None
APP 603 Needle, and Current, Rela- tion between, 82, 83 Anode, Definition of, 24, 33 for Silver Voltameter, Descrip- tion of, 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(51 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.O. be- tween Terminals, Resistance, and Current, 366 for Proving E.M.F. of Cell Independent of Positions and Sizes of Plates, 363 for Experiments on Polarisation of Cell, 422 for Altering the Arrangements of a Group of Cells, 539-542 for Proving No Electrostatic Force Inside Closed Con- ductor, 196, 216 for Proving that No Electricity at Rest Inside a Conductor, 210, 216 for Showing that Conductor Carrying Current is Moved by Magnet, 3, 4 for Showing that Current De- composes Liquid, 4, 7 for Showing that Current Deflects Magnet, 3 for Showing that Current Heats Conductor, 5, 8 for Showing that Current Mag- netises Iron, 3, 5 — for Showing Mutual Action of Two Wires Carrying Currents, 3, 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 E.M.Fs., 508 for Converting Electric Energy into Non-Heat Energy, 371 for Introducing Electric Energy into Circuit, 358 Apparatus for Measuring Heat Equi- valent of Electric Energy, 320, 321 for Measuring Energy, 313-324, 334-348 Illustrating Electric Transmis- sion of Energy, 355, 357 for Calibrating Galvanometer by Using Known Resistances, 521 for Calibrating Galvanometer by Sine Method, 120 for Calibrating Any Galvano- meter by Comparison with Tangent Galvanometer, 109 for Calibrating Galvanometer by Comparison with Voltameter. 46 for Mapping Out Lines of Force Due to Coils, 71, 76, 100, 565 for Mapping Out Lines of Force Due to Magnets, 72-75, 565 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. (See Meas- uring P.D.) for Proving that Potential of Conductor Varies with Posi- tion, Charge, Size and Shape, 202-208, 216 for Testing Distribution of Potential along Wire Convey- ing Current, 255 — for Showing Difference Between Potential, Quantity, and Density, 226-231 for Illustrating Analogies be- tween Gas Pressure and Elec- tric Potential, 158, 159, 203- 207 for Testing Distribution of "Water Pressure, 154, 157 for Comparing Quantities of Electricity, 215-217 for Measuring Power, 329-333 Used as Adjustable Resistance for Large Currents, 270 for Measuring Temperature Variation of Resistance, 202, 263 for Measuring Variation of Re- sistance with Length, Cross- Section, and Material, 254-257 604 APP PRACTICAL ELECTRICITY. BAT Apparatus Employed by B.A. Com- mittee for Determining Unit of Resistance. 572 for Testing Resistance of Branch Circuits in Parallel, 294 for Comparing and Measuring Resistances. (Scr, Comparing Resistances, and Measuring Resistance.) for Testing Sine Law, 113-117 Testing Sign of Charge and Potential, 219-222 for Testing Tangent Law, 92, 93 for Calibrating Deflectional Volt- meter, 183-187 for Graduating a Voltmeter with Clark's Cell, 516 for Testing Voltmeter, 511 Arc, Difficulty of Determining Back E.M.P. of, 372 Meaning of Apparent Resistance of, 233 Measuring Apparent Resistance of, 233 Armature of Motor, Definition of, 342 of Thomson Joulemeter, 343 of Thomson Joulemeter, Cause of Rotation of, 345 of Thomson Joulemeter, Direc- tions of Currents in, 344 • of Thomson Joulemeter, How Motion of, is Impeded, 346 of Thomson Joulemeter, Mag- netic Field Produced by, 345 of Thomson Joulemeter, Rota- tion cf, Proportional to Energy Supplied, 347 Arms of Wheatstone's Bridge, Ad- justment of, to Obtain Greatest Sensibility, 285 of Wheatstone's Bridge, Law Connecting Resistances of, 243 of Wheatstone's Bridge, Prac- tical Limitation to Inequality of, 284 of Wheatstone's Bridge, Resist- ance of One in Terms of Re- sistances of the Others, 245 Aron Supply Meter, 339-341 Supply Meter, Differential Gear- ing for, 340 Arrangement of Group of Cells, Method of Altering, 539 Arrangements of Cells, 530 Atomic Weights of Copper, Silver, and Zinc, 27 Axis, Magnetic, Definition of, 67 Aylmer-Leclanche Cell, 455 Ayrton and Mather's Moving Coil Ammeter, 148 Ayrton and Mather's Non-inductive Resistance Coil for Large Currents, 282 and Mather's Universal Shunt, 303 and Mather's Universal Shunt Box, 304-310 • and Mather's Zero Electrostatic Voltmeter, 164, 179 Ayrton and Perry's Gold-leaf Electro- scope, 192 and Perry's Joulemeter, Original Gaining Clock Form, 334 and Perry's Magnifying Spring, 64 and Perry's Magnifying Spring Ammeter, 135-138 and Perry's Ohmmeter, 233 and Perry's Permanent Magnet Ammeter, Various Forms of, 130, 132, 133 Ayrton's Moving Coil Ammeter with Magnetic Control, 150 Back E.M.F. (See E.M.F., Back.) Balance, Wheatstone's. (See Bridge, Wheatstone's.) with Wheatstone's Bridge, Definition of, 245 Bar Magnet, Apparatus for Measuring Distribution of Magnetism in, 63 Magnet, Lines of Force with, 72, Batteries, Mercury Switch-board for, 539-542 with Different Arrangements of Cells, E.M.Fs. BRI 605 Battery, E.M.F. of, P.D. between Terminals, Resistance, and Current, 364, 380 Back E.M.F. of, Method of Measuring, 371 Muirhead's Telegraph, 435 P.D. between Terminals of, when Maximum Power Gi von to External Circuit, 389, 548 Potential in, Diagrams Show- ing Distribution of, 374-381, 384 Power Developed by, and Num- ber of Cells, 360 Prices of Materials Consumed in, 485 Produces Constant P.D. round Entire Circuit, 361 - — - Ratio of Power Developed by, to Current, 370 Resistance of, Measuring when Not Very Small, 493 Resistance of, Measuring when Very Small, 492 Resistance of, Measuring with Ammeter and Voltmeter, 366, 492 Single, Used for Working Several Telegraph Wires, 527, 528 Symbolical Representation of, 237 When Necessary to Join all Cells of, in Series, 552 B.A. Unit, Aim in Choosing, 576 Unit, Definition of, 573 Unit, First Indication of Value being Too Small, 576 Unit, Rayleigh's Value of, in C.G.S. CAR Bridge, Wheatstone's, Balance with, Definition of, 245 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, Proofs 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 Wlieatstone'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, 283 Wire, Material for, 247 • Wire, Advantage of Using Long, 249 Bright, Sir Charles, Proposes Names Ohniad and Volt, 573, 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 Brushes of Elihu Thomson Joule- meter, 343 Bunsen's Cell. (See Cell, Bunsen's.) Burnley Dry Cell, 459. (See also Cell, B.C. 0. Dry.) Calibrating Ammeter with Silver Voltameter, 25, 596 Galvanometer by Comparison with Tangent Galvanometer. 108 Calibrating Galvanometer by Com- parison with Voltameter, 46 Galvanometer by Sine 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, 332 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, Joint Relative of Two Galvano- meters, 238 Relative, of Galvanometer, Definition of, 45 Straight Line Law, How Ob- tainable in Ammeters and Galvanometers, 125, 132, 137, 147 Oallaud Cell, 432 Callendar, Experiments on Tempera- ture Coefficient of Platinum, 265 Calorie, Definition of, 318 Power Required to Generate One, per Second, 479 Calories, Current, Resistance, and Time, Relation between, 318, 324 Calorimeter, 12, 18, 320 Capacity, Electric, Unit of, 579 Carbon, Utilising Negative Tempera- ture Coefficient of, 268 Percentage Temperature Varia- tion of, 271 — Plate, Cylinder, and Rod of Cells, 443, 445, 450, 452, 458, 460, 461 Resistance of, per Centimetre Cube, 267, 271 CAE INDEX. GEL 607 Carbons for Bunsen's Cell, Manufac- ture of, 444 Carpentier's Proportional Galvano- meter, Principle of, 125 Case, Conducting. (See Conducting Case.) Cathode, Definition of, 24, 33 for Silver Voltameter, Descrip- tion of, 23, 26 Weights of Metals Deposited on, 27 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 Leclanche, 455 Bunsen's, 443 Bunsen's, Compared with Grove's Cell, 443 Bunsen's, E.M.F. of, 444 Burnley Dry, 459. (See also Cell, E.C.C. Dry.) Callaud, 432 Chemical Action in, E.M.F. Calculated from, 477-482 Chemical Actions in Different Types of, 418, 424, 427, 438, 439, 445, 450, 463, 478 Chromic Acid, 445-448 Chromic Acid, Weights and Cost of Materials Consumed in, per Board of Trade Unit Pro- duced, 487 Chromic Acid, Weights of Materials Consumed in, inn- Hour per 1,000 Amperes, is I Clark's, 466-477, 516-521, 588, 589, 590, 594, 597-599 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 Kahle's H Form of, 474 Clark's, Definition of, 467, 597 Clark's, Effect on E.M.F. of Sending too Large a Current, 477 Clark's, E.M.F. of, 467, 470, 474, 588, 589, 594 Clark's, E.M.F. of, Temperature Variation of, 475 Clark's, E.M.F. of, Temperature Variation of, Affected 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, Kahle's Modification of Rayleigh's H Form of, 472 Clark's, P.D. between Terminals of, 589, 594 Clark's, Potentiometer Method of Graduating Voltmeter with, 516-519 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, Resistance Advisable for Use with, 477, 511 Clark's, with Fixed Resistance as Standard of Current, 519 Copper - Zinc-Dilute - Sulphuric - Acid. (See Simple Voltaic Element.) Daniell's, 423-436, 451, 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 