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Homework Help: Black box Conumdrum: CL or LC order in a RLC circuit

  1. Jul 13, 2012 #1
    Hey everyone.

    Since it is nearest the end of the summer semester for the Lab component of my classes, Our professor is having do the 'Black Box' project. From the information he gave us, there are three component in a L-configuration, an inductor, capacitor, and a resistor. The Box itself had three connection (Red, Black and Green). For this week, he wanted us to determine the order of the components.

    My lab partner and I were able to determine that across two connections (Red and Black) that only purely resistive component exist (122.xxΩ , 0 Farads). Checking values across the Black and Green as well as Red and Green reveal a capacitor via an infinite resistance and a capacitor value of 33.35n Farads. Observing the waveforms across the red and black, only amplitude was affected, while either Black and Green or Red and Green revealed waveform transformation (square input resulted in a sine output with underdamping when approaching the peak square value). At around 102.8 Khz the output peaked. By using that knowledge that it had to be a bandpass, I determined that the inductor value had to be around 71.87uH.

    The problem me and my lab partner are running into; how can we tell the order of the impeding components if their interactions are symmetrical from the observations outside the black box?

    Attached Files:

  2. jcsd
  3. Jul 13, 2012 #2


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    Science Advisor

    No, you can't.

    It doesn't matter which way around you place the L and C in a series circuit.

    Your calculation seems OK.
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