Re: [Phys-L] more about basic DC circuits

[John Denker <jsd@av8n.com>]

On 12/16/2013 11:31 AM, Philip Keller wrote:

>  I think we know the idea he was targeting -- the idea that resistors
> "use up" current. 

We agree that is a worthwhile target.  However, the ends do not justify
the means.  It is OK to replace one misconception with another.

> I think this sows how hard it is to write ANYTHING!  [and yes, i just saw
> the typo in that sentence, but I decided to leave it as evidence supporting
> the sentence :) ]

Yeah, writing is hard.  Writing books is really, really hard.

However, that does not mean it is OK to do a lousy job.

People manage to do hard things all the time, including things
a lot harder than this.  Think about how hard it is to make a
Lord of the Rings movie.  The process starts by realizing in
advance just how hard it is, and then arranging to properly
manage the task.  Proper management starts with allocating 
sufficient resources, among other things.

Books do *NOT* have to be full of errors.  The PSSC text has
very few serious physics errors.  The Feynman lectures have very 
few.  The first edition had scads of typos, but they didn't
affect the meaning ... and they have long since been fixed.

Please, let's not be fatalistic about this.  Please let's not
make excuses.  It is a tremendous disservice to students to ask
them to learn stuff that cannot possibly be true.  This is the
opposite and the enemy of critical thinking.  Getting the physics
right is a hard job -- for authors and teachers alike -- but it
is doable.

A good starting point is more cultural than technical:  It involves
creating an atmosphere where students are encouraged to come forward
with questions.  Students *do* notice things.  They notice that the
definition of alleged «conservation of current» is wildly inconsistent 
with the definition of conservation of momentum.  Not all of them
notice, but some of them do.  Oftentimes they cannot clearly articulate
the problem, but they can smell a rat.

The revolutionary idea is:  They don't have to put up with the rats.
And *we* don't have to put up with the rats.

I don't remember not being able to read.  I remember my mother teaching
me to /write/, but that came well after the reading.  And reading
chez nous did not just mean getting all the words;  we were expected 
think about it ... such as figuring out whether that big cat was telling
the truth or not.

I've been finding mistakes in science books since I was 6 years old.
It is an amusing sport.  It was encouraged at home.  It was definitely
not encouraged in school.  So I spent the next 10 years getting really
good at pretending to pay attention in class and pretending to not 
notice mistakes.  Going off to college was in some ways leaving home, 
but also the reverse, because college felt like home insofar as suddenly 
it was OK to be smart.  The prevalence of errors in the lessons went
down by orders of magnitude ... and also it was suddenly OK to ask about 
whatever bugs remained.

There is a well-known process for knocking the bugs out of things. I
haven't got time to describe the details, but it involves a lot of
teamwork, getting colleagues to critique an early draft, rewriting,
and iterating a bazillion times.  There is some nitpicking in this 
forum, but it is *nothing* compared to what you get if you recruit 
a few friendly colleagues who see it as their /job/ to spend hours,
days, or weeks polishing something.