1. Not finding help here? Sign up for a free 30min 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!

Determine ΔE, Q and W for the data in the Table

  1. Jan 29, 2013 #1
    1. The problem statement, all variables and given/known data
    The following table gives data, in KJ, for a system undergoing a power cycle consisting of four processes in series. Determine the a) missing table entries, each in KJ, and b) the thermal efficiency.

    I have attached an image of the Table.

    2. Relevant equations
    Q = (E2-E1) + W

    Q = ΔE + W


    3. The attempt at a solution

    I'm unsure whether a previous process affects the process that comes after it. Is it sufficient to use the formula that I've given to calculate the ΔE and W for processes 1-2, 3-4 and 4-1? If so, then how do I find the ΔE and W for process 2-3? Do I need to look at the process preceding it?

    Would I be right in saying that:
    W = 1200 for proces 1-2
    ΔE = 0 for process 3-4
    Q = 1000 for process 4-1
     

    Attached Files:

  2. jcsd
  3. Jan 29, 2013 #2
    The same formula applies to all 4 processes
    If it's cyclic, the sum of all four ΔE's must be zero.

    You were correct about the following:
    W = 1200 for proces 1-2
    ΔE = 0 for process 3-4

    But, you were wrong about Q = 1000 for process 4-1. Check your arithmetic.

    Since you know ΔE for 3 out of the four processes, you know it for the 4th because the sum of the ΔE's must be zero.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook