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!

Homework Help: PV diagram problem

  1. Dec 12, 2014 #1
    1. The problem statement, all variables and given/known data

    A reversible engine contains 0.20 mol of ideal monatomic gas, initially at 600 K and confined to 2.0 L. The gas undergoes the following cycle:
    Isothermal expansion to 4.0 L.
    Isovolumic cooling to 300 K.
    Isothermal compression to 2.0 L.
    Isovolumic heating to 600 K.

    Calculate the net heat added during the cycle.

    I calculated heat add using Q=CvV(P1-P2)/R . I used that equation for two isovolumic process and got the difference
    I got 750j, it is wrong, why?

    Calculate the net work done during the cycle.

    I used W=nRT ln(V1/V2) for isothermal and P(V1-V2) for isothermal compression
    asd got the differnce. answer was 190 J again it wrong

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Dec 12, 2014 #2


    User Avatar

    Staff: Mentor

    You'll have to give more details of your calculations.
  4. Dec 12, 2014 #3

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    What is the change in internal energy over one complete cycle? What does that tell you about the relationship between net heat flow and work?

    Calculate the work done/on the gas in the isothermal expansion and compression parts and relate that to the net heat flow. Is work done during the isochoric heating and cooling?

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted