Electricity for public schools and colleges (Google eBook)

Front Cover
Longmans, Green, & co., 1893 - Science - 451 pages
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Contents

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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