None
The following experiments have been devised to make the student {Hmctically acquainted with the effect of shunting a galvanometer, and the manner in which the effect of a given shunt depends on the resLstance in the other parts of the drcuitb The resistance of the galvanometer circuit unshunted is about 200 ohm& ExPEBiMENTS. — (1.) Using one cell of the battery, and with no resistance in the main circuit excepting that of galvanometer, battery, and connecting wires, send a current through the unshunted galvanometer and note the deflection d produced. (2.) Place various resistances from the highest avail- able down to 0 in the shunt circuit, and note all the corresponding deflections. (3.) Tabulate your results in some convenient form. IK8TBUOTION8 FOB BZPniMBNTB. 479 (4.) Plot a curve having for abscisssB the resistances in the shunt circuit, and for ordinates the corresponding currents passing through the galvanometer. (5.) tfoin up two cells of the battery, and introduce such a resistance into the main circuit as will give the same deflection d as was obtained in (1) when the galva- nometer .was unsliunted. (6.) Repeat (2), (3), (4), drawing the curve oh the same e^eet of paper. (7.) Repeat (5) and (6), using four and six cells re- sjiectively. DEDUCTION& — Write out a clear account of the in- ferences which yon can draw from these experiments. Also determine al^braioally the general eqaation to, and oharac* tflr of, tiie eniree obtained in theee experimenti, and show how the results obtained experimentally oonld be dednced from thie equation. Prove that the cunree have a common asymptote, and find the limits between whioh the other asymptotes lie. 480 PRAOnOAL ELSCraiCITT. CITY AND GUILDS OF LONDON INSTITUTR OBMTBAL INSTITUTION. PHYSICAL DEPARTMENT. Vo CALIBRATE an AMMETER by the CALORIMETRIC METHOD. PRBUMINABT. — ^The ctdoiiineter provided consists of a thin copper vesael supported within an air space, and screened from external radiation bj a large water jacket A coil of German silver wire is inserted in the calori- meter, and sarrounds the bulb of a delicate thermometer. This Uiermometer serves to show the rise of temperature of the water and calorimeter caused by passing a current through the wire. Another thermometer indicates the temperature of the large water jacket in which it is im- mex«ed. EzpKRiMENTS. — (I.) Carefully dry and weigh the small copper calorimeter, the approximate we^;fat of which is 24*8 gramme& (2.) Partly fill tlie calorimeter with distilled water by means of the pipette provided, and determine the weight of the water added. (3.) Replace the calorimeter within the water jacket and connect the wires to the ends of the ooiL Adjust the pointer of the ammeter to zero (if necessary) by turn- ing the small milled head at the top. (4.) Complete the circuit, and adjust the carbon re- sistance till a suitable deflection is obtained on the am- meter, say 0*8, which must be maintained constant. Keep the water well agitated by means of the stirrer, and take '* time readings " (about every half-minute) of the temperatures of the inner and outer vessels, until the inner thermometer has risen several degreea Break the circuit. nraTRUCTIORB FOR BZPIBIMBNT3. 481 (5A Tabulate your results in a convenient form. (6.) Plot a curve having timea for abscissfle and tem- peratures of the calorimeter for ordinates. (7.) Repeat (4), (5), (6), using successively currents which produce deflections of about 1*1, 1*4^ 1*7, and 2*0 on the ammeter. (8.) When all the heating observations have been taken, break the circuity and allow the calorimeter to cool to nearly its initial temperature, and take time readings of its temperature, keeping the water well stirred all the while. (9.) Plot a ** cooling owrv9^ from the observations obtained in (8). (10.) Correct the heating curves obtained in (6) and (7) by the cooling curve (9), and determine the corrected rise of temperature in a given time (say five minutes). (11.) Calculate Uie strength of current passing in each of the above experiments from the formula 'V 0-24 X r<' n where A stands for the current in amperes, „ r „ „ resistance of the coil in ohms, which is 1-0306 at 15°-6 C. W ,, „ weight of the water in grammes, to „ „ water^uivalent of the calori- meter, thermometer, kc., which equals 2*778 grammes, „ T „ „ corrected rise of temperature in t seconds, „ t „ „ time in seconds, and compare the values so obtained with the graduations of the ammeter. Deduotions. — State clearly how the heating curves are corrected from the cooling curve so as to show what would have been the true rise of temperature if no oooling had taken place during the experiment. 482 PRACTICAL ELEITTRICITT. CITY AND GUILDS OF LONDON INSTITUTE CENTRAL INSTITUTION. PHYSICAL DEPARTMENT. To CALIBRATE an AMMETER by means of a SILVER VOLTAMETER. Preliminaet. — ^The voltameter consists of a platinuin dish containing a 25 per cent, solution of silver nitrate, and in which a silver plate is immersed. An adjustable carbon resistance is provided, by means of which the cur- rent passing through the voltameter can be maintained constant during each experiment, and can be varied in the different experiments. Experiments. — (L) Carefully clean, dry, and weigh the platinum dish, the approximate weight of which is 78 grammes. (2.) Pour the solution of silver nitrate into the dish and place it on the three brass pins provided for its re- ception, and which are electrically connected with the left-hand binding screw on the board. Immerse the silver plate in the solution, and clamp it in such a posi- tion that its edges are equally distant from the sides and bottom of the dish. (3.) Turn the small milled head at the top of the ammeter so that the pointer of the ammeter comes oppo- site the zero on the scale, if not there already. Place the copper connecting wire in the mercury cups marked A and 0 (which cuts out the voltameter), and adjust the carbon resistance until a convenient current flows round the ammeter. Kemove the connecting wire. (4.) Quickly insert the connecting wire in the mer- cury cups marked A and B, carefully noting the instant at which the circuit was completed Allow the current IKSTBUCTIONS FOB EXPERIMEKTa. 483 to pass for a oonvenient time (10 to 30 minutes, accord- ing to the strength of current used), and keep the current constant by the adjustable i*esistance. Note the tem- perature of the room during the experiment, and, at the end of the interval decided on, quickly break the circuit. (5.) Empty the solution from the dish into its bottle and carefully wash the deposited silver with distilled water. Then fill the dish with distilled water and allow it to stand 10 to 15 minutes. Again wash with water^ alcohol, and ether, dry over the spirit-lamp, and cool in the desiccator. (6.) Carefully determine the increase of weight due to the silver deposited on the dish. (7.) Calculate the strength of current used in the experiment, assuming that one ampere deposits 1*11815 milligi-ammes of dilver per second. (8.) Hepeat the experiment with several different strengths of current. (9.) Tabulate your results in some convenient form and write them with your name on the card, on which you will find recorded the results of previous experiments. INDEX. A BSOLUTE Calibration, QalTa- nometera wxth Invariable, 57 — - Oolibration of Qalvanometers, SO. 38&-400 Calibration of a QalYanometv*, Meaning of, 22 — Calibration of Potential Differ- ence QalTaAometers, 127, 408-415 Calibration, PortaUe Oalvaiio- meter with Approximate, flB— 71 Electrometer, 93 Measurement of Oapadty, 327 Unite. 141 Accomalating Influence Machineas 361 ; Uoltz's, 387 ; Nichol- son's, 366 : Thomson's, 364 ; Tarl^'8, 367; Yoas, 367; Wimsburst. 367. {See also Influence Machines.) Accamnlator, Measoring Beeistanoe of, 206 Accumulators, Small Internal Re- sistance of, 206, 261 Accuracy of Grodoation, Testing Ammeters for, 305 of Graduation, Testing Volt- meters for, 406 of Beadings with Tangent and Degree Elcales Coinpared.40 Acid, Dilate Sulphuric, £ffect of Electrolysis of, 15 Sulphuric, voltameter. (Set Sulphurio Acid Volta- meter.) Action, Inductive, 87 of the Electrophorus, 356—361 Adjustment for Sensibility in Mag- nifving Spring Ammeters and Voltmeters, 389 — of Coil of Tangent Galvano- meter, 46 Advantage of FoggendorfTs Method of Comparing Electro* motive Forces, 236 Advantages of Cardew's Voltmeter, 426 of Cunynghame's Ammeter and Voltmeter, 385 — — of Electro-Magnetic Control Meters, 894 Advantages of Gravity Control Meters, 391 of Magnifying Sprhu Ammeter and Voltmeter, 390 '>fPennauentMagn0tMeter8,78 oj Shielded, Dead -Beat, Di- rect- Beading Galvanome- ters, 78 of Siemens' Eleetro-Dynamo- meter, 380 — — of Thomson's Large Current Galranometer, 53 — ^ Belative, of Voltametsra and Gkdvanometers, 2i) Air Condenser, Standard^ 334 Specific Inductive Cfapacity of. at Different Pressures. 310 Alternating Currents, Definitiou, and Measurement of, IdB, 381 Potential Difference Increases Practical Besistanoe of Voltmeter, 427 — - Potential Difference, Measur- ing, 426 Aluminium, Besistance of, for Given Length and Diameter, or for Given Length and Weight, 157 Besistance of, per Cubic Centi- metre, and per Cubic Inch, 154 Amalgam, Definition of, 218 Amalgamate, How to, 218 Ammeter, Advantages and Disad- vantages of Cunynghame's, 38o Advantages and Disadvantage of Permanent Matjnet, 78, S76 Advantages and Disadvantage of Magnifying Spring, 3'JO Adjustment for Sensibility m Magnifying Spring, 389 -— Calibrating Commutator. 432 Commutator ,De8cription of ,427 Commutator, Safety Arrange- ment with, 432 Cunynghame's Description of, 382 Graduation of Cunynghame's, 385 — for Large CurrentH, Use of Commutator in Calibrating. 488-481 186 FBACTIGAL BLBCTRICITT. Ammeter, Indication of Direction of Carrent in Magnifyinff Sprinir. 389 ^— Macnuf^^ Spring, Description -—Permanent Magnet, Deaorip- tion of, 76 — — Permanent Magnet, Propor- tional, 71 Ratio of Sensibilities of Gom- mntator in Parallel, sxid in Series, 431 AmmeterB,76-79, 382, 886l (SMalw> Meters.) Calibratinflr, bj the Silver De- posit Method, 985-400 — Testing, 8M Testing, for Accaza<7 of Gra- duation, Sd5-400 •— — Testing, for £rror on BeTersing Current, 402 —-Testing, for Error Prodnoed by External Ma^oietic Dis- turbance, 408—407 — — Testinir,for Permanent Altera- tion o! Sensibility. 407 — — Teetinfr, for Besidnal Mag- netism, 400 — with Maguifymv Gearing, 886. (Sm also Dynamometer, Galyanomet«-r.) Amount of a Body's Electrification, 109 —— of Electricity, Dependence of Potential of Conductor Partly on, 119 ^— of Heat produced per Minute by Given Curreut FJowing through Given Besistance, 1&9 — ^ of Heat produced jier Minute, Measurement of Currents bv, 197 Ampere, Definition of the, 11 Amperes, Yalnes in, of Deflections of Tangent Galvanometer, Controlled only by Earth's Magnetism, 55 Angles, Finding, from their Tan- gents by means of Squared Paper,56 ——-Finding Tangents from, by means of Squared Paper, 67 Angular Deflection of a Mirror. Counection between, ana Motion of Image on Plane Scale, 107 ^^ Deflection Proportional to Cur- rent, Construction of Gal- vanometers with, 71—73 «-. Motion of Befleoted Bay is Twice Angular Motion of Mirror, 106 Antimony, Change of Besistance of, with Temperature, 160 — Beeistanoe of, for Given Length and Diameter, and for given Length and Weight, 157 Besistanoe of, per Cubic Centi- metre, and per Cnbio Inch, ide Apparatus for Measoring Yariatiaai of Current and Potential DilTerenoe at Battery Ter- minals with Variation of External Besistanoe, 205 •^— Static EleotriCj Kecessaiy En- dosare of, in Metallic Case* 108 Apparent Increase of Besistanoe in a Galvanometer Due to Damping, 340 Approximate Absolute Calibration, Portable Galvanometer with, 60— 71 Are, Electric, Description of, 188, 454 Electric. Measuring Dluminat- ing Power of, in Any Plane, 457 — — Light, How to Overcome Differ- ence in Colour between it and Candle when Measur- ing. 457 — Light, Measuring the Efilciem^ of. 455 -^-Potential Differenoe Bequired to Maintain an Electric, between Two Carbons, 871 Area, Sectional, Yariation of Be> f>i9tanoe with, 146 Arms of Wheatstone's Bridge, Defi- nition of, 172 Anangenient for Shunting Battery while Charging Condenser <miy,843 cA Cells, giving Maximum Use- ful Power to Conductor of Fixed Besistanoe, 450 of Given Numbtv of Cells to produce Maximum Current through Given External Besistonce, 243 Arrangements of Cells, 230—253 Astatic Combination of Magnets^ 283 *— Galvanometer, Advantage of Putting Mizror Outside Coilsi^ —— Galvanometer, Simple Method of Damping, 284, 300 — — Galvanometer, Mather's, 2B0 IHDBZ. 487 Aatatie GalTaaometer, Mndford*!, 105 —— GttlvanoiiMter, Thomson's, 288 QaWanometcr, Thomson's Mftiified,SB4 Attaching Lmden Jars to Colleot- vag Combs of Electrical Ibehioes, 370 A.ttraot<nff Force, Potential Difl^- enoe and Distance between Two Parallel Plane Con- dnotors, 87 Axis, Haflrnetic. of a Needle, Defloi- non of, 87 B I3ALANCE, Wheatstone's, ld»- -" 177. (Sm also Wheatstone's Bridge.) Ballistic QalTanometer, 292 Batteries, 200 ; Bnnsen's, 219; Cal- laud, 213; Dauiell's, 211; Oravitj. 212: Orove's, 218 ; L(>c]anch^, 220; Lockwood, 218; Meidinffer. 212: Hin. otto's, 211 : Potash Bichro- aiate, 222; Hecondary, 206, 261. (Se« also Cells.) *»-Compaiiaon of Electromotire Forces of, by Ob^errins tbeir Joint and Opposea Currents, 232 — Comparison of Eleotromotiye Faroes of, by Obsenriog Beslstance through which they send Equal Currents, 231 V— Comparison of EleotromotiTe Forces of, Condenser Me- thod of, 3*1 •— Comparison of Electromotire Forces of, Poggendorffs - Method of, 24i — ^ Local Action iu, 217 — » Measuring Besistanoes of, 205, 225.342 — ^ Polarisation in, 216 Figures of. 2%) — ^SymboUcal Bepresentation of, 173,240 Battery and GalTanometerinWhoat- btoue's Bridge, Best Ar- rangement of, 172, 467 ^— ArrangemeDt for Shunting while Charging Condenser only, 343 — ' of Leyden Jars, 817 ^— of Simple Voltaic Elements for Chsjxing Electrometer Needle, 373 B. A. Unit of Besistsnce, Ul B. A. Unifa and Legal OhmsL Equa- tion Connecting, 142 Bell Telephone, Description of, 836 Bertsoh*0 Botatory Eleetrophorus, 861 Best Axxanffement of Battenr and GolTunometer in wheat- stone's Bridge, 172, 467 — Deflection to use with Tangeni Galvanometer. 41 Besistanoe for Coils of Wheat stone's Bridge, 170 Beaistunce for DiffereBtial Gal- Tanometer, 486 —^ Beslstance for Gklnuiometer in Simple Circuit, 435 —^ Bedstance for Galvanometer iu Wheatstone's Bridge, 171, 466 Besistanoe to GiTe toa GalTano- meter^485 Bichromate of rotash Cell, Descrip- tion of, 222 of Potash Cell. Chemical Action in, 223 of Potash Cell, Composition of Liquid for. 22i of Potash Cell, klectromotive Force of, 228 Bismuth, Change of Besistanoe of, with Temperature, 160 Electric and Heat Conduotiyi- ties of. Compared, 159 — ^ Besistsnoe of, for Given Length and Diameter, and for Oiven Leugth and Weight, 157 — Besistanoe of, per Cubic Centi- metre, and per Cubic Inch, 154 Bobbin of Tangent Galvanometer, Proportions of Channel in, when Tangent Law is most Accurately Fulfilled, 51 Vsriation of Msgnetio Effect of, with Currunt sad BecLit- auce, 418 Variation of the Sensibility of a Tangent Galvanometer, with Diameter of, 48-^51 Bridge, Wheatstone's, 16d— 177 Wheatstone's, Best Arrange- ment of Battery and Gal- vanometer with, 172, 467 Wheatstone's, Best Besistanoe of Galvanometer for, 171, 466 Wheatstone's, Best Besistanoe of UoUs for, 171 -~~ Wheatstone's, British A<nooia- tion Form of, 168 488 PRACTICAL ELSCTRICITT. Bridge, Whefttstone*!, Oommanaal Form of, ITS — WhcAtatone't, Conditions Af- tectiag SensibiUtj of. 171 — ^ Wbeatstone't, Key for, 174 — WlieatBtone's, M««ning of !>«• Hectiou of QftlTMiometer of. 176 — WtaflatsUma's, Metre Form of, 188 — Wheatstone's, Saperioritr of, over Differential Oelveno- meter, 171 Wheatstone's, Uae of Skimt with, 176 firitiah AModation Abaolute Units, 141 Association Bridge. 168 Assoeiatioii Unit of Eesistanoe, 141 Brush Discbarge, 369 Bunsen's CelL DescriptioB of, 219 Cell, Carbon for, 8M Cell, Chemical Action in, 219 -^— Cell, ElectromctiTe Force of, 220 Butt Joint, 79 0 rjABLE, Capacity of a Sabmsrine, —— BealiBfr ap One End of, when Testing, 268 Calibrating Ammeters b; the Silver Deposit Method, S9&— 400 Ammeters for Large Currents, Use of Commutator for, 428 — — Commutator Ammeter. 482 — — Commutator Voltmeter, 433 •^— Gulvanometer by Direct Com- parison with Tangent Oal- Tanometer, 58 — " Galvanometer b^r Employing Known Besistanoes and Cell of Constant E.M. F., 2:t8 —— Oolvauometer by Employiniar Kuo«^n Resistances aud Fixed Puteutial Differ- enoe, 164 — — Galvanometer by Sine Method, 64 •»— Golvnuometer, by Sine Method, Higlier Kartsof Scale of, 65 — — Gnlvauometer by Sine Method with Constust Current, 67 —— Galvanometer, Relatively or Abe<-lurely, Meaning of, 22 — Galvanometer, Relatively t-r Alisolutely, Modoof, 27—30 »— G old-Leaf Electroscope, S54 CalibEKfciBg Voltmeter by Compaii- son with Standard Cell, 4ia->415 -— • Voltmeter by Poggendoiff s Method, 413 — Voltmeter with a Known Cur- rent and Reaietanoe, 406 CalibratiozL, Absolute, of Potential Difference Galvanometer, 127,408-^415 — — of Galvanometer UnaflTeeted by Changs in Streogth,of Poles of Iffeedle, 23 Galvanometers with Invariable Absolute. 57 Portable Galvanometer with Approximate Absolute, 6B Calktud Cell, DssoriptioD of, 213 Candle, Description of Standard, 458 Candles instead of Standard Can- dies for Rough Experi- ments, 46fi Capacities, Comparison of, 319 Statical Method of Comparing, 830 Oapaei^, Abaolute Measurement of, 327 Charge iu Terms of, 303 Construction of Condensers of Very Lsrge, 317 Definition of. 90O Measuring Speoiflo Inductive, 382 -^— of Condenser is Constant, 302 — — of Condttuer, Variation of, with Area of its Coatings, 303 — of Condenser, Variation of, with Distance between its Coatings, 308 <rf Condenser, with Fbne Parallel Plates, varies in- versdj as Distance be- tween its Coatings, 307 — - of Cylindrical Condenser, 303 of Sphere in Space, 830 ——of Spherical Condenser, 338 — r- of Submarine Cable, 303 of Collectors of Influenoe Ma- chines, Increasing the, 370 -^— of Two Bodies Constant while their Relative Positions are Constant, 838 Unit of, 307 Specific Inductive, 309 Carltonic Dioxide, Speciflc Induc- tive Capacity of, 310 Carbonised Cloth. Preparation of, for Varley's Resistances, 3^ Carbons for Bunsen's Cells, Mode of MaJdug, 220 Curdew's Voltmeter, Description of the Latest Form of, 4^ .m-hA IKDBX 489 Oaidew'BToltmetar, Adnrntages of, 420 •— ^Yoltmeter Amiumd for MeasoxiniT iMCKe Potential DiffereBcea, 425 — — Yoltmettf, Coniitmotioii of Sods in, to FzeTent Change of Length with Tempers- tore, 426 —— Voltmeter, Diameter of Wire used in, 423 Voltmeter, Disadrantagefl of 427 —— Voltmeter. Length of Wire used in tne Latest Form of, 423 '—— Voltmeter, No Heating Error in, 428 -^Voltmeter, Small Self-Indac- tion in, 427 Cell, Baiisen's, 219 Calland, 213 IXaniell's, 210 Fleming's Standard Darnell's, 412 QraTit J DanieU's, 212 Orove's, 218 Ijedanch^. 