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I need a 2nd opinion on a circuit analysis answer

  1. Feb 1, 2007 #1
    1. The problem statement, all variables and given/known data
    Use superposition to find [tex]I_L[/tex]

    [​IMG]

    2. Relevant equations
    -The overall current is the sum of the currents supplied by each source individually


    3. The attempt at a solution

    for source B only (current source is open):

    ---ohm's law: [tex]\frac{100V}{15k + j25k} = 3.43mA( -59.04 degrees)[/tex]

    Here is where I'm having to defend my answer:

    for souce A only (voltage source shorted):

    ---since there is no phase shift labeled, it should be assumed that the current source can be treated as a DC source, treating the inductor as a short, making [tex]I_L[/tex] -20mA

    Is this wrong? Should I treat a current source as AC if it has other AC sources involved in the circuit? If this is so I'd just do a current divider to get [tex]I_L[/tex]
     
  2. jcsd
  3. Feb 1, 2007 #2
    I believe the question would have to be more explicit in defining whether the 20mA is an ac or dc source.
     
  4. Feb 1, 2007 #3
    Well no extra information was given than what's shown, yet I got it marked wrong for treating it one way over the other...

    Am I going to have to call out my professor again? I'm losing all my brownie points because of his dud test questions
     
  5. Feb 1, 2007 #4

    Gokul43201

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    I would imagine the "+" by the current source tells you it's a dc source.
     
  6. Feb 1, 2007 #5
    Well actually he graded it as it being an AC source.
     
  7. Feb 1, 2007 #6
    If you are answering the question as part of a test and if the professor is not available to clarify, then I guess you could always offer both solutions, one for each case.

    Failing that, then I suppose at the last resort you should treat it as ac since, as you said, there are other ac sources in the circuit.
     
  8. Feb 1, 2007 #7
    Hmm... but a "+" sign also appears beside the dependent voltage source and that one is clearly ac.
     
  9. Feb 1, 2007 #8

    Gokul43201

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    Haha! Yes, it does. What on earth is it for, then?
     
  10. Feb 1, 2007 #9
    For the dependent voltage source, I would imagine that it is there to indicate where the +terminal is (neccesary in defining voltage). I don't know why it appears beside the current source.
     
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