Voltage Division - AC cct.

Discussion in 'Homework Help' started by Ammar i, Feb 26, 2013.

  1. Ammar i

    Thread Starter New Member

    Feb 7, 2013
    4
    0
    Hi,
    We have this cut. :
    [​IMG]

    and in the image below, I10 is calculated by using current division :

    [​IMG]

    I tried to find it using voltage division but the answer is wrong :
    Vx(of the upper node) = 100 * \frac{j5}{4+j5} = 60.98 + j48.78 V

    => I10 = \frac{Vx}{10 - j5} = 2.93 + 6.34 = 6.98 \ 65.2

    which is wrong, WHY?

    thanks
     
    Last edited: Feb 26, 2013
  2. WBahn

    Moderator

    Mar 31, 2012
    17,769
    4,804
    What's your basis for this equation?

    Before you say, "It's the formula for a voltage divider," think about what a voltage divider is and where the formula for a voltage divider comes from.
     
  3. panic mode

    Senior Member

    Oct 10, 2011
    1,321
    304
    you need to define two impedances before you can use voltage divider
    Vx=Vin*Z2/(Z1+Z2)

    can you tell what are Z1 and Z2?
     
  4. WBahn

    Moderator

    Mar 31, 2012
    17,769
    4,804
    HINT: Z1 and Z2 have to be in series.
     
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