220 Latimer Clark's, 410 Lockwood's, 21ii Meidinger'fi, 212 Minotto'6; 211 Potash Bichromate, 222 Standard Daniell's, 411 Chemical Action in a Bonaen's, 220 Chemical Action in a Daniell's, 214 —— Chemieal Action in a Grote's, 219 Chemical Action in a LecJanoh^, 221 — — - Chemicsl Action in a Potash Bioliromate, SffiS ^^ Carbon for Bnnsen's, 220 —— Composition of Liqnid for Pot- ash Bichromate, 222 Constancy of E. M. F. of a DanieU's. 216 — Constancy of E.M.F. of a Latimer Clark's, 411 E. H. F. of a Bansen's, 220 £. M. F. of a Daniell's. 211 E. M. F. of aStandard DanieU's, 412 -— E. M. F. of a Grove's, 218 E. M. F. of a Latimer Clark's, 411 —^ E. H. F. of a Leclanch^, 222 E. M. F. of, Independent of Size an.l Shape, 211, 236 •^E.M.F., Temperatore Varia- tion of, in Latimer Clark's^ 411 Cell, E. H. Fs. Charge, Measuring Beaistaiioe by Bate of Lom of, 843 — Bemaining on Two Bodies after Ck>ntact, 115, 851 Charged Body cannot Exist Alone, 339 Charge! induced in Hollow Con- ductor hy phioing a Charged Body inside it, 113 *— on Two Conductors Enclosed hy a Third. 110 -—on Two Bodies not Measured hy the Potential jyiSar- ence, 85 Chemical Action in the Bunsen's Cell, 220 Action in the DanleU's Cell, 214 Action in the OzoTe's Cell, 219 •^—Action in the Leolanch^ Cell* 221 — — AotJon in the Potash Bichro- mate Cell, 223 •~— Property of a Current, Uses of, 4 — Property of a Currant, Whr Used to Measure Strength of Current, 9 Cironit, Law Couneotiug Currents in a Closed, 404 Wires Joined in Parallel, 136 Circuits in Parallel, Independence of Currents in, 260 Clark's, Latimer, Ditferentisl Oal- ranometer, 150 Latimer, CelL 410 —~ Latimer, Cell, Constancy of K.M.F. of,4Il — — Latimer. Cell, £. M. F. of, 411 -^— Latimer, Cell, Polarisation of, 411 — — Latimer. Cell, Temperature Variation of E. M.F. of, 411 Closed Circuit, Law Connecting Currents in, 461 — - Conductor, Density Nought on Inner SurfHce of, 118 — — Conductor, Distrihution of Density in. Altered hy In- sertionof Metal Rod, 119 ••— Conductor, Potential Inside, 96 Cloth, Preparation of Carhonised, for Yarley's Besistances, 397 Coating Insulating Stems with ParaflSn Wax or Shell-lac Varnish, 267 ^— of a Condenser, Every Charged Body forms One, 393 Costings of a Condenser, Definition 0^802 Coll of Tangent GalTsnometer, Ad- justment of, 46 Coils, Besistanoe, Constmcttom and Use of, 28, 145 Besistanoe, Conatmeyoa of Standard, 162 — >— Besistanoe, Materials Used in Winding, 159 Resistance, &erm«n Silver, 160 Resistance, Iron, 162 Redstaiioe. 491 Comptmg EleotromotiTe ForeM of Batteries bj Obeerrinff the Beeietanoee thronjrh wnicli th^ send Equal Ciirrents, 231 ^— ElectiomotiTe Forces. Condcn- ser Method of, 841 — — Electromotire Forces, Poggen* dorffs Method of. 234 Qaantities of Eleutricity, Fun- damental Statical Method of. Ill Qaantities of Electricitj, Oal- Tauometrio Method of, 299 Besistanoes, Equality of Cur- rent Method of, 136 Besistanoes, Potential Differ- ence Method of. 140 Besistanceff, Simple Substitii- tion Method of, 138 Besistanoee, Use of Differen- tial GhilTanometer for, 148 —— Besistances, Use of Wheat- stone's Bridge for, 97 Comparison of Difference of Poten- tial with DifFerenoe of Level in Liquids, 86 -^— of Difference of Potential with Difference of Pressure in Oases, 86 •^^of Electric and Heat Conduc- tivities, 158 of Measurement of Poteittial with Measurement of Tem- perature, 85 — — of Beststanoe per Cubic Centime- tre, and per Cubic Inch, 348 of Static ana Current Methods of Measuring Potential Dif- ferences, 125 of Use of Liquid and Wire Be* sistances, 194 Component, Horizontal, of the Earth's Magnetic Force, Definition of, note^ 55 ComxKwition of Liquid for Potash Bichromate Cell, 222 Componnd Interest Law of Electxo- phoric Action, 366 Interest Law of Slectrophoiic Action, when firstiUsed, 366 ——Interest Law of Influence Ma- chines, 364 Oondeufier, Arrangement for Shunt- ing Battery only while Charging, 348 Capacity of, 302 Capacity of Cylindrical. 308 Capacity of Spherical, S38 Coatings of, 302 Constancy of Capacity of, 808 — Definition of, 801 Condenrer, Bresy Charged Body forms On«> Coatingof oJSSa — Method of C' mpuring E.M.F8., 341 Method of Measuring Besist- ance of a Current Genera- tor, 842 — - Standard Air, 884 -^— Variation of Capacity of, with Area of Coatings, 803 — — Variation of Capacity of, with Distance between Coat- ings, 303 with Plane Parallel Plates, Ca^ pacity of. Varies Inverselr as Distance between Coat- ings, 907 Condensers for Large Potential Dif- ferences, Construction of, 313 for use with Frictlonal and In- Quence Machines, 313 not Stores of Electricity, 822 —^ of Very Large Capacity, Con- struction of. 817 Stores of Electric Energy, 822 Condensing Electroscope, 352 Conditions affecting Sensibility of Wheatstone's Bridge, 171 General, for Sine Law to be True. Coadaetor, CooJoftLElMtrJo T)eiiflitT GreRt at Pointed End o^ 118 A—- Dependenoe of Potential of, on Amount of Electrieitj on it, 119 -'— Dependenoe of Potential of, on Position. 119 ^— Dependenoe < f Potential of, on Shape, 119 ^->- Electno, Heat evolved in, S, 199 Electricity at Beat resides only on Surface of, 119 -— of Fixed' Beaistitnce, Anange> moat of Cells Kivinf? Maii- muxn Usefnl Power to, 450 Potential inside a Closed, 98 — — Potential of, compared with Pressure of Gas, 121 Uniform Potential on a, 86 Ways in which Potential of, canbeYariad, 121 Conductors, 9 •— Charges on Two, Enclosed by a Third, 110 •— — of Diffidnent Potential, Induc- tive Action lifetween, 87 Conical Conductor, Electric Denaitr Great at Pointed End of, 118 Connection between Angular Motion of Beflected'Kay and of Mirror, lOd ——between Motion of Image on a Plane Scale and Anirul.>r Deflection of Mirror, 107 — — between Poles of Magnet and Direction of Current cir- culating round Magnet, 17 Constancy of Capacity of Condenser, 30*^ •~— of Capacity of Two Bodies while tiieir Belative PositionB •rooiain Constant, 338 of E.M.F. of DanieU'a CeU. 216 of E. M. F. of Latimer Clark's Cell, 411 *— of Bate of Production of Heat bi a Wire by Constant Cur- rent, 197 Constant Current, Calibration by Sine Method with, 67 of a Galvanometer, 278 — — Total, Current Sbuuta, 257 Constructing Voltameters, Objec- tions to usual Mode of, 17 Contact Potentiid Difference, 351 Controlling Field, Galvanometer having Uniform, in which Deflection Varies as Cur- rent, 72 OontroUing Foroacansed hf Powck fill Pennanent Magnet Galvanometers havinip, 73 Convection of Heat, nMe, 196 Cooling Correction of Observed Bis. of Temperatuvs Cnrre^ 19^ Copper, Chaiwe of Besistonoe of, with Temperataz«, 160 — Electrio and Heat CondnctiTl- ties of. Compared, 159 — — Besistanoe of, for Grven Length and Diameter, end fc Gi^en Length nd Weigtac, 157 '— Besiatanoe of, per Cahic Ceati- metre, and per Cnbic Inch, 154 Voltameter, Doscrii^tion of, 6, 11 Voltameter, Direction at Cur- rent in, 15 -^— Voltameter, Precantkma in Usii^, ntft«, II "— Voltameter, Weight of Copper dt'poeited on Plate of, per second, by one Ampere, 11 Corea, Soft Iron, used in Ghalvano- mettra, 73 OoiTTeeting Results of ExptnimeiitB by Drawing Curves, 34 Correction, Cooling, of Observed Biae of Temperatura Curve, 196 Correction for Damping. 296 Corrugating Sides of Ebonite Pil- lars, 272 Coulomb, DefinitioB of the, 289 Couple. Defluition of. fuU, 2SS Defluition of Moment of n, «cf«. 283 Crompton and Kapp's Electro-Mag- netio Control Meters, 898 and Kapp's Electro-Magnetio Control Meters, Advant- ages and Disadvantages oL 384 Cunynghame's Ammeter and Vol^ meter, 8^2 — -Aminet^ and Voltmete^ Ad;* vantages and Disadvan^ ages of, 385 •— Ammeter and Voltmeterp Graduation of. 385 Current, Alternating, Definition of, 198 Alternating, Measurement oL 198,381 Amount of Heat Generated by Electric, 192 —— Amount of Heat produced per Minute by given, in given Besistanoe, 199 Amingement <^ given Numbei IKDEX. 493 «f Cells to'produoa Mui- mnm, thiongh given Ex- ternal Beeistenoe, 248 Cozrent and Besistanee, Yaziatdon of Kagnetio Effect of Bobbin ^^th,418 ^-» and Static MetJioda of Measu- ring Potential Differencee Compaxed, 125 Calibration by Sine Method with Constant, 67 — ConuneoKsial InstramentB for Meaeoiing, 79, 376 —— Connection betweea Dizeotion of, and Poles ol Magnet piodnoe^, 17 — — Constancy of Bate of Prodno- tion of Heat in a giren Coa by Constant^ 107 Definition of Direotion of, 14 ^— DeTeloping Masimun Usefal Power in Oenentor with Fixed E.M.F. and Besist- anee,4i8 -^- l>irBction of, in Add, Copper, and 2Uno Voltameters, 15 — — Dxreddon of, ronnd Msgnet^ and Poles ptodaced, 17 -—Electric, Compared fdtii Cva- rent of Water Jt,80 Electric, Heat is Evolved by, 8 •^— Electric, Liqcdd is Decompcwed by. 8 Electric, Magnet is Deflected by, 8 <— ^ Electric, Propertiee of, 8 Electric, What is Meant by, 2 Electric, When said to Flow in a Condootor, 8 Flowing in Flat CoiL Direction of Magnetic Force pro< diicedby,48 Cenerator, definition of EflU ciencyof,461 — Generator, Measurement of E. M. F. of, 224, 231, 23i, 841 — Qeoerator, Work done by a, 202 Generators, 2Qa (Sm also Cell and Batteries.) ^— Increase of TotaL hy Shnntiiig, 188 ^»- Indication of Direction of, in Magnifying Spring Amme- ter and Voltmeter, 88B — » Measoring Alternating, 196 — - Measuring, by Bate of Produc- tion of Heat, 197 *-" Measuring Strength of, 4^ 8 —^Measuring with Siemens' Dy- namometer, 879 Measaring Besistance during of Strong, 187 Current of Water fa. Pipe Compared with Electric Current, 80 Properties of, 8 Proportional to Tangent ol Angle in Tangent GalTa- nometers, 43 Batio of, to Potential Differ- ence Constant for GKven Conductor, 190 — Besistanoe Coils Heated Vj Strong, 192 — BeversiDg, without Altering iti Value, 47 Strength, Why Measured Fan- damentally by Chemical Property, 10 Testing Ammeters for Emnr on Berersing the, 402 — that Develops Maximnm Use- ful Power, 448 through the Galvanometer of Wheatstcne's Bridge, 435 Unit of, U Variation of, with Variation of Potential Difference at Battery Terminals, 204 -^ Variation of, produced m Total, by Shouting Part of Cir^ cuit,258 What is Meant Vy, 8 Currents in Closed Circuit, LawCon- neoting, 464 in Network 462 in Various Circuits in Parallel, Condition of Independence of. I) "nAMPIKa. 291 '^ — — Apparent Xnereaae in Be* ri«t>noe of a Qalvanometer due to, 819 '— Correotion for, 296 Definition of, 284 Daniell's Cell, Deaoription of, 210 Cell, Chemical Action in, 214 Cell, Constancy of E. M. F. in, 216 CeU, £. H. F. of. 211 CeU, E. M. F. of Stanaazd, 411 CeU, OraTlty, 212 CeU, Fleming's Standard, 412 CeU, How to PreTent Local Action in, 217 CeU, Polairiaation in, 216 — Cell, Beaiataaee of, 211 CeU. Standard, 411 Dead-Beat, Shielded, Direot-Bead- ing Galvanometers, Ad- Tantagea of, 78 Decromant, Determination of Log- arithmic, when Damping is Very SUght, 297 ^~ Logarithmic, 296 Definition of Alternating Corroni, 198 — — of the Ampere, 11 — — of Brush Discharge, 869 of Capacity, 800 <— of Capacity of Condenser, 802 of Condenser. 801 of Condnctivity, 155 — of Contact Potential DifKarenoe, 351 of the Conlomht 289 of Conple, 283 of DifFerenoe of Potentials, 80 ^~ of Damping, 281 of Dielectric, 311 — of Direction of Current, 14 — — of Efficiency of Corrent Qene- rator, 451 — of Efficiency of Electric Light, 4SS of Elastic Cnrre, M — of Electric Density, 117 — — of Electromotire roroe, 202 of the Farad, 307 -~— of Ghdvanometer, iu>U, 21 of Galvanosoope, ^mAs^ 21 of Glow Discharge, note, 869 of Hermetically Sealing, noU, 20 — — of Horixontal Component of Earth's Magnetic Force, nAf«, 55 -^— of Hypotenuse, tiots, 38 ^— of Inductive Action, 87 — — of the Jonle, 461 Definition of Lines of Force, 4S —-^ of Logarithmic Decrement, 896 of M^netic Axis of a Needle, 37 '—' of Magnetic Saturation. 388 — of Moment of Couple. i>o(f, 28S •— of Moment of Inertia, 78 of North-eeeking End of Mag- net, 16 of the Ohm, 140 of Parallflx, aotf , 88 of Periodic Time of Txhration, 291 ■ — of Plane of Magnetic Meridian, note, 45 — of Potent-'al Diiferenoe, 80 of Power, 441 of Quantity of Electricity. 109 of Besidual Magnetism, 385 of Betardation, 331 of the Saturation of Liquid, 411 of Short-Cirottited, 217 of Sine, tiota, 38 of Solenoid, nnts, 887 — — of Si>ecifio Indactive Capacity, 309 — of Striking Distance, nvk*^ 371 of Snper-ntoration, not*, 411 — of Tanxent. note, 37 of tbe Yolt, Legal, 141 of the Volt, Prortsional, 89 of Uniform Magnetic Field, 88 of Water Equivalent, 1S6 of the Watt. 495 ■llv BHeotrio, Definition of, 117 Electrxc, Onat at Pointed End of a Conical Gondactor, 118 Electric, Greater near Edges of Flat Sheet of Metal, 118 '—— Electric, Meaeuring, by means of Proof Plane, 117 Electxio, Nonght on Inner Sur- fnoe of CloBed Conductor, 118 — — Electr c. Potential, and Qnan- tity. Examples showing Diilerence between, 121 Dependence of Kate of Loss of Charge on Dielectric Only, S46 Depres, £. M. F. nsed by, in Trans- mittiDg Power Thirty- seren Miles, 4&2 Detector, 58 Determination of Logarithmic De- crement when Damping is ▼ei7 Slight, 297 Diameter of Bobbin, Variation of Sensibility of Galvanome- ter with, 48 Dielectric, Definition of, 311 Only, Dependence of Bate of Loss of Charge on, S47 Difference between Saturation and SuperHsattiration, noUf ill «— in Colour between Candle and Arc Light, How to Over- come, in Measoring Arc Light, 457 -^— of Potentisd, Adjusting Balls of Electrical Machine to produce Given Maximum, 372 — of Potential, Alternating, In* creases Practice Kesist- ance of Voltmeters, 427 — ^of Potential, Alternating, Mea- suring, 426 — • of Potential at Battery Termi- nals, Variution of, with Chaiage of Current, 204 •'—of Potential between Two Conductors not Meosaring Difference in their Electric Charges, 85 *— — of Potential between Two PlflAe ConductorSyFormula connecting, with Distance and Attraction between them, 87 — -xif Potential between Two Points in a Uniform Wire Conveying Current Pro- portional to Distance be- tween them, 83 — o( Potential Charges on Two Conductors Tary as, while their Relative Positions re- main Constant, 110 Difference of Potential Compared with Differoace of Level in Liquids, 86 Potential Compared with Difference of Pressure in Gases, 86 Potential Compared with Difference of Pressure of Water Flowing in a Pipe, 81 Potential, Contact, 351 Potential, Definition of, 80 Potential Galvanometer Ab- solutely Calibrated, 127, 406,415 Potential Galvanometer, Long Fine Wire Used in, 127 Potential GMvanometer, When itmiqr be Employed, 127 Potential, Increasing a, in Known Batio, 354 Potential, Large, 351 Potential, Measuring, by Weighing, 88 Potential Method of Com- paring Resistances, 140 Potential, Ratio of, to Cuz^ rent. Constant for Given Conductor, 130 Potential, Ratio of, to Car. rent is Resistance, 130 Potential Required to Main- tain Electric Ato between Two Carbons, note, 371 Potential Required to Pro- duce Spark between Point and Plate, 371 Potential Required to Pro. duce Spark between Two Metallic Balls, 370 Potential, Static and Cur- rent Methods of Measur- ing, Compared, 125 Potential, Sub-dividing into Known Fractions, 278 Potential, Unit of, 89, 141 Potential, Variation o^, with Resistance of (Jiven Volt- meter to Produce Givon Deflection, 41? Differences between Electric Poten- tial and Pressure of Water Flowing in. a Pipe, 83 Differential Galvanometer, Best Be* sistanoe for, 436 — Galvanometar, Construction o<s 140 of of of of of of of of of of of of of of of of of of of 496 PBAOTIGAL ELBCTRICITT. DUferentlal OalTftnometer, Latimer dark's, 150 Galvanometer, Mode of Ad- Jnetioflr, 150 <^— Galvanometer, Principle of, 148 — QaJLvanometer, Saperiority of Wbeatstone's Bridge over, 171 Galranometer, Uee ol Shnnte with, 183 Dilate Sniphurio Acid, EiTeot of ElectrolysiB of, 15 Diminution of Resistanee of In- ralaton with Increaae ol Temperatore, 271 Direet Comparison with Tangent Galvanometer, Gab'brating Galvanometer by, 58 Heading Qalvanome^rs, 76 Beading, Shielded, Dead-Beat Galvanometere, Advant- ageeof, 78 Dixeotion of Coirent, Definition of, U ——of Current in Add, Copper, and Zine Toltameters, ii — — of Current in Hagni^ring Spring Ammeteraand v olt> meters. Indication of, 388 — of Current round Uagnet. Conneolioin betweeu, and Poles produced, 17 of Flow of ElecMo Current, What is Meant by, 8 — of Magnetic Force jnrodnoed by Current in Flat Coil, Disadvantage of Msgnifying Spring Ammeter and Voltmeter, 391 Disadvantsges of Caidew's Volt- meter, S8S — of Cunyngfasme's Ammeter and Voltmi^er, 427 — of Electro • Magnetio Control Metera, 385 ^— of Gravity Control Meters^ ^-^ <rf Permanent Msgnet Meters, 376 of Siemens' Eiaetro-dynomoaa^ tor, 381 of Thomson's Large Current Galvanometer, 54 Discharge, Brush. 309 <— Glow, nioU, 360 ——Multiplying Power of Shunt used in Mesamring, 340 Dispersion Photometer, 454 Distance Spark can be sent between Balls of Inflnsnoe Machine, 871 Difltinetion between CondnetiCB and Induction, 07 between Galvanometer and Galvaaoficope, not*. 21 Distribution of Magnetism in Per- manent Magnet, H>*aanr- ing, 24 of Power in a Circuit, 445 Disturbanoe, Magnetic, ffiuelding Galvanometers from Ez- tmneous, 73 Drawing Curves on Squared Paper, 81 Curves to Correct Basalts ol Experiments, 34 Dry Pile, 372 Duplex Telegrsph^, Beaistsaee Boxes used in, 180 l^ynamometer, Messuring Currents with Siemens' Electro-, 379 —— Stemfflis' Electro-, 377. (8m also Siemens' Eleotro-I^ynamo- meter.) E 1?ABTH, Potential of, Arbitrsrily -^ taken as Non-fat, 84 Earth's Magnetic Force, Definition of the Horizontal Compo- nent of, nMe, 55 IHiMmite Eleetrophorus for giving Negative Charges, 8f» — • Eleetrophorus for giving Posi- tive Charges, 857 ^^^'^ Corrugating Sides of, •— Pillars, Common Fault in Con- stmotinff, 272 Seeostsnoe ol, S71 — — Specific Inductive Capacity of, SIO Edelmann's Electrometer, Sug- gested Improvements in, 134 — — Modification of lliomsoD's Quadrant Eleetrometer, 130 Effect of Electrolysis of Dilute Sul- phnrio Acid, 15 BIBaency Increases with Power in Electric Lamps, 458 of Arc Light, Measuring, 455 — — of Current Generator, Defini- tion of, 451 -^ol Electric Light, Measuring, 452 of Incandescent Lamps, 488 Elastic Curve, Definition of, 34 Eleotrie and Heat Conductivities, Comparison of, 156 ApparatniB, Stafic, should be En- fliosed in MetallioOMSb 108 IKBBZ. 497 Btoetric Are, DascripUon of, 188, 454 Are, Measuring IllnmixuttiDg Power of, in any Plane, 457 — Are, Potential Difference Re- qnired to maintain, be- tween Two Carbons, no(f, S71 Cbarge, 100. (S«« Charge.) Circnit, Work done in, 199 — • Condnctivity Diminishes more Kapidly thai Heat Con- duotlTitT, 159 Cnrrent. (Sm Current.) -^— Denfdtj. (8«€ Density.) Energy. {3f Enetgy.) Lamps, Description of Aro and lucandescent, 454 Lamps. Efficiency of. Increasing with Power, 458 ~— Light, Measuring Efflcieney of, 452 Potential. (8m Potential.) QoADtity. (See Quantity.) Sparks. (See Sparks.) Electrical Machines, FrictionaL (5m Machines.) *— - M'M^hinfHi, Influenoe, (Sm Ma- chines.) ^— Unita, Ohm only one jet Legalised, 140 Electricity at Best Besides only on Surface of Conductor, 119 -*-> Com]Hiring (Quantities of, Qal- Tanometncally, 299 Comparing Quantities of. Stati- cally, in (Condensers not Stores of, but of Electric Energy. 322 —•Measuring Quantity of, Abso- lutely, 2»9 Positive and Negative, 85 — — Potential of (k>uductor Depends imrtly on Amount of, 119 Quantity of. Defined, 109 Unit of (Quantity of, 289 <— — ()aantitj of, produced by Bub- bing Two Bodies together, 115 Bleotriflcation, Amount of a Body's, 109 ——Exterior, No Force inside Closed Hollow O>nductor One to, 99 — — Object of Bubbing Two Bodies together to prodnce, 115 Electro - Dynamometer, Siemens'. 