Elementary Treatise on Electricity and Magnetism

In the use of mathematical reasoning, we have allowed ourselves a little more freedom than was used by M. Joubert. This has made it possible in several cases, notably in connection with alternating currents and self-induction, to give the full details of calculation where he was only able to state results.

As the book deals throughout with matters belonging to the common stock of scientific knowledge, no systematic attempt has been made to assign facts or theories to their respective discoverers or authors. In fact, authors' names occur very sparingly in the following pages. There is, therefore, the more reason why we should acknowledge here how much we have borrowed from Professor Rücker in Chapter XXX. ("Electrical Units").

We cannot but recognise that one result of the changes we have ventured to make in M. Joubert's book has been the sacrifice of much of the symmetry and unity of plan which so admirably distinguish the original work. We desire to acknowledge with warm thanks the readiness with which M. Joubert consented not only to our proposal to translate his book, but agreed beforehand to our making such changes in it as we might think desirable. We have availed ourselves so fully of this permission, that the responsibility for whatever defects or errors may be found in the book in its present shape must, in fairness, rest upon us.

G. C. F.

E. A.

8th November 1895.

PREFACE TO THE FIRST

FRENCH EDITION

My object in writing this book has been to give a simple but fairly complete exposition of the theory of electricity and of the most important practical applications connected with it. I have had in view a reader who is wishful, not only to know facts, but to understand their logical interdependence, and to acquire accurate ideas of the essential nature of electrical phenomena. I have not supposed my reader to possess more special knowledge than what goes with an elementary classical education.

I have confined myself carefully to the region of facts, and have avoided all hypotheses. I have likewise avoided historical details. Interesting and profitable as I conceive these to be for those who know the facts of science, they are, in my opinion, of little use to beginners, and it is to these that my book is addressed.

J. J.

15th June 1888.

TABLE OF CONTENTS

CHAPTER I.

FUNDAMENTAL PHENOMENA.

3. Good

7. The

1. Electrification by friction. 2. Electrification by contact.
and bad electrical conductors. 4. Insulators. 5. Two correlative
electrical states. 6. Electrification of various substances.
electric field. 8. Energy of an electric field. 9. Variation of elec-
tric force with distance-Law of inverse squares. 10. Quantity of
electricity-Unit of electricity. II. Seat of electric energy

PAGE

1-15

CHAPTER II.

DISTRIBUTION OF ELECTRICITY.

12. Electric density. 13. Gold-leaf electroscope-Proof plane. 14. The

charge of a conductor in electrical equilibrium is purely super-

ficial. 15, 16. Faraday's ice-pail experiment. 17. Determination

of the electric density at different parts of an electrified conductor.

18. General conditions determining surface-density. 19. Electrifi-

cation of an isolated sphere - Electric force due to a sphere.

22. Electrification by induction. 23. Laws of

electrostatic induction. 24. Experimental verifications. 25. In-
ductive action in bad conductors. 26. Conducting sphere in a
uniform field. 27. Attraction of light bodies. 28. Inductive action
on the gold-leaf electroscope. 29. The electrophorus

29-42

CHAPTER IV.

ELECTRICAL POTENTIAL.

30. Conditions of electrical equilibrium. 31. Electric potential. 32.

Electric force and potential. 33. Equipotential surfaces. 34. Work

done by electric force. 35. Difference of potential defined in terms

of electrical work. 36. Difference of potential as depending on

electric charge. 37. Potential due to several charges. 38. Poten-

tial of an isolated sphere. 39. Units of measurement

PAGE

43-55

CHAPTER V.