1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Thermodynamics: sign convention

  1. Mar 30, 2015 #1
    In physics book, if work is done by the system, it is positive
    in my chemistry book, if work is done by the system, it is taken as negetive.
    when I asked my chemistry teacher, he said the sign convention is different in physics and chemistry.
    but why are they different?
  2. jcsd
  3. Mar 30, 2015 #2
  4. Mar 30, 2015 #3
  5. Mar 30, 2015 #4


    User Avatar
    Science Advisor

    The convention of your physics book is not conventional for theoretical physics, however, it is often used in engineering thermodynamics.
    In physics and chemistry, one considers the change of the internal energy of the system. So if work is done on the system, work is counted positive.
    Same for heat, which is positive if heat is entering the system. On the other hand enigneers are usually interested in the work done by an engine when some heat is input.
    Hence they use different sign for work and heat.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Thermodynamics: sign convention
  1. Sign conventions (Replies: 4)