A Promenade Along Electrodynamics

Features

• Cover Type: Paperback with 126 pages
• Published by: Vales Lake Publishing May 9, 2003
• Written in: English
• ISBN 10 Number: 0971484511
• ISBN 13 Number: 978-0971484511
• Book Dimensions: 8 x 5.3 x 0.5 inches
• Weighs: 8 ounces

Product Description
A superhighway connects the elementary laws of electric and magnetic interactions to Maxwell’s laws of electrodynamics. Physicists usually take this fast track in their education. But there are also interesting byways, while not as rapid, where one encounters many interesting and gorgeous views that are not accessible from the main route.

In particular, there are views of the superhighway’s bridges that span some conceptual gaps. For example, what formula correctly describes the immeasurable force between moving charges? How does one reconcile the contradiction between the Biot-Savart/Lorentz force and Newton’s third law? Why did Maxwell praise Ampere’s work but ignore his force law? What must be added to Wilhelm Weber’s incomplete theory of 1848 so that it can predict electromagnetic radiation? Fukai’s Promenade guides us through this unfamiliar but intriguing terrain.

About The Author
Junichiro Fukai, an Associate Professor of Physics, has taught physics at Auburn University since 1974.

Born and raised in Japan, he graduated from Waseda University earning a Bachelor of Engineering degree. After working at Toshiba Corporation as an engineer for 3 years, he came to US and entered the University of Denver majoring in Physics and earned his M.S.

He then moved to the University of Tennessee where he earned his Ph.D. in theoretical plasma physics. After postdoctoral studies at the University of Tennessee and Yale University, he went to Auburn University. There he worked on theoretical and experimental studies on plasma instabilities. His interest moved to theoretical investigations of dielectric breakdown phenomena and developing a device to decompose toxic gases by an electric discharge.

At Auburn he has taught various physics at almost all levels. Meanwhile he has been interest in fundamental issues of electrodynamics, relativity, and quantum theory.

Reader Reviews
Review of "A Promenade Along Electrodynamics," by Junichiro Fukai (Vales Lake Publishing, Pueblo West, USA, 2003, ISBN: 0-9714845-1-1) Dr. Fukai of Auburn University published a remarkable book of 126 pages. It presents many interesting ideas related with electromagnetism not covered by normal textbooks. It is divided in 9 chapters which run as follows: Introduction, Forces Between Two Charges Moving with Constant Velocities, Comparison with Relativistic Treatment, Ampere's Force Law, High Speed Limit and Comparison with the Special Theory of Relativity, Scattering and Orbit Problem, A More General Theory - An Encounter with Weber's Force Law, Applications of Weber's Electrodynamics, The Propagation of Electrical Signals in Vacuum. It ends with an Epilogue and two Appendices including biographies of notable physicists in the 19th century, a good Bibliography and an Index. The book begins presenting Lorentz's force acting on a test charge in the presence of electric and magnetic fields. This is the standard formula of classical electromagnetism but has some problems of symmetry, lack of action and reaction, paradoxes which arise when we change frames of reference etc. Some of these aspects are presented in the introduction of the book. It is then followed by a new force formula to replace Lorentz's expression, which avoids these paradoxes. The new expression is compared with standard relativistic treatment for the interaction between moving charges. In Chapter 4 the author presents Ampere's force law between current elements. Only by this fact this book should be read by all specialists and students of electrodynamics. The reason is that Ampere's expression has been forgotten and is not to be found in most textbooks dealing with electrodynamics, which only present Grassmann's force (based on Biot-Savart's expression of the magnetic field of a current element and compatible with Lorentz's force). Despite this fact is should be remembered that Maxwell himself knew both expresssions for the force between current elements (those of Ampere and Grassmann). In his masterpiece, A Treatise on Electricity and Magnetism, Vol. 2, page 174, paragraph 527, Maxwell compared these expressions and concluded that Ampere's force is undoubtedly the best, since it made the forces on the two elements not only equal and opposite but in the straight line which joins them. Grassmann's force, on the other hand, does not comply with action and reaction (the same as regards Lorentz's force). In the next page, paragraph 528, Maxwell said that Ampere's force should always remain the cardinal formula of electrodynamics. Modern books dealing with electromagnetism have forgotten about this and present only Grassmann's problematic expression. Fukai suceeds in deriving Ampere's force from his own more basic expression which deals with the interaction between point charges. He also discusses Rutherfod scattering formula and the orbit problem for two charges interacting with one another. Chapters 7 and 8 are devoted to Weber's electrodynamics and applications of this fascinating theory which was proposed by Maxwell's contemporary Wilhelm Weber, who worked in Goettingen in collaboration with Carl Friedrich Gauss (the same Weber of the magnetic flux unit). Weber's force is an extension of Coulomb's expression including terms which depend on the relative velocity and acceleration between the interacting bodies. Weber introduced in his expression the fundamental constant c and was the first to measure it in collaboration with Kohlrausch, finding essentially the same value as light velocity in vacuum, indicating a connection between electrodynamics and optics. All of this was done before Maxwell and his electromanetic theory of light. Weber and Kirchhoff also suceeded in deriving the telegraphy equation for a disturbance propagating along a wire which predicted the propagation of the signal in wires of negligible resistance at light velocity, once more before Maxwell! All of this is almost unknown nowadays but is discussed at length in Fukai's fascinating work. He also extends this work for the propagation of electrical signals in vacuum by considering it as composed of pairs of positive and negative charges. Fukai's also shows in details the compatibility of Weber's force with Maxwell's equations (but not with Lorentz's force law). He presents some possible experimental tests to distinguish Weber's force from Lorentz's force with great clarity and giving orders of magnitude. I recommend strongly the careful reading of this book which can initiate a new revolution in electrodynamics. It has many new ideas and insights, is full of historical information, is rich in modern experimental and theoretical references. And above all, is non dogmatic, presenting the concepts for the reflection of the readers in clear form and inspiring contents. Andre Koch Torres Assis Institute of Physics State University of Campinas 13083-970 Campinas, Sao Paulo, Brazil Email: assis@ifi.unicamp.br Homepage: http://www.ifi.unicamp.br/~assis