1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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/ PV diagram

  1. Nov 6, 2016 #1
    1. The problem statement, all variables and given/known data

    figure: http://www.chegg.com/homework-help/...ivides-p-v-diagram-regions-1-2-follo-q5905441

    The dot in Figure (b) represents the initial state of a gas, and the isotherm through the dot divides the p-V diagram into regions 1 and 2. For the following processes, determine whether the change ΔEint in the internal energy of the gas is positive, negative, or zero.

    (a) the gas moves up along the isotherm

    (b) the gas moves down along the isotherm

    (c) the gas moves to anywhere in region 1

    (d) the gas moves to anywhere in region 2

    1.ΔEint is positive
    2.ΔEint is negative
    3.ΔEint is zero

    2. Relevant equations

    curve of an isotherm is a hyperbola so as the hyperbola becomes closer to the center (0,0) at its inflection point the temperature decreases

    deltaE internal= 3/2 nRdelta T means as temperature increases deltaE positive and Vise Versa

    3. The attempt at a solution

    when moving on isotherm the delta Einternal will be zero since Einternal depends on the change of temperature the a and b will be zero (a,b =3)

    but while moving under the curve then we are getting a lesser temperature. the temperature decreases so delta E negative so c is negative (c= 2

    similarly for moving above the curve then d is positive (d=1)

    Is my answer correct?
    Last edited: Nov 6, 2016
  2. jcsd
  3. Nov 6, 2016 #2
    Yes, provided in a and b you are dealing with an ideal gas.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted