As happens so often in science, important works of pioneers are overlooked, suppressed, poorly understood and therefore remain unknown to students and professionals. Prof. Andre Koch Torres de Assis of the University of Campinas in Brazil tells of such a case in his recent book, co-authored with Julio Akashi Hernandes. The works of two German scientists - Wilhelm Weber and Gustav Kirchhoff - on fields that form around current carrying wires, are detailed in a new book titled The Electric Force of a Current: Weber and the Surface Charges of Resistive Conductors Carrying Steady Currents.
The book is published by Apeiron, Montreal, it has 239 pages, the ISBN number is 978-0-9732911-5-5. The paperback edition is also available from Amazon.
A PDF of the book (5 MB) can be downloaded from Assis' webpage, and the cover is available there as well.
According to a message from Prof Andre Assis, the book is devoted to answer two main questions:
(A) Is there a force between a resistive wire carrying a steady current and an external point charge when they are at rest relative to one another? In particular, is there a component of this force which depends upon the voltage of the battery connected to the circuit? This first question can also be phrased as: A stationary and resistive wire carrying a steady current generates an external electric field?
(B) Is this wire neutral at its internal points and along its surface?
"In the first three Chapters we present the opinions of many eminent scientists as regards these questions. Then we present theoretical reasons and experimental results showing why the answer to the first question is affirmative and the answer to the second question is negative, contrary to many statements against these points of view. These first few Chapters should be of interest to most readers.
We then present many analytical calculations of this force and distribution of surface charges in important configurations of steady currents: (straight wire, coaxial cable, transmission line, solenoid, toroidal conductor). We compare the calculations with many experimental results.
We include two Appendices discussing the pioneering works of Wilhelm Weber and Gustav Kirchhoff. They showed the necessity of these surface charges in resistive wires carrying steady currents. Weber was the first to try to calculate their distribution for a straight wire and for a ring. At the end of the book we quote 259 references related to this topic.
I take this opportunity to inform that Weber’s main work in which he derived his force law from Ampere’s force between current elements is now available in English translation. This is only the first of a specific series of 8 large papers published by Weber, with the series dedicated to electromagnetic measurements. Weber’s force depends not only upon the distance between the interacting charges, but also upon their relative velocity and their relative acceleration. Complete English translation in PDF format (2.2 MB):
http://www.ifi.unicamp.br/~assis/Weber_1846.pdf
Weber’s work discussed in the Appendix quoted above is the second paper of this series."
Andre Koch Torres Assis
Clearly, this is not a book for all readers, but some of you may be interested in the specific problems it discusses.
Here is the book's foreword:
Continue reading "The Electric Force of a Current - 'Back to Basics' on Electromagnetism" »
