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Re: Magnetic N and S poles



Yes Ludwik, the first (1943) edition was an over-sized volume profuse with
large photographs. Alas, my copy has long since disappeared - borrowed
and never returned. I have actually quoted from the smaller sized 1956
edition (a third author - Stephenson - was added by then). I (and I'm
sure Ludwik) 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.

To your second question, the authors nowhere specify a college or
high-school market, but the free use of calculus would imply a college
course of the 1940's or 1950's.

I note in passing that this text introduces the momentum-impulse theorem
before the work-energy theorem.

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor
----- Original Message -----
From: "Ludwik Kowalski" <kowalskiL@MAIL.MONTCLAIR.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Sunday, December 16, 2001 4:18 PM
Subject: Re: Magnetic N and S poles


Thanks Bob; I was wrong about 1945. For the time being 1943
becomes the date for the first introductory physics textbook in
which B was defined in terms of Lorentz formula. But perhaps
somebody will report an older example. Was it a college or high
school textbook? I do recall seeing it somewhere (large pages?),
about three decades ago.
Ludwik Kowalski

Bob Sciamanda wrote:

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

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.