Leclanche Cell, 451 Daniell's, Copper Deposited per Hour per Ampere, 424 Daniell's, Copper Sulphate Con- sumed per Hour per Ampere, 425 Dauiell's Depolariser of, 423 Daniell's, E.M.F. of, Calculated from Chemical Action, 478 Daniell's, E.M.F. of, Method of Maintaining Constant, 427 Daniell's, E.M.F. of, Values of, 426, 478, 539 Daniell's, E.M.F., Variation of, with Density of Solutions and Temperature, 426 Daniell's, Forms of, 431. (See also Cell, Callaud, Gravity, Meidinger, Minotto.) Daniell's, Local Actions in, 429, 430 Daniell's, Precautions in Con- struction of, 420, 428, 430, 431 608 CEL PRACTICAL ELECTRICITY. CEL Cell, Daniell's, Precautions when Us- ing, 425, 427, 435 Daniell's, Prevention of Copper Sulphate Diffusing through Porous Partition of, 430 Daniell's, Prevention of Forma- tion of Cupric Oxide in, 430 Daniell's, Resistance Varies with Constancy and Portability, 431 Daniell's, Resistance of, Varies with Temperature, 436 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 Darnell'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 Depolariser First Used in, 423 • — - E.C.C. Dry, 459 E.C.C. Dry, Compared with Hellesen Cell, 430 E.C.C. Dry, E.M.F. of, 460 Edison- Lalande, 462-465 Edison-Lalande, Chemical Ac- tion in, 463 Edison-Lalande, Depolariser of, 462 Edisou-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, 521 E.M.F. of, Calculated from Chemical Action in, 477-482 E.M.F. of, Compared with E.M.F. of Standard Cell, 502-510 E.M.F. of, Determined, with Voltmeter, 362, 365 with E.M.F. Helping Current May Abstract Energy from Circuit. 382 Cell, E.M.F. of, P.O. between Ter- minals, Resistance, and Cur- rent, 364, 3SO E.M.F. of, When Equal to Ter- minal P.O., 522 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 from Circuit, 371, 383 Gassner Dry, 458 Gassner Dry, Commercial Im- practicability of, 458 Gassner Dry, E.M.F. of, 458 Gravity Daniell's, 431-433, 436 Gravity Daniell's, Precautions when Using, 432, 436 Grove's, 438-442, 480, 484, 486, 527, 550-552 Grove's, Chemical Action in, 438, 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.M.F. CEL 609 Cell, Lalande-Chaperon, 462 Lalande-Chaperon, Defects of, 463 Leclanche, 449-456, 484, 487 Leclanche, 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 Leclanche, When Used, 451 Leclanche Agglomerate, 452 Leclanche Agglomerate, Forma- tion of the Agglomerate, 452 Leclanche-Aylmer, 455 Leclanche-Barbier, 452-455 Leclanche-Barbier, Advantages of, 454 Leclanche-Barbier, Composition of Salt Used in, 454 Leclanche, Chemical Action in, 450 Leclanchd, Compared with Darnell's Cell, 451 Leclanche, Depolariser of, 450 Leclanche, Disadvantages of, 452 Leclanche, E.M.F. of, 451 Leclanche, Modifications of, 452-456 Leclanche, Precautions in Con- struction of, 451 Local Action, How Caused in, 429, 430 Marie-Davy Mercuric Sulphate, Unsuitability of, for Practi- cal Use, 477 Meidinger, 431 Minotto's, 433 Obach Dry, 460 Obach Dry, E.M.F. of, 462 P.D. between Terminals of, Constant, when Low Internal Resistance, 522 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, 376 Potassium Bichromate, 445-448, 484, 487 Potassium Bichromate, Chemi- cal Action in, 445 Potassium Bichromate, E.M.F. of, 446 - — Potassium Bichromate, Precau- tions when Using, 445, 447 U Cell, Potassium Bichromate, 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, 384 Potential in, Uncertainty as to Method of Variation of, 374 Potentials of Terminals of, Relatively to Earth, 375 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 from, Outside Circuit by, 316, 380, 382, 383 Rate at which Electric Energy is Converted into Heat in, 370, 380-384 Resistance of, Choice of Method for Measuring, 408 Resistance of, Conditions Gov- erning, 434 Resistance of, Measuring when Not Very Small, 493 Resistance of, Measuring when Very Small, 366, 492 Safety Limitation of Maximum Current for, 559 Secondary. (See Accumulator.) Short-Circuiting, 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, 376 Cells Abstracting Energy from Out- side Circuit, Diagram Show- ing, 384, 385 — Arrangements of, 536 Arrangement of Circuit 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, 4G1 610 CEL PRACTICAL ELECTRICITY. CHR Cells, Commercial Value of Waste Products of, 438, 490 — Conditions for Commercial Use of, for Electric Lighting, 491 Copper Oxide Plate of, 462, 463 Copper Plate of, 419, 422, 431, 433, 435 Cost of Producing Board of Trade Unit with, 482, 488 Coupling with Mercury Switch- board, Methods of, 541 Distribution of