Practical Electricity: A Laboratory and Lecture Course for First Year Students of Electrical Engineering, Based on the International Definitions of the Electrical Units, Volume 1

Front Cover
Cassell, limited, 1897 - Electricity - 643 pages
 

Contents

SECTION
53
Why a Galvanometer Needle has a Given Deflection for a Given Current 20 Mapping out Lines of Force 21 Comparing the Relative Strength of the ...
63
SECTION PAGE 24 Scale for a Tangent Galvanometer
87
Tangent Law
91
Variation of the Sensibility of a Tangent Galvanometer with the Number of Windings and with the Diameter of the Bobbin
95
Tangent Galvanometer
99
Values in Amperes of the Deflections of a Tangent Galvano meter controlled only by the Earths Magnetism
102
Magnetometer
107
Calibrating any Galvanometer by Direct Comparison with a Tangent Galvanometer
108
Pivot and Fibre Suspensions
110
Sine Law
111
Employment of the Sine Principle in Galvanometers
118
63
120
Construction of Galvanometers in which the Angular Deflec tion is directly Proportional to the Current
124
Galvanometers of Invariable Sensibility
127
67
130
69
132
71
135
Gravity Control Ammeters
138
Moving Coil Ammeters
144
Moving Coil Ammeter with Magnetic Control
150
CHAPTER III
152
79
158
and Negative Potentials
160
Electrometer
162
83
165
Ohms Law
167
Adjusting the Coil of a Tangent Galvanometer
169
Resistance
172
Ohm
173
Volt
174
Current Method of Comparing P Ds
176
Reason for Using High Resistance Galvanometers for P D
178
Voltmeter
179
Ammeters used as Voltmeters
181
Moving Coil Voltmeter
183
Voltmeters used as Ammeters
188
GoldLeaf Electroscope
191
Sensibility of GoldLeaf Electroscopes
194
No Force Inside a Closed Conductor Produced by Exterior Electrostatic Action
196
Potential due to Exterior Electrostatic Action is Uniform at all Points Inside a Closed Conductor
197
Voltmeters must be Enclosed in a Conducting Case
198
The Potential of a Conductor
200
CHAPTER IV
232
Resistance of Metals and Alloys for a Given Length
260
Conductors of Large Specific Resistance have Small Tem
267
Conductivity
274
Mode of Winding Resistance Coils and Gauge of Wire
280
CHAPTER V
313
Back E M
370
Distribution of Potential in a Battery
374
A Current Generator may Abstract Energy from a Circuit even when its E M F Helps the Current
381
3
385
Arrangement of Part of the External Circuit to Receive Maximum Power
393
Way in which Power Received by External Circuit Varies from Maximum
397
Efficiency
404
Efficiency of Electric Transmission of Energy
408
Connection between Electrical Efficiency of Transmission and Ratio of the Power Received to the Maximum Power Receivable
412
TYPES CONSTRUCTION CHEMICAL ACTION RELATIVE ADVANTAGES COST OF WORKING TESTING GROUPING SECTION PAGE 130 ...
418
TwoFluid Cell
423
Local or Prejudicial Action
428
Gravity Daniells Cells
431
Minottos Cell
433
Resistance of Daniells Cells
434
4
435
Groves Cell
438
Bunsens Cell
443
Potassium Bichromate Cell
445
Leclanché Cell
449
Dry Cells
457
Hellesen Dry Cell
458
Burnley or E C C Dry Cell
459
Obach Dry Cell
460
EdisonLalande Cell
462
Clarks Cell
466
Temperature Variation of the E M F of the Clarks Cell
475
Calculation of the E M F of a Cell from the Energy Liberated by the Chemical Action 148 Cost of Producing Electric Energy with Galvanic Cells and
477
with a Dynamo Compared
482
Measuring a Cells Resistance when Very Small
492
Measuring a Cells Resistance when Not Very Small
493
Remarks on the Preceding Methods of Measuring the Resistance of Cells
498
Comparing the Electromotive Forces of Cells
502
Poggendorffs Method of Comparing Electromotive Forces
507
Potentiometer Method of Testing the Accuracy of a Volt meter Scale
510
Fosters Method of Subdividing a Wire into Lengths having Equal Resistances
513
Potentiometer Method of Graduating a Voltmeter in terms of the E M F of a Clarks Cell
516
Use of a Clarks Cell and a Known Resistance as a Standard of Current
519
Calibrating a Galvanometer by using Known Resistances and a Čell of Constant E M F
521
Constant P D and Constant E M F
522
Independence of Currents in Parallel Circuits
525
Arrangements of Cells
536
Mercury Switchboard for Batteries
539
Arrangement of a Given Number of Cells to produce the Maximum Current through a Given External Resistance
545
Minimum Number of Cells Required to Produce a Given Current and P D
549
Arrangement of Circuit requiring the Minimum Number
555
APPENDICES
565

Other editions - View all

Common terms and phrases

Popular passages

Page 595 - As a unit of resistance, the international ohm, which is based upon the ohm, equal to 109 units of resistance of the Centimeter-Gramme-Second System of electro-magnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice 14-4521 grammes in mass, of a constant cross-sectional area, and of the length of 106-3 centimeters.
Page 595 - Ampere, which is one-tenth of the unit of current of the CGS system of electromagnetic units and which is represented sufficiently well for practical use by the unvarying current which, when passed through a solution of nitrate of silver in water, in accordance with a certain specification, deposits silver at the rate of 0.001118 of a gramme per second.
Page 601 - It is convenient to arrange the mounting so that the cell may be immersed in a water bath up to the level of, say, the upper surface of the cork. Its temperature can then be determined more accurately than is possible when the cell is in air. In using the cell sudden variations of temperature should as far as possible be avoided.
Page 596 - Victoria, by virtue of the power vested in Her by the said Act, by and with the advice of Her Privy Council, was pleased to approve the several denominations of standards set forth in the Schedule thereto as new denominations of standards for electrical measurement.
Page 25 - It is then rinsed successively with distilled water and absolute alcohol and dried in a hot-air bath at a temperature of about 160° C.
Page 599 - Materials. 1. The Mercury. — To secure purity it should be first treated with acid in the usual manner, and subsequently distilled in vacuo. 2. The Zinc. — Take a portion of a rod of pure redistilled zinc, solder to one end a piece...
Page 470 - ... acid. The crystals should be dissolved with the aid of gentle heat, but the temperature to which the solution is raised should not exceed 30° C.
Page 471 - Then insert the cork and zinc rod, passing the glass tube through the hole prepared for it. Push the cork gently down until its lower surface is nearly in contact with the liquid. The air will thus be nearly all expelled, and the cell should be left in this condition for at least 24 hours before sealing, which should be done as follows:— Melt some marine glue until it is fluid enough to pour by its own weight, and pour it into the test tube above the cork, using sufficient to cover completely the...
Page 598 - C. After cooling in a desiccator it is weighed again. The gain in weight gives the silver deposited. To find the current in amperes, this...
Page 470 - ... paste for an hour at this temperature, agitating it from time to time, then allow it to cool ; continue to shake it occasionally while it is cooling. Crystals of zinc sulphate should then be distinctly visible, and should be distributed throughout the mass ; if this is not the case, add more crystals from the stock bottle, and repeat the whole process. This method ensures the formation of a saturated solution of zinc and mercurous sulphates in water. To set up the Cell. The cell may conveniently...

Bibliographic information