Give Greatest Power to Fixed External Circuit, 548 Electrical, of Transmiaslon of Energy, 409 High Electrical, How to Trans- mit Power with, 410 Electric Arc {See Arc.) Charge. {See Charge.) Circuit (5« Circuit.) Conductivity. fSee Conductivity.) Conductor. {See Conductor.) Current. {See Current.) Density. {See Density, Electric.) Energy. {Su Energy, Electric.) Lighting. (See Lighting, Elec- tric) Potential {See Potential) Power. {See Power.) Resistance. {See Resistance.) Spark Proves Existence of P.D., 161 Transmission. (See Transmission, Electric.) Electrical Apparatus Enclosed in Conducting Case, 197 Efiiciency. {See Efiiciency, Elec-' tricaL) Standards. (See Standards, Elec- trical.) Units. (See Units, Electrical.) Electricity, Gnange of. B.M.F. Electrification by Conduction and Induction, Definition of, 218 of Body, Alteration of Potential with Amount of, 209 of Body, Testing Sign of, 215^ 221 of Ebonite and Cat's Fur when Rubbed Together, 216 of the Earth, 160 of Leaves of Qold-leaf Electro- Bcope, 221 Electrocheinical Equivalents of Copper and Zinc, 27, 28 Electro-Dynamometer, Principle of, 675 Electrolysis, Faraday's Experiments on, 27 of Dilute Sulphuric Acid, 32, Note, 62 Electrolyte, Decomposed into Ions, S3 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, 571. (See also Absolute Electromagnetic System.) Electrometer, Ayrton and Mather Zero, 164, 181. {See also Voltmeter, Zero Electro- static.) Zero Type of, 168 Electrometers, Types of, 162 Electromotivj) Force. (See E.M.F.) Electromotor and Thermo-pile, Use of, for Conversion of Energy, JTote, 563 Series or Single Circuit, Defin- ition of, NoU, 371 Electronegative and Electropositive Ions, Definition of, S3 Electroscope, Gold-leaf, 191-196, 219- 222 Gold-leaf, Calibration of, 194 Gold-leaf, Construction of, 192 Gold-leaf, Divergence of Leaves and Diameter uf 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 Qold-leaf, When Used, 191 Electroflcopes with Lead Foil Leaves, When Used, 196 Electrostatic Action, Exterior, Poten- tial Inside Closed Conductor 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 Elemenih^Bimple Voltaic. (See Simple Voltaic Element.) Elihu Thomson Joulemeter. (See Jonlemeter, 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 from Given CuiTent-Geuera- tor, 393 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, 371 Back, of Circuit Receiving Maxi- mum Power from Given Current-Generator, 893 Back of Electric Arc, Difficulty of Determining, 372 Back, to Produce most Rapiil Transformation of Bnei-gy, 393-395 Constant, 522 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, 364, 380-883 E.M.FS. ENE 619 E.M.F. of Cell Independent of Size and Shape of Plates, 802-864 of Cell, Measuremeut of, 862^ 865,477 of Cell, When Equal to Tenninal P.D., 622 of Bunsen's Cell, 444 of Burnley Dry CJell, 460 of Clark's Coll, 467, 470, 474, 588, 589, 594 of Clark's Cell, EflTect of Send- ing too Laige a Current on, 477 of Clark's Cell, Potentiometer Method of Graduating Volt- meter in terms of, 516 — i^of Clark's Cell, Temperature Variation of, 475 of Clark's Cell, Temperature Variution 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 DanieU's Cell, Method of Maintaining Constant, 427 of Daniell's Cell, Variation of, with Density of Solutions and Temperature, 426 of B.C.C. Cell, 460 of Edison-Lalande Cell, 464 of Oassner Dry Cell, 458 : of Grove's Cell, 440 of Grove's Cell Calculated from Chemical Action, 480 of Grove's Cell Diminishes with Use 441 of Hellesen Dry Cell, 459 of Leclanch^ Cell, and of Moditi- 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- periment to Show Fall of, when Current 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 Cunrent-Gienerator, Measuring when Variable, 369 of External Circuit, Receiving Maximum Power from Given Current-Generator, 893 Eneigy, Board of Trade Unit of, 349, 488, 491 Chemical, Apparatus for Trans- forming, into Electric Energy, 358, 859 Chemical, Conveited into Elec- tric Enenry 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, 880, 382, 383 Electric, Abstraction of, from Circuit by Current-Genera- tors, 871, 381 Electric, Apparatus for Con- verting into Other Nun-Heat Energy, 315, 371 Electric, Apparatus for Intro- ducing into Circuit, 358, 359 Electric Comparative Cost of Producing with Galvanic Cells and with Dynamo, 482- 491 Electric, Heat, and Mechanical, Conversion of, 314 -. Given to Circuit, 334-349 Electric, Measuring Heat Equi- valent of, 319 Electric, Meter. (See Joule- meter.) Electric, Rate at which Given to, or Taken from External Circuit by Current Genera- tor, 358, 371, 380-383 Electric, Bate at which Chemi- cal Energy is Converted into, in Cell, 361, 880, 382, 383 Electric, Rate at which Con- veited into Heat in Cell, 318, 370, 380-884 Electric, Rate of Conversion of, into other Non-Heat Energy, 370, 371 Electric, Transmission of, 352 "-— Electric, Transmission of, Model lUustratiug 855, 357 620 BNB PBAOTICAL ELECTRICITY. EXA r t Energy, Electric, Unit of, 817, 849 Heat, Production of, in Trans- formation of Energy, 404, 411 Heat, Bate of Conversion of Electric Energy into, 818- 824, 870, 880-884 — — Mechanical, Conversion of Energy of Current into, 814 Transmission of, Methods of, 862,854,856,867 Equilibiiom of Galvanometer Needle, Conditions of, 82, 111 Erg, Definition of, Note, 817 Meter, 834 Ergs par Second, Value of Watt in, 826 Value of Joule and Board of Trade Unit in, 817, 849 Evershed Gravity Control Ammeter, Latest Form, 142 Gravity Control Ammeter, Scale of, 144 Examples on E.M.F. of Batteries, Ixzxi-lxxxvii ; 867-868 on Consumption of Materials in Daniell's Cells, cxiii-cxvii ; 4S(M87 on Grove's Cells, cxviil-cxxiv ; 442-443 on Consumption of Materials in Ledanch^ Cells, cxxxi- cxxxv; 466-457 on Consumption of Materials in Potassium Bichromate Cells, cxxv-cxxx; 448-449 — - on Maximum Current through Cell, Cell not Abstracting Energy fi*om Circuit, zcvi; 886 on Measuring Besistances of Cells, cxxxvi-cxli ; 501-602 on An'angements of Colls, dxv- clxix ; 642-644 on Arrangements of Cells to Send Maximum Current through Given External Be- slstance, clxx-clxxiii ; 648- 649 on Safe Arrangement of Cells, clxxx-clxxxiii ; 561-562 • on Least Number of Cells for Given Curi'ent and P.D., clxxiv-clxxv ; 662^658 on Least Number of Cells to Give Fixed Power to Given External Circuit, clxxvi, dxxvii ; 554-556 ; dxxviii, dxxix ; 668-669 on Direction of Current, x-xii ; 87 on on on Examples on Currents in Parallel Conductors, llii ; 295 on Work done by Current, Ix-lxiii ; 81&-317 on E.M.F., and Bade B.M.F., of Generators and Motors, Ixxxviii-xcv ; 872-874 on Comparing B.M.Fs. of Generators, cxlii-cxlviii ; 605-607 on Efficiendes of Generators and Motors, civHsix ; 406-408 on Effideney of Electric Trans- mission of Energy, cx-cxii: 416-417 on Electrolysis, i-ix; 29-31 on Glow Lami» in Parallel and Tel^^ph Lines in Parallel, dii-clxiv ; 628-585 on Heat Equivalent of Electric Energy, Ixiv, Ixv ; 824 Clock Joulemeter, Ixxiv, Ixzv; 860 Cost of Electric Lighting, Ixxvi-lxxx ; 861-852 Potential, Quantity, and Density, 226-281 on Electric Power, Ixvi-lxx ; 827 -328 on Maximum Power Beceived by Whole, or Part, of External Circuit, xcvii-c ; 896-397 on Way in which Power Beceived by Whole, or Part, of Ex- ternal Circuit Varies from Maximum, d-ciii ; 4C3-4C4 on Units of P.D. GAL 621 Experiments, Graphically Recording Besults of, 60-62 Importance of Changing only One Variable at Once in, 254 External Circuit. {See Circuit, External.) F Farad, Definition of, 579 Faraday, Experiments on Electro- lysis by, 27 Experiments on Induction by, 213 Fault Testing in Telegraph Lines by Bright, Siemens, and Varley, 569 Feeders, Definition of, 526 Fibre and Pivot Saspensions, of Gal- vanometer Needle, 110 Field of Thomson Joulemeter, 345 Coils of Thomson Joulemeter, 845 Controlling. (See Controlling Field.) Deflecting. (See Deflecting Field.! Magnetic. (See Magnetic Field.) Mapping out of. (See Mapping out Field.) of Motor, Definition of, 842 Uniform Magnetic. (iSee Uni- form Magnetic Field.) Filings for Magnetic Lines of Force Diagrams, Preparation of, 665 Mapping out Lines of Force vith, 71-75, 77 Fletcher, Ohm Determined by, 688 Flow of Water, Connection between Rate 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, 826 Pounds. Value of Board of Trade Unit, Joule, and Erg in, 817, 849 Force between Coils of Clock Joule- meter Compared with Grav- ity, 886 •~— between Conductor and Magnet, Action of, 8, 120 •—— Controlling. (See Controlling Force.) Deflecting. (See Deflecting Force.) Force of Detadiment in Magnetic Experiments Aflbcted by Character of Surfaces, 66 Electromotive. (See E.M.F.) Exerted and Position of Coll in Weston Milammeter, 147 Exerted by Magnets, 63 Exerted on Electric Conductor by Magnet, Employment of, 180 Gauss's Absolute Unit of, 571 Lines of. (See Lines of Force.) in Magnif^^ng Spring Ammeter, Variation of, with Posi- tions of Iron Core and Coll, 187 None Inside Closed Conductor Due to Exterior Electro- static Action, 196 Produced in Closed Hollow Con- ductor by Current Flowing along, 197 Resultant, of Two Forces, Method of Obtaiuine, 81 Forces in Galvanometer, Method of ComiK)undlng, 80 Foster's Method of Subdividing Wire into Lengths having Equal Resistances, 518 Foucanlt Currents, Meaning of, 147 Fuses, Definition of, 182 Galvanic Cells. OAL Galvanometer, CalibratinSt on Sine Principle, Necessity for Cur- rent Kemaining Constant while, 124 Calibrating, on Sine Principle wben Needle Pivoted or Suspended, 120-123 Calibration of. Absolute and Relative, Meaning of, 40 Calibration Curve of, 62 Compounding Forces in, 80 Construction of, having Angu- lar Deflection Directly Pro- portional to Current, 124 Controlling Field on Needle having Very Small Deflec- tions, 126 Controlling and Deflecting Fields on Needle, When Uniform, 80, 81, 126 Controlling and Deflecting Forces on Needle of, 70, 81, 102, 111 d'Arsonval, Hodiflcations of, 144-161 d'Arsonval, Principle of, 130 Definition of, NoU, 43 Deflecting Force on Needle, Directly Proportional to Current, VO, 137, 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, 46, 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, 312 Differential, Obtaining Equality of Magnetic Effects, and Equality of Resistance of Wire of Coils, 240 Differential, Use of Shunts with, 811 Direct Reading, Definition of, 127 High Resistance, Why Used for P.D. Measurements, 178 Law of, 44, 69 Mather and Walmsley Projwr- tional, 125 Moving Coil, 129. (See al90 Ammeter, Moving Coil.) Needle, Conditions of Equi- librium of, 82, 111 Galvanometer Needle and Deflecting Force, Methods of Keeping Angle between Constant, 113 Needle, Why Given Deflection of. Occurs for Given Current, 09 Needle, Pivot, and Fibre Sus- pensions of, 110 P.Ds. Measured with, 176 for P.D. Measurements, Best Form of, 178 Proportional, of Mather and Walmslev, 125 Proportional, Types of, 124, 147 and Resistance, Measuring P.Dt*. with, 176 and Resistances, Comparing E.M.F8. of Cells 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 Seale 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, 566 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, Coil of. Adjusting, 85. Tangent, Coil Giving Gi'eatest Sensibility, 100 Tangent, Coil of. Why Circular, 107 Tangent, Coil of, Why Large, 99 Tangent, Constant for a.i>. 1891-1900,104 Tangent, Total Controllin;{ Force on Needle, 104 Tangent, Deflection in Ami)erea when Controlled only by Earth's Magnetism, 103 GAL INDEX. GOL 623 Galvanometer, Tangent, Deflection Best Used with, 90 Tangent, Deflection and Current Connection between, 88 Tangent, Detailed Description of, 49 , Tangent, Disadvantages of, 108 Tangent, with Needle Stiongly Magnetised, Advantages of, 91 Tangent, Scale for, 87 Tangent, Sensibility of, Experi- ment Showing Law and vari- ation, 100 Tangent, Sensibility of, Inde- gendent of Length and ti-ength of Needle, 91 ^— Tangent, Sensibility of. In- versely Pronortioual to Dia- meter of Cou, 98 Tangent, Sensibility of. Method of Increasing, 91, 98 Tangent, Sensibility Prooor- tional to Number of Con- volutions of Wire, 98 Tangent, Sensibility of. Re- strictions in Inci'easing, 98 Tangent, Sensibility of. Varies with Strength of Controlling Field, 102 Galvanometers and Ammeters, How Straight Line Law Obtain- able In, 125, 182, 187, 147 Joint Relative Calibration of, 288 of Invariable Sensibility, 127 Proportional, 124 and Voltameters, Relative Ad- vantages of, 42 Galvano.occ^, Definition of. Note, 43 Deflection of. Not Proportional to Current Strength, 22 Description of, 10 and Resistances, Comparing KM.Fs. of Cells with, 602-510 Gas, Current of, Measuring Distri- bution of Pressure in, 158 Pressure Compared with Elec- tric Potential, 204, 206-209, 231 Pressure, Variation of, with Mass, Temperature, and Volume, 204-208 Transmission of Energy by, 350 Weights of, and Charges of Electricity, 212 Volume of. Liberated per Second per Ampere, in Sulphuric Acid Voltameter, 29 Gassner's Di-y Cell, 458 Gauss's Absolute Unit of Force, 571 Generator of Current (JSee Carrent- GeheratorO German-Silver, ComiK>sition and Specific Resistance of, 267 Raising Specific Resistance and Lowering Temperature Go- efiicient of, 268 Resistance of, per Centimetre Cube and per Inch Cube, 259, 268, 271 Resistance of, per Foot Grain and per Metre Gramme, 261 Resistance, Percentage Varia- tion of, per I'C, 266, 267, 271 — : — Temperature Coefficient of Re- sistance of, 267, 268 Wire, Use of, in Resistance Coils, 280 Glazebrook, Notes to Specification of Clark Cell by, 470, 692 Ohm Determined by, 582 Glow Lamp, Efficiency of, 405 Percentage Variation of Light with Alteration of Current, 801 Variation of Light of, with Current and Pi'cssure, 490 Glow Lamps, Arrangement of Circuit to Give Fixed Amount of Power to, with Minimum Number of Cells, 556 In Parallel with House Mains, 800 Resistance of. INS \ Gold-leaf Electroscope, Testing Sisn of Charge and Potential wito, 219 •^— Electroscope, When Used, 193 — for Electroscope, Weight and Price of, 194 Gold-Silver Alloy, Reflistanoe of, per Centimetre Cabe, and per Inch Cabe, 259 •^— AU^, Resistance of, per Foot Grain and per Metre Gramme, 261 Alloy, Resistance of, Percentage Variation per 1*C., 266 Graduating Voltmeter by Potentio- meter Method with Clark's Cell, 516 Graphically Recording Results of Experiments, 50-62 — — Recording Results of Experiment for Calibrating Galvanometer, 51 Recording Resnlts of Experi- ments. Value 0^ 55 Gravity Control Ammeter. (See Ammeter. Gravity Control.) DanieU's Cells, 481-48a Deflectional Wattmeter, 832 Gray's Investigations on Electro- chemical Equivalents of Copper. 28 Grove's Cell. (See Cell, Grove's.) Gutta-Percha, Resistance of, per Centimetre Cube, 268 — Variation in Resistance of, with Temperature. 268 Heat of Combustion, Measurement of, 478, 481 and Electric Conductivities, Comparison of, 275 Equivalent of Electric Energy, Measuring, 819-824 — — Insulators for. Inferior to Those for Electricity, 276 Produced by Current^ 5, 9, 314 Produced in Transformation of Energy. 404 Rate at which Electric Energy in Circuit or Cell Converted into, 818, 870, 880-^4 Rate of Production of, by Current, Measuring, 819-394 Unit of, 818 Heating Property of Current Un- suitable for Measuring Cur- rent, 9, 12, 19 Heating Property of Oarrent, Uses 0^9 Hellesen Dry Cell, 458 Helmholtz, Alteratton In Definition of Ohm Suggested by, 589 Henry, Definition 0^591 Hermetically Sealed, Definilion of, NoU,42 High. Resistance Galvanometer, Wliy Used for P.D. Measurements, 178 Resistance Voltmeter, When Used, 181 Higher Potential of Conductor:, Defini- tion of, 162 Himstedt, Ohm Determined by, 588 Hoffmann's Sulphuric Acid Volta- meter, 82 Horizontal Component of the Earth's Magnetic Force, Meaning of, Note, 108 Horse-Power: Definition of, 827 Power, value of Watt in, 827 Power Hours. Value of Board of Trade Unit in, 849 Shoe Magnets, Lines of Force with, 74 Hydrogen. Combinalaon of, with Platinum in Smee's Cell, 423, 482 Deposition of. on Copper Plate of Cell, Effect of, 420, 462 Direction of Movement of, in Cells, 423 How to Prevent Combination of, with Negative Plate in Cell, 428 — Liberated per Second per Ampere In Sulphuric Acid Voltameter, 83 Liberation of, in Simple Voltaic Element, 418, 420 and Oxygen, Proportions of. 