Potential in, 874-380 Dry, 457-462 Dry, Advantages of, 457, 458 Dry, Early Attempts at Con- struction of, 457 and Dynamo, Comparative Cost of Producing Electric Energy with, 482-491 E.M.FS. of, Comparing, 502-510 Joined in Parallel, Series, and Parallel Series, 536-537 Joined in Parallel, E.M.F. of Battery Formed of, 538 Joined in Series, Curve Connect- ing Number of, and Current, 546 Joined in Series, E.M.F. of Battery Formed of, 537 Leclanche, Leclanche-Barbier, and Aylmer-Leclanche, Com- parison 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, 423, 431, 433, 435, 438, 443, 445, 450, 452, 453, 455, 460, 461, 462 Number of, in Series and Rate of Chemical Action, 360 — - Platinum Plate of, 423, 438, 482 Polarising Rapidly, Measuring Resistance of, 498 Positive or Zinc Plate of, 419, 423, 431, 433, 435, 438, 445, 450, 454, 455, 458, 459, 460, 461, 462, 463 Potential Lost in, Graphical Representation of, 379 — Prices of Materials Consumed 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, 488-491 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, 573, 576, 578, 579, 583, 587, 593 Charge, 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. ) Chromium Trioxide Consumed in Cell per Board of Trade Unit Pro- duced, 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 Circuit, Abstraction of Energy from, by Generators, 371, 881 Arrangement of, Requiring Least Number of Cells to give Fixed Power to External Portion, 555 Back E.M.F. in, 370 Complete Electric, Description of, 352 Distribution of Potential in, 376 Distribution of Potential in, with E.M.F. Opposing, 378 Electric, Analogies with, 354, Electric, Mechanical Model Illustrating, 355-357 External, Arrangement of Bat- tery to Give Maximum Cur- rent and Power to, 545 External, Arrangement of Part of, to Receive Maximum Power, 393 External, Conditions Governing Variation of Potential along, 374, 375 External, E.M.F. of, to Receive Maximum Power from Given Current Generator, 393 External, Rate at which Energy Given to, or Taken from, by Generator, 358, 371, 380-383 External, Receiving Maximum Power from Given Generator, 385-393 External, with Opposing E.M.F., Distribution of Potential in, 378 External, Variation of Received Power from Maximum, 397 Introducing Electric Energy into, 358 Maintaining P.O. between Ends of, Constant, 287 Part of, in which Potential Diminishes in Direction of Current, 352 Part of, in which Potential Increases in Direction of Current, 353 Circuit, Power Absorbed in, Exterior to Generator, 370 Raising Potential of Electricity in, 353 Rate of Introduction of Electric Energy into, 358 Rate of Production of Heat in, 318-327 Single, Definition of, 377 Single, Uniformity of Current in, 377 Circuits, Parallel, Independence of Currents in, 525 Clark's Cell. (See Cell, Clark's.) Clark, Latimer, Proposes Names Ohmad and Volt, 573, 576 Clock Joulemeter. CON Coils for Differential Galvanometer, Construction of, 240 for Differential Galvanometer, Equality of Magnetic Effects and Equality of Resistance, 240 of Motor, 342 of Ohmmeter, 233 of One B.A. Unit of Resistance, Verification of, 574 for PortableWheatstone's Bridge, Values of, 287 of Proportional Galvanometer, 125 for Resistance Boxes, Values of, 283 of Shunt Box, 295, 297 of Thomson Joulemeter, 341-345 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, 280-283 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 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, 331 Commutator, Description of, 342 of Elihu Thomson Joulemeter, 343, 348 Comparing E.M.Fs. of Cells, 502-510 (See also Measuring E.M.F.) P.Ds. by Current Method, 176 (See also Measuring P.D.) Quantities of Electricity, 211 Resistances in Parallel by Differential Galvanometer, 238 Resistances in Parallel by Wheat- stone's Bridge, 241-253 Resistances in Series, 177, 184, 186 Resistances by Simple Substitu- tion, 235 Comparing Resistances. CUP 613 Conductor with Current Passing nnd Magnet, Force Exerted Be- tween, 3, 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 Rest 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, 207 With Negative Temperature Change of Resistance, •_'(>:, 269, 271, 312 - — - With No Temperature Change of Resistance, 269 With Small Temperature Change of Resistance, 266-271 Constant and Uniform, Difference between, Note, 153 E.M.F., 522 for Tangent Galvanometer, A.D. 1891-1900, 104 P.D., 522 Construction of Galvanometer Scale Giving Relative Current Strengths, 58 Construction of Galvanometers with Angular Deflection 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 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, 10:5 Force, Total, on Tangent Gal- vanometer, Determination of, 104 Cooper's Modification of Kahle's H Form 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, 431, 433, 435. (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, Note, 312 Temperature Coefficient of, 265, 266 Oxide Consumed in Edison- Lalande Cell per Board of Trade Unit Produced, Weight and Cost of, 465, 487 614 COP PRACTICAL ELECTRICITY. CUR Copper Oxide Consumed 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, Weight and Cost of, 486 Sulphate Consumed in Daniell's Cell per Hour per 1,000 Amperes, 425, 484 Sulphate, Diffusion of, in Daniell's Cell, 430 Sulphate, Heat Absorbed in Decomposition of, 478 Voltameter, 10 — Voltameter, When Used, 26 Cost and Weights of Materials Con- sumed in Cells per Board of Trade Unit Produced, 486, 487 Comparative, of Using Cells and 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, 348 Crompton 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, 328 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, 397 Choice of Method for Measuring, 9-14 Decomposition of Liquid by, 4,10 Deflection of Magnet by, 3, 5, 34, 69 Direction of, in Cells, 423, 424, 427, 438, 439, 445, 446, 450, 463 Direction of Flow, Definition of, 2, 31 Current, Direction of, How Deter- mined, 34, 134 Direction of, and Magnetic Polarity, Connection be- tween, 36 Direction of, When Necessary to Know, 134 Density, Definition of, 483 Electric, Compared with Cur- rent of Water, 2, 5, 13, 152, 313, 353, 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 E.M.F. Helping May Abstract Energy, 381 -Generator, E.M.F. of, and Loss of Power in Electric Trans- mission, 410 Generator, E.M.F. of, Definition of, 369 Generator, External Circuit Re- ceiving Maximum Power from, 385-395 Generator, Finding Circuit Re- ceiving Maximum Power from, 391 Generator, Measuring E.M.F. of, 369 — - -Generator of Fixed E.M.F. of, 370 Generator with Variable E.M.F., 369 Generator, Work done by, 157,359 — 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, 364 in Battery, Proportional to Chem- ical Action, 359 in Cell in Terms of P.D., E.M.F., and Resistance, 3(54, 380-383 in Circuit, P.D. between Ter- minals, and Power, 370 CUR INDEX, CUR 615 Current in Circuit, Uniform Strength of, 152, 377 in Daniell's Cell, Variation of, •with Temperature, 436 in Galvanometer and Deflection of Needle, 45, 84, 112, 124, 127 in Galvanometer and Force Keeping Needle at Rest, 70 in Tangent Galvanometer with Earth's Control, Formula Giving, 103 in Generator, Ratio of, to Power Developed, 370 in Magnifying Spring Ammeter Proportional to Angular De- flection, 137 in Simple Voltaic Element, Cause of Diminution of, 421 in Voltameter, Direction of, 33 Magnetisation of Iron by, 3, 5, 35 Maximum, for Cell, Safety Limitation of, 559 Maximum, through Given Ex- ternal Resistance, Arrange- ment of Given Number of Cells to Produce, 545 Measured by Chemical Property, 14-23 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, Electromagnet, Galvano- meter, Galvanoscope, Volta- meter.) Measuring Rate of Heat Pro- duced by, 319 Measuring, Standard Resistance Used in, 520 Measuring. (See also Measuring Current.) Method of Comparing P.Ds., 176 P.O. to Send, round Entire Circuit Constant for Given Battery, 361 Power, and P.D., Relation be- tween, 327 Primary, Direction of, in Expe- rimental Voltaic Element, 423 Current, Production of, 15C. (See also Battery, Cell, and Current- Generator.) Production of, between Two Conductors, 161 Properties of, 3 Property of, Best to Measure Strength by, 20 Proportional to Rate of Chemical Action, 22, 361 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, 423 Strength, Definition of, 23 Unit of. (See Ampere.) Unit of, Aim of B.A. Commit- tee in Choosing, 576 Uses of Different Properties of, 9 Variation of Effect of Shunt on witli Change of External Resistance, 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 Maintained, 156 of Water and Loss of Head, 153-156 of Water, Work Done by, 313 Electric, Work Done by, 313 Voltmeter. (See Voltmeter.) Currents, Eddy or Foucault, 147 in Armature of Elihu Thomson Joulemeter, Directions of, 344 in Batteries with Different Ar- rangements of Cells, 537 in Elihu Thomson Joulemeter Proportional to Magnetic Fields Produced, 346 in Parallel Circuits, Independ- ence of, 525 • in Parallel Conductors, Ratio of, to Current in Main, 295 in Shunt and Galvanometer, Ratio