1. Limited time only! Sign up for a free 30min personal 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!

Phasor Domain Circuit

  1. Mar 6, 2014 #1
    1. The problem statement, all variables and given/known data

    NilssonEC9c.ch09.p055.jpg

    Where Vs = 120 ∠0° V

    2. Relevant equations

    All values are represented in ohms, so they are treated as resistors.

    3. The attempt at a solution

    Series inductor + resistor

    30+j10 ohms = 31.62∠18.435°

    Parallel resistor and inductor+resistor

    (1/50)= 0.02∠0°, 1/(31.62∠18.435°)= 0.0316∠-18.435°
    0.02∠0° + 0.0316∠-18.435° = .050968∠-11.31°
    1/(050968∠-11.31°) = 19.62∠11.31°

    Series [j10+parallel section]

    j10 + 19.62∠11.31° = 23.704∠35.746°

    Now the current

    120∠0° / 23.704∠35.746° = 5.062∠-35.746°


    Not sure how to set up the Voltage Division equation. I think I'm doing all the impedance calculations correctly though.
     
    Last edited: Mar 6, 2014
  2. jcsd
  3. Mar 6, 2014 #2

    donpacino

    User Avatar
    Gold Member

    assign symbols to the passive elements, then solve using the symbols. It makes the work easier to follow and easier to correct a mistake.

    L1=j10
    L2=J10
    R1-50 ohm
    R2=30 ohm

    series inductor + resistor
    R2+L2

    parallel resistor and inductor+resistor

    z1=1/(1/R1 + 1/(R2+L2))

    current= vs / (L1 + Z1 )
    now plug in #s
    Its much easier

    now lets get to solving the problem...
    Why do you need the current at this point in time?

    To set up the voltage division equation you use the same method that you would for all resistors
    Vo=Vin*R1/(R1+R2)

    so in this case Vn= Vin* Z1 / (L1+Z1)
     
  4. Mar 6, 2014 #3
    I thought I needed the current to eventually use V=IZ, but I guess not.

    I followed you up until you got to current. Why is Vs only over L1+Z1? Because you are calculating voltage drops over that outermost loop?

    Where did Vn come from as well?
     
    Last edited: Mar 6, 2014
  5. Mar 6, 2014 #4
    So for multiplication of phasors I use a cross product? What do I do for division?
     
    Last edited: Mar 6, 2014
  6. Mar 6, 2014 #5
    I have no idea how to solve what I think is the proper voltage division setup:

    (120∠0) [(10∠90) / (23.7∠35.75)]
     
  7. Mar 7, 2014 #6

    donpacino

    User Avatar
    Gold Member

    vn is the node between the 2 inductors.
    z1 is the parallel combo of the resistor and inductor+resistor. that plus the first inducotor is the total impedance of the circuit.

    for division you divide the amplitude and subtract the phase

    that is incorrect voltage division.

    Vn= Vin* Z1 / (L1+Z1), with vn being that middle node, and z1 being the parallel combo of the resistor and inductor+resistor
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Phasor Domain Circuit
  1. Phasor circuit (Replies: 1)

  2. Phasor circuit (Replies: 4)

Loading...