377. {S«4 also Siemens Electro-Dyxuimometer . ) Electrode, Definition of, not«, 131 Elecux>lyBis, Effect of. of Dilute Sulphuric Acid, 15 Electro-Magnet, Description olt 6 O Q Eleotro-Msgoet, Strcogth of, whea Core is Slightly Mag. netised, 882 — - Msgnet, Saturation of, 388 — — Magnetic Control Meters, 392 Magnetic Control Meters, Ad- ran tagos of, 39 i — — Magnetic O>ntrol Meters. Crompton and Kapp's, 392 — — Magnetic Control Meters, Dts advantages of, 884 — Magnetic O>ntrol Meters, Paterson and CJooper'e, 393 Eleotrometer, Edelmann's Modiil- cation of Thomson's, 130 — - Suggested Improvements m Edelmann's, 134 — Use of, for proving Ohm's Law, IM Bough, 94 — — Thomson's Absolute, Portable, and (Quadrant, 93 '-— Weight, Lecture-room Model of, 88 Onard Bing for Weight, 89 —^ Weight, Increasing Sensibility of, by using Auxiliary High Potential, 91 Electromotive Force, Definition of, 20t Force, Constancy ci, in DanieU's Cell, 818 — Force, Measuring Besistanoe Containing, 409 ——Force of Oil Independent of its Size and Shape, 211, 23G Force of Bunsen's Cell, 220 Force of Daniell's Cell, 211 Force of Qrove's (^11, 218 Force of Leclanchtf Cell, 222 Force of Latimer Clark's CelL 411 — Force of Latimer Clark's Cell, Variation of, with Tempera* tore. 411 Force of Standard Daniell's C;eU,412 Force of Cells in Parallel, 241 Force of Cells in Series, 241 '— Force of Cells partly in Series and partly in ParaUeL 241 Force UsedbyDepres in Trans- mitting Power 37 Miles, 452 — — Forces of Batteries, Compari- son of, by obserrirg Hesist- ance through which they send Equal Currents, 231 — — > Force o( Batteries, Comparison of, by observing their Joint anil Opposed (torrents, 288 498 PRACnCAL BLBCTKICITT. £lMtxoinotiT9 IVmnm of Ciuivut Oflocnton. Condenser Method of Comparing, 841 Foroe, Meunring, 224 Electiioiihorlo Action, Compoand Interact Lew of. 361—372 Electrophonu, Aotion of, 360 Bertwsh'a BoUtory, 361 Deeeription of, 356 — Ebonite, givinf Negatire ChargeB,350 — Ebonite, lOTii^ PoaitiTe Cban»a,357 ElectitMoope, Calibrating Gold-Leof , 354 Condensing, 8B2 -~- Oold-Lcef , Improred Form of, M ^— Indicates Potential Diifereboea 95 -~- Yamishing Shade of Ordinazj Gold Leaf, 97 Eleotroeoopes, Obieetions to Ordi- nary Gold-Leaf, 96 Element, Simple Yoltaac, 209 E. X. F., Meaning of, 204. (Sm also ElectromotiTe Force.) Enclosure oi Statio Electric Appa- ratna in Metallio Case Neoeasary, 106 Condensera Stoics of Else- trie, 322 Produced by Frictional Elec- trical Machine, S.'H — Waste of, in Yoltmeters with High Eztemal Besistance, 422 EqniTalent of Heat, Mechanical, 901 Error in Ammeters on Berersi^ the Current, Testing for, 402 ^— . in Ammeters Produced by Ex* temal Magnetic Disturb- ance. Testing for, 408 *— in Ammeters Produced by Be- sidnal Magnetinn, Testing for, 400 — — in Ammeters Produced by Time, Testing for, 407 Testing Yoltmeters for Heat- ing, 415 Errors in Yoltmeters, Different Kinds of, 407 -^ in Wattmeters, 415 Examples : L. 12 ; ii. — vii., 13 ; viti., 14 ; uc, X., 52 ; n., 53 ; xii. xiiL,55: xiv.,56; xr., zvi, 67; XTii., 80; xviiL, xix., 90; XX., 01; xxi.— zziv., 14S| XXV., 143; xxx'i.— xxyiiL, 155; xxix., 156; xn.— xxxiii., 156; xxxiT., r.— xxxtII., 163; xxxTiii.— xl., UO: ^L^ xliiL, 201 ; xBt^ S» : x1t« 206; xItL— xUx., »7; L, 11., 227; lit, liu.. 228: Ut^ 232; It.— Ivil,2S3; Ituo.— Ix., 242; Ixi., 243; Ixii.. 247 ; Lull., IxiT., 246 ; Ixr.. 249; hirl, 250; Ixrfi.— Ixix., 2S8; Ixx., Ixxi^ 255; Ixxii, Ixxiii., 256; lxxtr.« 2S0; IzxT., 260; Ixxri.. 262 ; IxxviL, 263 ; hcxriu., 264; Ixxix., Ixxx., 9SS; IxxxL, 280 ; ^'«'*^*. — uxxfr^ 281; IxxxT., 294; Ixxxri., IxxxTii., 266 ; IxxxTiiL, 297 ; Ixxxix. — xcL, 996 : xciL, 311 ; xciii.— xer., 812 ; xcvi^ xovii., 313; xcriiL, xcix^ 323; o., 325; oi., 326; eii., 341; ciiL, 350; CtT., 437; CT.j CTi., 436; eriL, 499; cviii., cix., 440; ex., exi^ 443 ; cxii., cxiiL, 444 ; cxir^ 446 ; CXT., cxri., 417 ; cxriL. cxriii., 459; exix.» 460; cxx., 4t7l ; exxi., 473 ; exxii.^ 474 : cxxia., 475 Examples showing Diffearenoe be- tween Eleetrie Potentisl, Density, and Quantity. 121 Explanation of Eleotno dancing, note, 356 External Besistance, Yaiiation of, with Current and Potoa- tial Difference at Battery Terminals, 204 EquaU^ of Charges on Two Bodies obtained by Bubhing tliem together, 115 'pABADAY*S Eneriment onFloroe *■ in Cloeed Conductor due to Exterior Eleotriflcation, 99 Farad, Definition of the, 807 Fault, Common, in Constructing Ebonite Pfflsrs, 279 Fibre and Pivot Suspensions, 90 Suspension used in Thomson's Marine GalTanometer, 60 Field, Uniform Msgnetic, 86 Finding Angles from their Tangents Tangents from their Angles with Squared Paper; 57 -— the Maximum for an Expres- sion by means of Curve. 941 Fixed E. M. F. and BesistaaoeL Cuiw lent Derdoping Maximao INDEX. 499 Useful Power with Gene- rator with, 448 Fixed Bemstwice, Amugement of Cells nving Mnximum Useful Power to Conduo- tor with, 450 Flat Coil, Direction of Magnetio Force produced bjr Cur- rent flowing in, 43 Fleming^s Standard Darnell's Cell, 412 Flint Qlass, Besistanoe of, 271 Spedflo IndactiTe Capacity of, 310 Flow, Wiiat is meant by Direction of, of Electric Cnrrent, 2 of Electric Current compared with that of Water, 8, 80 Focal Length of Lens, Definition of, 456 F<Mroe, AttractiTe, between Two Plane Cunductors, For- mula Connecting, with Potential Difference and Distance between them, 87 Definition of Lines of, 43 — - Definition of Horizontal Com- ponent of Earth's Mag- netic, nat»t 55 — — Direction of Magnetic, pro- duced by Cnrreut flowing iaFbitCoil,43 — Electromotiye. {8m Electro- motive Force.) — — None Inside Closed Hollow Conductor duo to Exterior ElectriflcatioD, 9J Foster's, Prof. O. C, Simplification of Sine Oalvauometer, 61 Frietional Electrical Machines, 352 Electrical Macbines, Con- densers for use with, 313 Fulfilment of Conditions for I'an- gent Law in Tsngent Gal- vanometer, 43 G fiAljYA^flG Cells, 209. (ftcalso ^ Cells.) Jalvanometer, Definition of, 21 - — Compared with Ghilvanoscope, tiotf, 21 Constant of, 278 — — Absolute, 57 ^— - Astatic, Advantage of Putting Mirror Outaide Coils, 281 Astatic, Definition of, 282 Antatic, Thomson's, 2BS — — Astatic, Modified Thomson's, 284 •— Astatio, Mather's, 299 Oalvanometer, Astatic, Mudford's. 105 ——Astatic, Damping of Vibnu tions of Needle of, 284, 300 Ballistic, 292 — — Ballistic, Siemens' and Halske'a Galvanometer Used as, 29J Dead.Beat. 78 Delicate, 281 Delicate, Importance of being Well Insulated, 286 — Delicate, Necessity for Many Convolutions of Wire, 281 DilTexential, Principlti of, 148 Differential Construction of, 148 Differential,LatimerCUrk'8,150 •^—Differential, Best Resistance for, 436 — — Differential, Inferiority of, to Wheatstone's Bridire, 171 Differentia], Mode of Adjust- ing, 150 -^— Diflbreiitial, Use of Shunts with, 183 Direct-Beading, 76 Direct- Beading, Adju^meut to make, 75. 78, 385, 389 Large Current. Advantage of Low Besistance for, 136 Large Current, Deurez's, 69 — ^ Large Cnrrent, Electro-Mag- netic Control, aOi — :- Large Current-Gravity Control, V 891 Large Current, Msgnifying Spring, 386 Large Current, Permanent Mag- net Proportional, 75 '—- Large Current, Thomson's Per- ujaneut Magnet, 53 ——Large Current, Spring Con- trol, 377 Marine, 103 Marine, Fibre Suspension for, 108 Marine, Shielding, from Mag- netic Disturbaiico, 103 — — Portable, with Approximnte Absolnte Calibration, 69, 71 Potential Difference, 126 Potential Difference. El* ctxo- Moffnetio Coutrol, :I92 — — Potential Difference, Gravity Control, 391 ~- Potential Difference, Masrnify- iu^ Spring, 886 Potential Difference.Permanent Magnet Proportioual. 75 ^>— Poteutml Differeucti, Spring Control. 382 — — Potential Difference, Long Fine Wire used in. 1^ 500 FRAcncAL KLEcnticmr. RalTaaooictcr, Pot«Btal Differmop, wbcB it woMj be Em^ojed, 127 Pofcental IMItecnoe, Testing. 407 ——Proportional, 71 *— Proportioaal, with Pemuuftent ma^oei Control, 73 ' Proport onsl, with cniionii ControUioff Field. 72 Qnantity, Mather's Simple Form of, 299 Beflectw?, Iu3, 281, 298, 299 Kedecting, Defleetaon Proptr* tional to CorreDt with. 106 — Eeflecting, Kode of DaiivIieiiB with, 10> ^~— Reflecting. Iiampe for, 106 Eeflectii.g, Mirror for. 105 BeOecting. Mather's Form of, 299 Rdl«>ctiiig, Mndford'a Form of. 2H4 B«flectni8, Spirit Level for, 285 f in**, a2 Sine. Foeter^a Simpliflmtion of, 61 Shielded, 57. 73. 103, 390 Tangent, 38 Tangent, Simple Form of, 27 TasgentUdj ustment of Coil of. 46 Tangent, Best Deflection to IJae with. 41 — Tangent, Conditions that a Galvanometer may be, 96 ^— Tangent. Conditions of Tan- gent Law Fulfilled in, 48 Tangent, 0>ntrolled Only by £artb 's Magnetism. Vahies ill Amperes of Deflections of. 55 ^— Tangent, Proportions of Chan- nel in Bobbin of, when Tangent Law is Most Ao- cumtelj Ful ailed, 51 '^— Tangent, Scale for, 38 -^Tangent, Sensibility <^, Alter- i"g» hy Removing Needle from ilane of CoU, 52 — Tangent, Sensibility of, Al- t'-red br Varying Number of Windings or Diaaeter of Bobbin, 48 Calibrating. Relatively or Abso- lutely, 22, 27, 395-4 ;0 Calibrating, by Comparison with Tangent Galvano- meter, 68 Calibrating, by Sine Method. 64 Calibrating, by Sine Method in Higher Parts of Scale. 65 GalvUMMseCsr. Oafifaniiag, by Method with ~ Cuiieut, 67 by _ and Cell of Constant £.M. P.. S38 Califarating, by using Known Reaistsnons and Constant Potential Diff erenoe. 164 Calibimtion of, Unaifected hy Change in Strength ai Poles of 8iz»le Needle. 23 SensibilHj of* Incrsaaing, hy Diminishing Diameter of Wire need m Winding. 22 Sensibility of. Modes ot Yary- ing. 29 Sensifailily of .Yariation of, with Length of Mire Ueed in Winding. 418 SeoaihilityM. Variation of, with Reeistaaoe, 416 B^naibiUty of, Shnntii« to Diminish, 229 Sensihility of Tangent., Varia- tion of, 48 for Wheatstone's Bridge. Best Arrangement o^ aind Bat- tery, 171, 467 for Wheatstone's Bridge, Best Gange of Wire for, 172. 466 for Wheatstone's Bridge, Cur- rent thronirh, 4K5 <— — for Wheatstone's Bridge, Mean- ing of Deflection oC, 176 Apparent Increase of Resist- anoe of. Due to Damping. 319 Best Besistanoe to give to, 485 Coils, Rate of Prodaciion of Heat in. 419 Method of Measuring Reai«t- anoe by Loss of Charge. 348 — - Shielding, from Ertraneons Magnetic Disturbanoe. 57, 737108. 3J0 — — in fUmpIe Circn«t, Best ar ^ for, 435 and Shunt. C<nubined ance of. 178 Soft Iron Core Used in, 73 Use of Mirror witli, to Avoid Parallax, 28 and Voltameter. Relative Ad- vantakos of, 20 (Galvanometer. (Set also Ammeter 'Electro - Dynamometer Voltmeter.} Qalvanospope. Deflmtion of, nol«. 21 Description of, 6 Qas-Bumer, Albo-Carbon, for Gal- vanometera, nets, 106 IKDEZ. 501 Bc^eneratiTe* for Qnl- YanoRieters, 106 Generated in Yoltameter Inde- Stndentof Shape, Sise, aud istanoe of Plates, 10 Bate of Produotion in Sul- phuric Acid Voltametar by One Ampere, 12 GoBes, Differtfnoe of Preflsure Com- pared with Difference of Potential. 88, 121 Specific IndactiTe Capacity of, 310 Gearing', Ammeters and Voltmeters with Magnifying, 386 Generation of Heat by Eleotrio Cur- rent, 193 Generator, Current, Definition of Efficiency of, 451 Cnrreut, Measurement of £. M. F. of, 23^.231,231, Sil Current, Measurement of Be- Bistonoe of, 205, 225. 342 Current, Power Wasted in Heating, 445 Current, Work done by, 202 Current, with Fixed li. M. F. and Besistance, Current Developing Mazimnm Use* fnl Power with, 448 Generators, Current, Forms of. 206. (Sm also Cell, Batteries.) Gemum Silver, Change of Besist- ance of, with Temperature, 160 — Silver, Besistance of, for Given Length and Diameter, and for Giveo Length and Weight, 157 — ~ Silver, Besistance of, per Cubic Centimetre and per Cubic Inch. 154 Silver, Whv Bes'stance Coils are mode of, 160 GiMss, Flint, Besistance of, 271 Glow Discharge, note, 369 Gold, Change of llesistauce of, with Temperature, 160 • Electric and Heat Conductivi- ties of, Compared, 150 Besistance jof, for Given Length and Diameter, and for Given Length and Weight, 157 Besistance or, per Cubic Centi- metre and per Cubic Inch, 154 Leaf Electroscope, 94 — Leaf Electroscope, Calibrating, 354 -—Leaf Electroscope, Objections to Ordinary, 96 Gk>ld-Leaf Electroscope, Varnishing Shade of Oraiuary, 97 Graduation of Ammeters, Test for Accuracy of, 3tf5 -— of Cunyngbame's Ammeter and Voltmeter, 385 of Voltmeters. Testing for Ac- curacy of, 408. (See also Calibratinjr.) Graphically Becording Besults of Ex|>eriment8, 30 Becordmg Besults, Value of, S3 Gravity Control Meters, 391 Daniell's CeU, 212 Grove's Cell. 218 Cell, Chemical Action in, 219 Cull, E. M. F. of, 218 Cell, Besistanoe of, 218 Guard King, 89 Tube, 375 Guttapercha, Besistance of, 271 Specific Inductive Capacity of, SIO TTEAT, Amount of. per Minute -^ Produced by Given Cur- rent flowing through Given Besistance, 199 '■— Amount of. Produced per Second in Coil by Constitnt Current. Constancy of, 197 and Electric Coudnctivities» Comparison of, 158 Conductivity Diminishes more Bapidly than Electric, 159 — — Evolution of, in Conductor, by Electric Current, 3 Generated by Electric Cur- rent, Amount of, 192 Measuring Current |»y Bate of Production of. 197 — — Mechanical Equivalent of, 201 Badiation, Conduction, and Convection of, note, 195 Bate of Production of, in Ghil- vanometer Coils, 419 Heating Error in Voltmeters Di- minished by Use of Outside Besistance, 421 Error, None in Cai dew's Volt- m*iter. 426 Error, Testing Voltmeters for, 415-422 Current Generator, Power Wasted in, 4(5 Property of Current, Practica] Uses of. 4 Hermetically Sealing, Definition of note, 20 High Besistanoes, Measuring, 277 503 PRACTICAL ELECTRICITY. 