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Re: dQ and dW



jmclean@chem.ucsd.edu wrote:

Rauber, Joel says:
.....

Another point which I'm uncomfortable with in the classroom. I too eschew
the use of Delta Q and W for the obvious reason; but in my calculus level
class I have to refer to dQ and dW, and I've previously in mechanics
emphasized that d(anything) is a small change in something. So I have to do
some fancy footwork here and say that dQ and dW only mean a small quantity
and not a change, I mention the words "inexact differential" as well (not
that I expect them to understand inexact differentials, but simply to
sensitize them to the use of terminology that they will see later.)
Comments or suggestions?


The Reif textbook from which I first learned this stuff in college uses dQ
and dW with a bar on the stem of the d's (just like for h-bar in quantum).
It explicitly explains that the plain d will be used for the differential
of a quantity, and the d-bar will be used for small amounts of something
which doesn't have an associated quantity. I don't know if I can claim to
be a typical student, but that made a big impression on me at the time.
Although I didn't really understand it until later, I was at least clear on
what the issue was.

--
--James McLean
jmclean@chem.ucsd.edu
post doc
UCSD

Zemansky uses the d-bar to denote an inexact differential. Sears uses a d'
for this.

Roger