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Homework Help: 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.
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