between, 290 in Shunt and Galvanometer Ratio of each to Whole Current, 290J Local, 429 616 CUR PRACTICAL ELECTRICITY. DIF Currents Passing through Two Con- ductors in Parallel, Measure- ment of, 238 Through Two Conductors in Parallel Inversely Propor- tional to Resistances, 238 Curve, Calibration. (See Calibration Curve.) « Connecting Galvanometer De- flection and Current, 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 Character of Re- sult Obtained Shown by, 5<> Recording Results of Experi- ment for Calibrating Gal- vanometer, 52 Showing Current Giving Maxi- mum Power to External Circuit, 387 Curves, Choice of Abscissae, Ordinates and Units for, 57 Connecting Variation of Resist- ance of Metals with Temper- ature, 264, 265 Drawing, on Squared Paper, 51 How Drawing of, Corrects Re- sults of Experiments, 55 Results of Intermediate Untried Experiments Obtainable from, 55 Showing Tests on Three Types of Leclanche Cell, 456 Cylinder, Zinc Plates of Cells in Form of, 431, 455, 461 Daniell's Cell. (See Cell, Daniell's.) Use of Depolariser, 4:23 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, 134, 147, 149 Decomposition of Liquid by Electric Current, 4, 12, 20, 359 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 Needl?. ELB 617 Differential Galvanometer, 238. (See also Galvanometer, Differen- tial.) Gearing of Supply Meter, 340 Direct Reading Galvanometer, Defini- tion of, 127 Reading Electrostatic Voltmeter, Construction of Scale for, ISO Direction of Current, Meaning and Definition of, 2, 31 of Current, How to Reverse without altering Value of, 87. of Current, when Necessary to Know, 134 of Current Shown with Per- manent Magnet, Magnifying Spring, and Moving Coil Am- meters, 134, 13(5, 145 Disconnecting Ammeter, Result of, 181, 183 Voltmeter, Result of, 181, 183 Dissimilar Magnetic Poles, Action between, 69 Distribution of Charge, 224 of Magnetism in Magnet, 03 of Potential in Battery, 374 Dorn, 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, Note, 317 E " Earth," Definition of, 162 • Potentials of Terminals of Cell Relatively to, 375 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 Earthing, Definition of, 162 Ebonite, Electrification of, 214 E.C.C. Dry Cell, 459. (See also Cell, E.C.C. Dry.) Eddy Currents, Meaning of, 147 U* 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. (See Conductivity.) Conductor. (See Conductor.) Current. (See Current.) Density. (See Density, Electric.) Energy. (See 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 Efficiency. (See Efficiency, Elec- trical.) Standards. (-See Standards, Elec- trical.) Units. (See Units, Electrical.) Electricity, Charge of. E.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 Gold-leaf Electro- scope, 221 Electrochemical Equivalents of Copper and Zinc, 27, 28 Electro-Dynamometer, Principle of, 575 Electrolysis, Faraday's Experiments on, 27 of Dilute Sulphuric Acid, 32, Note, 62 Electrolyte, Decomposed into Ions, Electrolytic Action Produced in Given Time by Given Cur- rent, Conditions Governing Amount of, 27, 483 Electromagnet, Description of, 10, 17 Electromagnetic System of Units, Absolute, 571. (See ulso Absolute Electromagnetic System.) Electrometer, Ayrton and Mather Zero, 164, 181. (See also Voltmeter, Zero Electro- static.) Zero Type of, 163 Electrometers, Types of, 162 Electromotive Force. (See E.M.F.) Electromotor and Thermo-pile, Use of, for Conversion of Energy, Note, 563 Series or Single Circuit, Defin- ition of, Note, 371 Electronegative and Electropositive Ions, Definition of, 33 Electroscope, Gold-leaf, 191-196, 219- 222 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-leaf, When Used, 191 Electroscopes 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 Element, Simple Voltaic. (See Simple Voltaic Element.) Elihu Thomson Joulemeter. (See Joulemeter, Thomson.) E.M.F. Back, Change of, and Varia- tion of Current, 372 Back, Definition of, 371 Back, of External Circuit Re- ceiving Maximum Power from Given Current-Genera- 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, 393 Back of Electric Arc, Difficulty of Determining, 372 Back, to Produce most Rapid Transformation of Energy, 393-395 Constant, 522 of Battery, Definition of, 361 • of Battery, Conditions Govern- ing, 361 of Battery, Definition of, 301 of Battery, Measuring, 305 of Battery, P.D. between Ter- minals, Resistance and Cur- rent, 364, 380-383 E.M.Fs. INDEX. ENE 619 E.M.F. of Cell Independent of Size and Shape of Plates, 362-364 of Cell, Measurement of, 362, 365, 477 of