New AP Physics Convention in Thermodynamics

[Jeff Weitz <weitz@PIPELINE.COM>]

Hi Everyone,

 

I certainly appreciate the intensity with which so many people respond to questions, and also the discussions that evolve from those questions.

 

The College Board has changed a sign convention in thermodynamics as follows:

"Another change for 2002 relates to the sign convention used for work in thermodynamics. In thermodynamic equations, the symbol W will represent the work done on a system rather than by a system, so that the first law of thermodynamics will be written D U = Q + W. This change makes the sign convention consistent with that used for work in mechanics, as well as with the thermodynamic convention used in most chemistry and some physics textbooks."

    -from http://www.collegeboard.org/ap/physics/html/cours014.html

 

Back in the stone ages, I was taught that W is positive when the gas does work, and I've taught it that way since.  Now, of course, I can change, though I do like to write Q = W + D U. 

What is the sense of the folks on this list? How widely is the new AP convention used as compared with the old one?

 

Hope summer is treating everyone well,

Jeff Weitz