Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Finding impedance in an ideal transformer circuit

  1. Dec 18, 2009 #1
    1. The problem statement, all variables and given/known data
    This is a review question for my test, but I can't get the right answer, the problem is to find the impedance ab.

    2. Relevant equations
    Zin = 1/a^2 * ZL

    3. The attempt at a solution
    The 10 ohm resistor and the capacitor are in parallel and then add the 50 ohm resistor times 1/9. Doing this, I get 60-0.333j, but it is not the correct answer.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Dec 18, 2009 #2


    User Avatar

    Staff: Mentor

    Challenging question! I'd approach it by writing the 3 KCL equations for the 3 nodes. Put an AC voltage source at the left feeding terminals ab, label the upper left of the xfmr "1", the bottom of the xfmr "2", and the upper right of the xfmr "3". Write those 3 KCL equations, and see if you can solve for the voltages and currents in the circuit. Once you have those, you should be able to solve for Zin = ______
  4. Dec 18, 2009 #3
    Thank You!, I would never thought of that...
  5. Dec 18, 2009 #4

    The Electrician

    User Avatar
    Gold Member

    Have you made any progress?

    If you already have the correct answer, what is it?
  6. Dec 19, 2009 #5
    I haven't tried solving yet, but the correct answer according to my instructor should be 210 - j2700 ohms. And thank you everyone for helping me out.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook