Re: Magnetic N and S poles

[Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>]

Bob Sciamanda wrote:

> ... I have actually quoted [see below] from the smaller sized 1956
> edition (a third author - Stephenson - was added by then). I would
> appreciate hearing from any owner of the 1943 edition whether
> what I have quoted from the later edition incorporated any
>  changes from the 1943 printing.

Bob's quotations showed that the F=q*(v x B) formula was
used in the 3rd edition to define B. I am now looking into the
first edition of this book; it is very different in that respect.
The chapter on magnetostatics is before the chapter on
electrostatics. Here the unit of H, oersted, is defined as dyne
per unit pole.

In a later chapter the unit of I, ampere, is defined as the
current producing H=2*PI oersteds in the center of a loop
whose radius is 1 cm. B is defined as mu*H, where mu is
a dimensionless material constant. The force on a wire
f=B*I*L is derived from the Biot Savart Law by the way
Newton’s 3rd Law. (Force with which a current element
acts on a probe pole must be equal and oppsite of the force
with which the probe pole acts on the wire element.)

Does anybody have access to the second edition? If so
please tell us if H was also defined magnetostatically in
it. When was the 2nd edition published? How was B
defined in the first edition of Sears and Zemansky? When
was the first edition of this book published? We still do
not know which textbbok was the first to define B in
terms of Lorenz formula. The oldest date so far is 1956.

The authors (Lemon and Ference) were professors at
The University of Chicago. Their 1942 prefece about
how students learn is quite interesting.
Ludwik Kowalski
P.S.

I wrote:
> > I suspect that no introductory textbook published before 1945
> > defined B in terms of  Lorentz formula. But I may be wrong.

Bob Sciamanda responded:
> From "Analytical Experimental Physics", Lemon & Ference, 1943 :
> "We may thus state that a magnetic fluix density exists at a point
> whenever a force acts on a moving charged particle  [but not on a
> stationary particle] . . .
> If a charge of q coulombs is moving with a velocity of v m/sec at right
> angles to a flux density of B webers/m^2, then the moving charge
> experiences a force of f newtons at right angles to both B and v which is
> experimentally given by f = Bvq.  [This equation] is a defining equation
> for the flux density B."
>
> They go on to the general case f = qvBsin(theta).  The fictitious poles of
> magnets are introduced much later but they are not used to define B or H;
> nor is the inverse square law for poles ever uttered.
> This is an introductory "General Physics" text.