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Circuit Analysis

  1. Mar 5, 2007 #1
    1. The problem statement, all variables and given/known data

    The question given to me will be written in red and then I will show my working out.

    Any feedback appreciated.

    (Theres more to it than what I will write here, but I will attempt to leave it as brief as possible here.

    [​IMG] (This is supposed to be an unknown circuit.

    Tests are applied at terminals AB of each passive linear circuits 1, 2, 3 and 4 Here I am just going to worry about 1 and 2.

    The test are:

    a) Apply 6v d.c and measure the current (Id.c) taken by the circuit.
    b) Apply 10v r.m.s a.c at 1kHz and measure the current (Ia.c) taken by the circuit and its phase angle relative to the applied voltage.
    c) Apply 10v r.m.s a.c at 2kHz and measure the current (Ia.c) taken by the circuit and its phase angle relative to the applied voltage.

    Test Results:

    Circuit 1
    when 6V: 57.3mA (Id.c)
    when 10v r.m.s at 1kHz: 82mA 31° Lag
    when 10v r.m.s at 2kHz: 61mA 50° Lag

    Circuit 2
    when 6V: 0mA (Id.c)
    when 10v r.m.s at 1kHz: 5mA 53° Lead
    when 10v r.m.s at 2kHz: 7mA 33.5° Lead

    From the test results determine the minimum component equivalent circuit for each of the actual circuits.

    For each circuit:
    1. Determine the d.c resistance of the circuit.
    2. Determine the complex impedance and complex admittance of the circuit for each frequency.
    3. From these results logically determine the configuration of the equivalent circuit.
    4. Determine the component values.
    5. Draw the circuit showing component values.

    2. The attempt at a solution


    1. d.c resistance of the circuit.


    2. Complex Impedance and Complex admittance.

    Complex Impedance at 1kHz



    Complex Impedance at 2kHz


    Complex Admittance at 1kHz



    Complex Admittance at 2kHz


    3. Logical determination of the circuit configuration.

    Doubt: Is this just explaining what the circuit is made up of?

    Current flows when dc is supplied, this means that there is no capacitor connected as capacitors do not allow current flow when connected to d.c

    Current is always lagging voltage, this suggests that an inductor is present in the circuit.

    This is a Resistor and Inductor circuit in series

    4. Component Values.



    This looks like d.c resistance (number one above).




    We know that...


    I have also done circuit two, but I will not be posting about it until I am 100% sure about this first one.

    I know this has been a bit long, :blushing: but thank you very much.
    Last edited: Mar 5, 2007
  2. jcsd
  3. Mar 6, 2007 #2


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    In a parallel RC circuit d.c. current flows.
  4. Mar 6, 2007 #3
    Thought of that as its a bit obvious, because current would just flow through another path, I'll better leave that out then. :wink:

    In this case we have an RL circuit don't we?
    Last edited: Mar 6, 2007
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