Re: [Phys-L] prioritizing misconceptions

[John Denker <jsd@av8n.com>]

On 04/02/2014 05:48 PM, andre adler wrote:
> So the quote I posted, earlier in this thread, from the 13th edition of
> University Physics connecting Lenz's Law to conservation of energy is in
> error - perhaps a more serious concern as presumably far more students use
> that book in a course then might come across that question on a test.

Sure.  In this case, we have a widely-used book and an 
obscure test, so the book is more of a concern.

OTOH, if we were talking about a widely-used test and
an obscure book, the test would be more of a concern.

On the third hand, on any reasonable scale, there are 
vastly more serious things to worry about.  For starters,
the _University Physics_ book
 a) explains entropy in terms of "disorder", and then
 b) defines entropy in terms of dQ/T.

I reckon nobody is going to understand thermodynamics
in general -- including (!) the argument about the sign
that appears in Ohm's law and Lenz's law -- until they
unlearn both (a) and (b).

Seriously:
 A') Disorder (to the extent it can be defined at
  all) is a property of the microstate, whereas
  entropy is a property of the macrostate, a property
  of the distribution.  Specifically, it is an ensemble
  average of the surprisal.

 B') There is no such thing as dQ (except maybe in
  trivial cases).  As Thomas A. Moore so aptly put 
  it, dQ is a crime against the laws of mathematics.

There are some students who can learn by rote some of
the key results in thermodynamics, but even that is
an iffy proposition, and more importantly if you care
about /understanding/ then AFAICT you have to get rid
of "disorder" and "dQ".

As a separate issue, the book says there are two kinds
of electric charge (which is wrong) and credits Ben
Franklin for naming the two kinds (which adds insult
to injury).  Franklin rightly insisted there there is
only one kind of charge, and coined the names positive 
and negative for precisely this reason, to emphasize 
a difference in /amount/ ... not a difference in kind.

The book attributes to Einstein the "principle of
relativity" ... even though Galileo set forth the
principle with exquisite clarity more than 250 years
before Einstein came on the scene.  I'm not sure this
counts as wrong physics, but it is certainly wrong
history.  Physicists do not have a license to falsify
historical facts, just as historians do not have a 
license to falsify physical facts.  Besides, why
mention it at all, if you can't be bothered to get 
it correct?  This sort of thing is a huge disservice 
to students, because it gives them a false impression 
of how science is done.

The book proceeds to present a version of relativity
that has been obsolete for more than 100 years.  Again
I'm not sure this counts as "wrong" physics, strictly
speaking, but it is obsolete, more obsolete than a
penny-farthing bicycle, and it will all have to be
unlearned before there can be any hope of understanding
modern (post-1908) relativity, including general
relativity aka gravitation.

The book introduces Kirchhoff's "laws" without hinting 
that there might be any limitations to their validity 
... much less elucidating what the limitations actually
are.  This is a matter of some significance to premed 
students (among others), on rare occasions life-and-
death significance, because hospitals have lots of 
problems with ground loops, i.e. with circuits that 
violate Kirchhoff's laws.  Some hospitals forbid people
to carry cell phones ... not just to use them, but to
even carry them ... because they are tired of the
things messing up the heart monitors and other
instrumentation.  If there were more people who
understood the physics of the situation this would 
be much less of a problem.

You'd think that by the time they got around to the
13th edition they would fix some of the most glaring
errors.

===============

I have not reviewed this book in any detail.  I just
mentioned a few examples that I found with a few
minutes of effort.

Based on experience with other books of this size,
I would be willing to bet that this book contains
hundreds of errors, many of them far more serious
than anything having to do with Lenz's law.

Writing books is hard.  I reckon producing a really
good book would be comparable to producing a small
Hollywood movie.  The problem is, everybody including
publishers and authors wildly underestimate how hard
it is, so they try to get by with nowhere near enough
resources, and the quality of the product suffers
accordingly.

I consider this to be management malpractice on a
grand scale.