Re: Magnetic N and S poles

[Brian McInnes <bmcinnes@PNC.COM.AU>]

kowalskil at kowalskil@MAIL.MONTCLAIR.EDU wrote:

> When did the transition occur? Which introductory textbook
> was the first to use the Lorentz force law (F = q v cross B)
> as the definition of B?

Harnwell's book "Principles of Electricity and Electromagnetism" was first
published in 1938.  The copy in my possession is the second edition,
published in 1949, but careful reading of the Prefaces to both editions
indicates that no major changes to Harnwell's treatment of the theory of
magnetism.  Harnwell's approach is "from the point of view of the
electromagnetic phenomena associated with moving charges rather than from
that of permanent magnetism" (preface; 1st edition).  Then on page 301, 2nd
edition, he writes:" ..it is convenient to introduce a vector B, known as
the magnetic induction, which determines the force on a current element. The
element of induction is defined by the equation
 dF(sub1)  = i(sub1) cross dB(sub2) ".

Harnwell's book was one of the MacGraw-Hill International Series of Pure and
Applied Physics.  A glance through the books from this series listed on the
frontpiece page is a trip down memory lane.

Brian McInnes