Cell, When Equal to Terminal P.D., 522 of Bunsen's Cell, 444 of Burnley Dry Cell, 460 of Clark's Cell, 467, 470, 474, 588, 589, 594 of Clark's Cell, Effect of Send- ing too Large a Current on, 477 • of Clark's Cell, Potentiometer Method of Graduating Volt- meter in terms of, 516 of Clark's Cell, Temperature Variation of, 475 of Clark's Cell, Temperature Variation of, Affected by Method of Construction, 475 of Dauiell's Cell, and of Modifi- cations, 426, 430, 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, with Density of Solutions and Temperature, 426 of E.C.C. Cell, 460 of Edison-Lalande Cell, 464 of Gassner 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 Leclanche Cell, arid 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- 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, 369 of Current-Generator, Increase of, with Power Transmitted for Same Efficiency, 410 of Current-Generator, Measuring when Variable, 369 of External Circuit, Receiving Maximum Power from Given Current-Generator, 393 Energy, Board of Trade Unit of. 349, 488, 491 Chemical, Apparatus for Trans- forming, into Electric Energy, 358, 359 Chemical, Conveited into Elec- tric Energy per Second per Ampere in Daniell's Cell, 478 Chemical, Conversion of Elec- tric Energy into, 315 Chemical, Rate at which Con- verted into Electric Energy in Cell, 361, 380, 382, 383 Electric, Abstraction of, from Circuit by Current-Genera- tors, 371, 381 Electric, Apparatus for Con- verting into Other Non-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 Electric, Conversion of Heat Energy into, with Thermo- pile, Note, 563 Electrical Efficiency of Trans- mission of, 409 Electrical Efficiency of Trans- mission, How to Make Large, 410 Electric, Liberated by Chemical Action in Cell, Calculation of E.M.F. from, 477 Electric, Measuring Amount of, 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, Rate at which Chemi- cal Energy is Converted into, in Cell, 361, 380, 382, 383 Electric, Rate at which Con- verted into Heat in Cell, 318, 370, 380-384 Electric, Rate of Conversion of, into other Non-Heat Energy, 370, 371 Electric, Transmission of, 352 Electric, Transmission of, Model Illustrating 355, 357 620 ENE PRACTICAL ELECTRICITY. EXA Energy, Electric, Unit of, 317, 349 Heat, Production of, in Trans- formation of Energy, 404, 411 Heat, Rate of Conversion of Electric Energy into, 318- 324, 370, 380-384 Mechanical, Conversion of Energy of Current into, 314 Transmission of, Methods of, 352, 354, 356, 357 Equilibrium of Galvanometer Needle, Conditions of, 82, 111 Erg, Definition of, Note, 317 Meter, 334 Ergs par Second, Value of Watt in, 326 Value of Joule and Board of Trade Unit in, 317, 349 Evershed Gravity Control Ammeter, Latest Form, 142 Gravity Control Ammeter, Scale of, 144 Examples on E.M.F. of Batteries, j Ixxxi-lxxxvii ; 307-368 on Consumption of Materials in Daniell's Cells, cxiii-cxvii ; j 436-437 on Grove's Cells, cxviii-cxxiv ; 442-443 on Consumption of Materials in Leelanch6 Cells, cxxxi- cxxxv ; 456-457 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 Measuring Resistances of Cells, cxxxvi-cxli ; 501-502 on Arrangements of Cells, clxv- clxix ; 542-544 on Arrangements of Cells to Send Maximum Current through Given External Re- sistance, clxx-clxxiii ; 548- 549 on Safe Arrangement of Cells, clxxx-clxxxiii ; 561-562 on Least Number of Cells for Given Current and P.D., clxxiv-clxxv ; 552-553 on Least Number of Cells to Give Fixed Power to Given External Circuit, clxxvi, clxxvii; 554-555; clxxviii, clxxix ; 558-559 on Direction of Current, x-xii ; 37 Examples on Currents in Parallel Conductors, liii ; 295 on Work done by Current, Ix-lxiii ; 316-317 on E.M.F., and Back E.M.F., of Generators and Motors, Ixxxviii-xcv ; 372-374 on Comparing E.M.Fs. of Generators, cxlii-cxlviii ; 505-507 on Efficiencies of Generators and Motors, civ-cix ; 400-408 on Efficiency of Electric Trans- mission of Energy, cx-cxii : 416-417 on Electrolysis, i-ix ; 29-31 on Glow Lamps in Parallel and Telegraph Lines in Parallel, clii-clxiv ; 528-535 on Heat Equivalent of Electric Energy, Ixiv, Ixv ; 324 on Clock Joulemeter, Ixxiv, Ixxv ; 350 on Cost of Electric Lighting, Ixxvi-lxxx ; 351-352 on Potential, Quantity, and Density, 226-231 on Electric Power, Ixvi-lxx ; 327 -328 on Maximum Power Received by Whole, or Part, of External Circuit, xcvii-c ; 396-397 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. GAL 621 Experiments, Graphically Recording Results of, 50-62 Importance of Changing only One Variable at Once in, 254 External Circuit. (See Circuit, External.) 