Re: Energy, etc

[William Beaty <billb@ESKIMO.COM>]

On Tue, 10 Aug 1999, Ludwik Kowalski wrote:

> I will continue following traditional approaches but try to avoid terms
> which can later create problems, such as "amount of energy" or "energy
> transfer". What should we do with the idea that "one form of energy can
> turn into another"? Is this also a possible trap?


I regret that I've been unable to participate in the ongoing "energy
misconception" thread.

Here's a contribution (I don't know if I'll be able to respond at length
to replies) :

"Electric charge is substance-like" is a concept which can be used as a
very powerful mental tool.  Those who possess this tool can understand
many things which remain obscure to those who lack it.

The concept "energy is substance-like" is similar.  For example, because I
recently came to view the Poynting vector field as depicting a flow of a
"stuff", I understand electrical physics far more than I once did.  By
provisionally accepting that "energy is a stuff", many things became very
clear to me which previously were not.

But is energy really substance-like?  Certainly, WITHIN CERTAIN LIMITS.
Perform work to charge a capacitor, move the capacitor across the room,
then use the capacitor to power a motor.  We have moved "work" across the
room.  It's a flow of energy, and can even be measured (watts =
joules/sec.)

Suppose that we argue that energy is just an abstract concept, that energy
does not really exist, and therefor we should never teach anyone that
energy is substance-like or that energy can flow or be transferred.  If we
do so, then we have removed a powerful tool from our student's mental
toolbox.  Now suppose we do the same with "mass".  Ban the word "mass"
because it describes an abstract concept, not a "stuff" which can move
around or be localized.  Now suppose we ban any mental models everywhere,
since they are JUST abstract concepts and are not real in the way that
rocks and stubbed toes are real.  From this point on we shall insist that
it's misleading to treat "mass" or "energy" as if they were a "stuff"
that can ever, even under LIMITED CIRCUMSTANCES, move from place to place.

I strongly believe that doing all of the above will cause students
significant harm.  I view it as the equivalent of destroying imperfect
tools in the quest for a perfect one.  Screwdrivers don't work as
wrenches, get rid of them!  A hammer cannot turn a screw, so ban its use!
Only a perfect tool which always works in all situations can be tolerated,
and we end up with no tools at all.

Is energy really like a stuff?  I now see clearly: this question is a
distraction. The "energy is a stuff" concept is incredibly useful.  No,
being useful does not make it real.  Being useful makes it *useful*.

I've decided to take "heat" out of the wastebasket and put it back in my
toolbox.  There certainly was nothing else like it, and I missed being
able to use it.  Yes, its handle has dangerous splinters.  Yes, when I
used it incorrectly (used it to analyze chemistry,) I just made a big
mess.  I'll have to learn just where it can and cannot be applied, and
just how to hold onto it in order to avoid hurting myself.  If I want to
give it to another person, I'll have to train them in its proper and
improper use. Maybe I'll figure out a way to wrap all of the dangerous
parts with black electrical tape!

:)


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