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Homework Help: Parallel or Serial

  1. Feb 21, 2004 #1
    First take a look at the attachment (See reply below). We have to take the oscilloscope's impedance and the coaxial cable's impedance into account. And then we have to calculate the cutoff frequency of this.
    Given: Oscilloscope: R=1M Ohm // C=25pF
    Coaxial Cable: R=75 Ohm and C=68pF/m with L=0.85m

    My problem is that I don't know how to draw this. R and C from the Coaxial cable, are they serial or parallel? And the coaxial cable's impedance is that serial or parallel to the oscilloscope's impedance?

    If I know that, I can calculate the cutoff frequency and the voltages with different frequencies, but now I'm stuck. Thanks in advance.
    Last edited: Feb 21, 2004
  2. jcsd
  3. Feb 21, 2004 #2

    And here's the attachment :).

    Attached Files:

  4. Feb 22, 2004 #3
    Anyone? Or is my question not clear enough?
  5. Feb 22, 2004 #4
    Here's a hint: What is a capacitor? In asking this I'm prodding you into thinking about how a capicitor is physically made from there you should be able to figure out the problem. Also, do you know what a coaxial cable is and how it is constructed? If you don't know google it. If you do know, think about the construction of the coax cable and that of a capacitor. Good Luck
  6. Feb 22, 2004 #5
    Well a capacitor is actually two charged conductors very close to each other, so there's a voltage difference between them, right? And a coaxial Cable has an inner and an outer conductor, so those two conductors are responsible for the capacitance. That means the capacitance has to be parallel, right?

    SO it has to be one of this two schemes (attached)?
    Only I'm not sure wich one...

    Attached Files:

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