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 Yarley, 569 Feeders, Definition of, 526 Fibre and Pivot Suspensions, of Gal- vanometer Needle, 110 Field of Thomson Joulcmeter, 345 Coils of Thomson Joulemeter, 345 Controlling. (See Controlling Field.) Deflecting. (See Deflecting Field.) Magnetic. (See Magnetic Field.) Mapping out of. (See Mapping out Field.) of Motor, Definition of, 342 Uniform Magnetic. (See Uni- form Magnetic Field. ) Filings for Magnetic Lines of Force Diagrams. Preparation of, 565 Mapping out Lines of Force with, 71-75, 77 Fletcher, Ohm Determined by, 583 Flow of Water, Connection between Rate of, and Loss of Head, 168 Fluid Pressure, Distribution of, Com- pared with Distribution of Potential along Conductor, 1(57 Foot Pounds per Second, Value of Watt in, 326 Pounds, Value of Board of Trade Unit, Joule, and Erg in, 317, 349 Force between Coils of Clock Joule- meter Compared with Grav- ity, 336 between Conductor and Magnet, Action of, 3, 129 Controlling. (See Controlling Force.) Deflecting. (See Deflecting Force.) Force of Detachment in Magnetic Experiments Affected by Character of Surfaces, 66 Electromotive. (See E.M.P.) 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, 571 Lines of. (See Lines of Force.) in Magnifying Spring Ammeter, Variation of, with Posi- tions of Iron Core and Coil, 137 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 Obtaining, 81 Forces in Galvanometer, Method of Compounding, 80 Foster's Method of Subdividing Wire into Lengths having Equal Resistances, 513 Foucault Currents, Meaning of, 147 Fuses, Definition of, 182 Galvanic Cells. GAL Galvanometer, Calibrating, on Sine Principle, Necessity for Cur- rent Remaining Constant while, 124 Calibrating, on Sine Principle when Needle Pivoted or Suspended, 120-123 — - Calibration of, Absolute and Relative, 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 Deflec- tions, 12G 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, 144-151 d'Arsonval, Principle of, 130 Definition of, Note, 43 Deflecting Force on Needle, Directly Proportional to Current, 70, 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, 45, 84, 112, 124, 127 Deflection of Needle, and Cur- rent, Methods of Producing Direct Proportionality Be- tween, 124 Differential, 238 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, 311 • Direct Reading, Definition of,127 High Resistance, Why Used for P.D. Measurements, 178 Law of, 44, 69 Mather and Walmsley Propor- tional, 125 Moving Coil, 129. (See also 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, 69 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 Walmsley, 125 Proportional, Types of, 124, 147 and Resistance, Measuring P.Ds. with, 176 and Resistances, Comparing E.M.Fs. 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 — 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, 566 Tangent, 83 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 Greatest Sensibility, 100 Tangent, Coil of, Why Circular, 107 Tangent, Coil of, Why I^rge, !>'.» Tangent, Constant for A.I>. 1891-1900, 104 Tangent, Total Control ling Force on Needle, 104 Tangent, Deflection in Amperes 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, S3 Tangent, Detailed Description of, 49 Tangent, Disadvantages of, 108 Tangent, with Needle Strongly Magnetised, Advantages of, 91 Tangent, Scale for, 87 Tangent, Sensibility of, Experi- ment Showing Law and Vari- ation, 100 Tangent, Sensibility of, Inde- pendent of Length and Strength of Needle, 91 Tangent, Sensibility of, In- versely Proportional to Dia- meter of Coil, 98 Tangent, Sensibility of, Method of Increasing, 91, 98 Tangent, Sensibility Propor- tional to Number of Con- volutions of Wire, 98 Tangent, Sensibility of, Re- strictions in Increasing, 98 Tangent, Sensibility of, Varies with Strength of Controlling Field, 102 Galvanometers and Ammeters, How Straight Line Law Obtain- able in, 125, 132, 137, 147 Joint Relative Calibration of, 238 of Invariable Sensibility, 127 Proportional, 124 and Voltameters, Relative Ad- vantages of, 42 Galvanosccpe, Definition of, Note, 43 — — Deflection of, Not Proportional to Current Strength, 22 Description of, 10 and Resistances, Comparing E.M.Fs. of Cells with, 502-510 Gas, Current of, Measuring Distri- bution of Pressure in , 1 58 - — Pressure Compared with Elec- tric Potential, 201, 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 Dry Cell, 458 Gauss's Absolute Unit of Force, 571 Generator of Current. 