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Phasors and Imaginary and Real help

  1. Feb 3, 2009 #1
    Ok so i just want to clear up something about phasors and just circuit input functions in general. So based on the imaginary and real graph, where imaginary is like the y axis and the real is the x axis, when lets say a circuit falls on the imaginary axis is it considered a stable circuit? Do these exist in real life ? If it falls on the right side of the imaginary axis i know this means there very unstable , and that they rarely exist and the circuits operates to bring them back to the left side of the imaginary axis to make them stable again.

    Please tell me if me if my thinking is right, and that part about the imaginary axis, if there is solution right on it

  2. jcsd
  3. Feb 4, 2009 #2
    Could you clarify your questions? Are you talking about a voltage function or current function? The only thing that I know about an input function's phasors deviating from the real axis (∠0°,∠180°,∠-180° ) or imaginary axis (∠90°,∠270°,∠-90°) is due to the characteristics of the circuit's impedance. Is it purely resistive, does it have inductive reactance, or capacitive reactance?
  4. Feb 4, 2009 #3
  5. Feb 4, 2009 #4
    th3...your question appears inconsistent..first you say input functions then you reference a circuit.
    usually you characterize a circuit via an input function, a transform representing the circuit characteristics, and an output....you seem to have the first two mixed.

    There can be unstable circuits to be sure and these will be characterized by certain feedback characteristics. If the feedback reduces such instability by appropriately altering the input signal control is achieved..

    See http://en.wikipedia.org/wiki/Feedback#In_electronic_engineering

    and possibly Nyquist stability criterion :
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