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J notation impedance

  1. Oct 27, 2011 #1
    1. The problem statement, all variables and given/known data

    We have a capacitor in parallel with an inductor. These are both in series with a resistor and capacitor.

    Calculate the J notation Impedance of the network. I only want the initial basic solution.

    The problem I have is that sometimes the J notation of C is -ve and sometimes +ve ?

    2. Relevant equations

    3. The attempt at a solution

    Product/sum of the parallel cct:

    jwL x 1/jwC/jwL*1/jwC This is the Inductor and capacitor impedance equation.

    The above will be added to:

    R -j(1/wC)

    My question is therefore, why in the above example at product over sum would it be ok to say jwL x 1/jwC/jwL*1/jwC i.e. * a +ve 1/jwC

    When below it I can add it to R and -j(1/wC)

    I hope this makes sence, thanks for any help in advance.
    Last edited: Oct 27, 2011
  2. jcsd
  3. Oct 27, 2011 #2


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    Science Advisor
    Homework Helper

    hi lubo! :smile:
    ah, but the first j is on the bottom, while the second is on the top …

    and -j = 1/j :wink:
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