# Electricity for public schools and colleges

Longmans, Green, & co., 1893 - 451 ページ

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### 目次

 Polarity 2 Molecular Theory of Magnetism 3 Induction General Phenomena 7 Use of Keepers 9 Methods of Magnetisation 10 MECHANICAL AND MAGNETIC UNITS 1 Introductory 12 Velocity and Acceleration 13 Moments and Couples 14
 Resistance of a BatteryCell 230 Measurement of E M F 231 Electrometer Methods Open Circuit 232 Voltmeter Galvanometers 233 Method of Opposition 234 Table of Resistances in Ohms or 01 235 Table of E M F s in Volts 237 CHAPTER XV 238

 Magnetic Fields and Unit Field 15 Magnetic Moment of Practical not Ideal Magnets 16 Magnetic Curves 17 Magnetic Induction takes place along the Lines of Force 19 CHAPTER III 20 Use of Torsion Balance at constant angle 21 Method of Oscillations 24 SECTION PAGE 4 Laws of Magnetism 26 Proof of Law II by Torsion Balance 27 Measurements as affected by Induction 28 Compasses 29 Modification of Earths Lines of Force by the Presence of Iron Masses 30 Measurement of Declination 31 Resolution of Earths total Field into two or three Components 34 To find the Inclination or Dip 36 Measurement of the Earths Magnetic Elements 37 The Method of Deflexions 38 Magnetometers Changes in the Earths Field 40 CHAPTER IV 42 Dryness needed not High Temperature 43 Conductors and NonConductors 44 Electrics and NonElectrics 45 The two sorts of Electrification are always produced together 46 Equal Quantities of the opposite Electrifications are always pro duced simultaneously 47 The Fluid Theories of Electricity 48 The three Laws of Electrostatics 49 Law II The Force varies as Q x Q 51 First Ideas as to Induction 52 First Ideas as to Distribution 55 Faradays Icepail illustrating the Laws of Distribution and of Induction 57 Electrophorus 59 Frictional Electric Machines 60 Miscellaneous Experiments with the Electrical Machine 63 INTRODUCTORY CHAPTER ON POTENTIAL SECTION PAGE 1 Quantity of Electrification 65 Electrical Level or Electrical Potential 66 Measurement of differences of Electrical Level by Work 67 Elementary Ideas on Capacity 68 Lines of Force and Equipotential Surfaces 69 Induction from a Potential Point of View 70 Necessity of distinguishing Sign of Charge and Sign of Potential 74 CHAPTER VI 76 Experiments with the two Condenser Plates 78 Discussion of the Terms Bound and Free 82 An Isolated Body considered as the Limiting Case of a Condenser 83 Leyden Jars 85 The Unit Jar 86 Cascade arrangement of Leyden Jars 88 Nature of the Leyden Jar Charge 90 Various Effects of the Discharge 91 Induction Effects of the Discharge 94 Wheatstones Sparkboard 96 The Condensing Electroscope 98 CHAPTER VII 100 Application to Induction Machines 102 Varleys Induction Machine 103 Sir W Thomsons Replenisher 104 The Voss Machine 105 The Holtz Machine 108 CHAPTER VIII 113 Return Shocks 115 Potential at a Point in the Atmosphere 117 Methods of Measuring the Potential at a Point in the Atmosphere 118 Results of Observations 119 SheetLightning and other Phenomena 120 CHAPTER IX 121 Variation with Time 122 Faradays Method 124 Modern Methods 125 125 CHAPTER X 126 ELECTROSTATIC POTENTIAL 1 Introductory 127 Dimensions of Work 128 Work against a Constant Force 129 Potential and Difference of Potential 131 Equipotential Surfaces 133 Lines of Force are Perpendicular to Equipotential Surfaces 134 Fieldstrength and Rate of Change of Potential 135 The Mapping Out of Lines of Force Simple Case 136 General Case 137 Total Number of marked Lines of Force 138 Statement of some further Theorems on Lines of Force 139 The Potential of an Isolated Body 141 Capacity of an Isolated Sphere 142 Distribution from the Potential Point of View 143 Potential and Density distinguished 144 Important Case of a Spherical Condenser 145 The Plate Condenser 147 Formulae for Capacities c 148 Energy of Charging and Discharging 150 Examples in Energy of Discharge 151 Energy of Discharge in the Cascade Arrangement of Leyden Jars 152 Electroscopes and Electrometers 153 Sir William Thomsons Quadrant Electrometer 155 Uses of the Quadrant Electrometer 158 Examples in Energy of Discharge c 159 General Consideration of Electrostatic Fields of Force 161 CHAPTER XI 163 Galvanis Experiment 164 Voltas Experiments and Views 165 Voltas Pile from Voltas point of View 167 Voltas Cell and the Couronne des Tasses from Voltas point of View 169 The Contact and ChemicalTheories 170 Theory of the Simple Voltas Cell 171 Digression on the Galvanometer 173 173 Polarisation 175 175 Constant Batteries 176 Remarks on Cells and on Batteries 180 THE CHEMICAL PHENOMENA ACCOMPANYING THE PASSAGE OF THE CURRENT 1 Introductory 182 Chemical Effects General View 183 SECTION PACK 4 Grothiisss Hypothesis Nature of Electrolysis 186 Primary and Secondary Decompositions 188 Simultaneous Decompositions 189 Further on Faradays Laws of Electrolysis 190 Electrochemical Equivalents 191 Polarisation of the Electrodes 194 Secondary or StorageCells 196 Plantes SecondaryCell 197 Faures Accumulator 200 CHAPTER XIII 201 Statement of Ohms 203 Resistance further Discussed 4 The Exact Conditions on which Resistance Depends 204 Conductivity 206 Application of Ohms Law in a Simple Case 207 Graphic Representation of Ohms 209 Applications of the Graphic Method 9 Divided Circuits 211 Shunts 214 Fall of Potential through the Circuit 215 Kirchhoff s Two Laws 216 Maximum Current with a given Battery 201 20 204 204 200 207 209 211 211 214 215 2I 219 CHAPTER XIV 221 Resistance Coils and Resistance Boxes 222 Wheatstones Rheostat 224 Wheatstones Bridge General Principle 226 Slideform of Wheatstones Bridge 228 Wheatstones Bridge Resistance Box Form 229
 Units of Heat Work and Activity 239 Energy of the Electric Current 240 Joules Law 241 The Heating of Uniform Wires 243 Distribution of Heat in the Circuit 244 Heat Evolved with various Arrangements of n Cells 245 Case of no BackE M F in the Circuit 246 Numerical Examples 247 Failure of a Smees Cell to Decompose Water 248 Partial Polarisation in the foregoing Case 249 CHAPTER XVI 252 The Simple ThermoCell 253 The ThermoPile 254 ThermoElectric Powers 256 The Neutral Point 257 ThermoDiagrams 259 Peltier Effect Observed Facts 263 The Thomson Effect 264 Theory of the Simple ThermoCell 265 Theory of the Peltier and Thomson Effects 268 CHAPTER XVII 271 The + and Directions of the Lines of Force 273 Simple Form of Galvanometer 275 SECTION PAGE 5 The Tangent Galvanometer 276 The Sine Galvanometer 279 The Multiplying Galvanometer 280 The Controlling Magnet Method 282 Sir W Thomsons Mirror Galvanometer 283 The Differential Galvanometer 285 The Ballistic Galvanometer 286 Sir W Thomsons Graded Potential Galvanometer 289 Sir W Thomsons Graded Current Galvanometers 290 Webers ElectroDynamometer 291 Some General Observations on Galvanometers 292 Galvanometers for Practical or Commercial use 293 ACTIONS BETWEEN CURRENTS AND MAGNETIC POLES MAG NETIC EQUIVALENT OF A CURRENT ACTION BETWEEN CURRENTS A... 294 The Absolute System of ElectroMagnetic Units 297 Summary of ElectroMagnetic Units see 3 298 The Dimensions of the Derived Units 299 Field due to a Circular Current 302 Magnetic Potentials due to Magnetic Shells 304 Magnetic Equivalent of an Electric Circuit 306 This Equivalence is for the External Field only 307 Reaction of a Pole on an Element of Current 308 Action of a Pole on an Incomplete Circuit 310 Action of the Earths Field on Currents Completely or Partly Mobile 3ii 16 Actions between Currents Amperes Laws 311 Continuous Rotations of Currents 313 LAWS OF THE MOVEMENTS OF CURRENTS AS DEDUCED FROM THE CONSIDERATION OF MAGNETIC FIELDS AND POTENTIALS 1 M... 315 SECTION PAGE 3 Potentials on Poles and on Circuits 316 General Law of Movement of Magnetic Shells or of Electric Circuits 318 The Case of Incomplete Circuits 319 319 Reconsideration of Amperes Laws 321 Cases of Continuous Rotation 322 Potentials on Circuits 323 CHAPTER XX 324 Amperes Theory of Magnetism 326 Solenoid and Hollow Cylindrical Magnet Contrasted 327 Matter Placed in a Uniform Magnetic Field of Force 328 Movements of Small Bodies in a NonUniform Magnetic Field 330 A Long Body in a NonUniform Field 332 ElectroMagnets 333 Paramagnetic and Diamagnetic Phenomena 334 PseudoDiamagnetic Phenomena 335 Is there Absolute Diamagnetism? 336 Rotation of the Plane of Polarisation in a Magnetic Field 337 Other ElectroOptical Phenomena 340 CHAPTER XXI 342 General Account of Induction Phenomena 343 General Reason for Induced Currents 346 More Exact Reasoning in a Simple Case 347 General Expression for Induced E M 349 Induction where there is no Initial Current 351 Direction of the Induced Currents Lenzs 352 Constant Induced Currents 355 Changes that Give Induced Currents 357 Coefficient of Mutual Induction or of Mutual Potential PAGE 359 Selfinduction The Extra Current 360 Induced Currents of Higher Orders 362 CHAPTER XXII 363 Continuous Current Collected from Barlows Wheel 364 Induction in the Earths Field 366 Induction Coils General Plan 368 Practical Difficulties to be Overcome 369 Ruhmkorffs Coil 370 The Part Played by the Condenser 372 Condition of the Secondary Circuit when Closed 373 Secondary Circuit with AirBreak 374 Various Phenomena of the Secondary Discharge 376 High and Low Vacua 377 Discharge in High Vacua 379 CHAPTER XXIII 383 Clarks Machine 385 The Simple Commutator 386 Siemenss Armature 6 The SelfExciting Principle 7 Continuous Current Machines 387 TheGramme Construction of Armature 388 The Gramme The E M F s Induced in the Ring 390 The Gramme The Collecting Brushes 11 Curve of Potential Round the Collecting Axis 392 The Lead that Occurs when a Current is Running 393 SECTION PACE 16 Magneto Machines 395 SeparatelyExcited Machines 396 SeriesExcited Machines 397 ShuntDynamos 398 Other Methods of Winding 399 The Ferranti Alternate Current Machine 401 CHAPTER XXIV 402 SeriesDynamos as Motors 403 General Remarks on Dynamos and Motors 404 Formulae for Activity c Maximum Activity 405 Efficiency 408 S P Thompsons Diagrams 409 Electric Railways and TramCars Telpherage c 411 Distribution of Potential in the Circuit of a Dynamo and Motor 412 Work done per Second upon a Dynamo as Related to the Velocity v of Rotation 415 CHAPTER XXV 416 Telegraphic Alphabets 419 The Needle System of Telegraphy 420 The Morse System 421 Relays 422 Earth Currents Condenser System of Working 424 Insulation of Wires 426 Telephones Introductory 428 The Bell Telephone 429 Telephones with External Source of Current 431 Properties of Selenium The Photophone 432 General Account of Electric Lighting 433 The Incandescent Lamp 434 The Reverse E M F of the Arc 440 Voltmeters 446 Questions and Examples xxiii Answers to Questions xl 347 xlv 35i 352 355 357 xlvii 388 xlix 392 393 394 395 395 l

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Electricity for Public Schools and Colleges. By W. Larden. London ...
Electricity for Public Schools and Colleges. By W. Larden. London, Longmans, Green, & Co. 12°. sci 249, 237-237, 1887.
www.sciencemag.org/ cgi/ content/ citation/ ns-10/ 249/ 237-a