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!

Equivalent impedance

  1. Dec 9, 2007 #1
    hello I have a problem in calculating the equivalent impedance of a simple AC circuit, where the impedances are:

    Z1 = 5+i20
    Z2 = 5+i20
    Z3 = 10-i2,5
    Z4 = -i10
    Z5 = 5

    and I need to find:

    Z_eq = Z3 // [(Z1 // Z4) + (Z2 // Z5)]

    where the + indicates 2 components in serie and the // indicates 2 components in parallel.

    My calculations always bring me to

    but my book says Z_eq=28,33.

    Which is the correct eqv impedance?

    Thank you
    PS-I used the formula Za//Zb = (Za*Zb)/(Za+Zb)
    to calculate equivalent impedances of two components in parallel, and the sum for components in serie.
  2. jcsd
  3. Dec 10, 2007 #2
    Well, there's a mistake somewhere.

    If I use the values you gave for Z1 to Z5, I get the same result you did.

    However, if you set Z3 = 5 + i20, then you will get the result in the book.
  4. Dec 10, 2007 #3
    Ok then there probably is a mistake in the book because Z3 is in fact equal to 10-i2,5 as I calculated and as the book reports. Lost some time on this stupid mistake...

    Thank you very much for taking the time to verify this! :)

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?