Isobaric Process - Sign Convention For Work

Sign Convention For Work

The motivation for the specific sign conventions of thermodynamics comes from early development of heat engines. When designing a heat engine, the goal is to have the system produce and deliver work output. The source of energy in a heat engine, is a heat input.

If the volume compresses (delta V = final volume - initial volume < 0), then W < 0. That is, during isobaric compression the gas does negative work, or the environment does positive work. Restated, the environment does positive work on the gas.

If the volume expands (delta V = final volume - initial volume > 0), then W > 0. That is, during isobaric expansion the gas does positive work, or equivalently, the environment does negative work. Restated, the gas does positive work on the environment.

If heat is added to the system, then Q > 0. That is, during isobaric expansion/heating, positive heat is added to the gas, or equivalently, the environment receives negative heat. Restated, the gas receives positive heat from the environment.

If the system rejects heat, then Q < 0. That is, during isobaric compression/cooling, negative heat is added to the gas, or equivalently, the environment receives positive heat. Restated, the environment receives positive heat from the gas.

Read more about this topic:  Isobaric Process

Famous quotes containing the words sign, convention and/or work:

    The symbolic view of things is a consequence of long absorption in images. Is sign language the real language of Paradise?
    Hugo Ball (1886–1927)

    “We’ll encounter opposition, won’t we, if we give women the same education that we give to men,” Socrates says to Galucon. “For then we’d have to let women ... exercise in the company of men. And we know how ridiculous that would seem.” ... Convention and habit are women’s enemies here, and reason their ally.
    Martha Nussbaum (b. 1947)

    My work is the only ground I’ve ever had to stand on. I seem to have a whole superstructure with no foundation—but I’m working on the foundation.
    Marilyn Monroe (1926–1962)