Finding unknown values in a circuit

Discussion in 'Homework Help' started by labhelp, Jan 28, 2010.

  1. labhelp

    Thread Starter New Member

    Jan 28, 2010
    28
    0
    In my lab we were given 3 black boxes and a sheet with 3 different circuits(shown in the attached pdf on page 3). We were then told to find out which box went with which circuit then find the values of all of the components. We found the transfer functions for each circuit then ran a voltage sweep on the actual circuit to see what the graph would do. We figured out which box went with which circuit and also figured out the values of the resistors. We are stuck on how to figure out the value of the capacitors. We have a lot of equipment available like a Oscilloscope, DMM, waveform generator, and a DC power supply.

    Can I get some advice on how i can obtain the capacitances for each of the circuits? thanks in advance.
     
    Last edited: Jan 28, 2010
  2. kdillinger

    Active Member

    Jul 26, 2009
    141
    3
    You forgot the PDF.
     
  3. labhelp

    Thread Starter New Member

    Jan 28, 2010
    28
    0
    thanks, pdf added
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You do know that capacitors' impedance changes with frequency?
     
  5. labhelp

    Thread Starter New Member

    Jan 28, 2010
    28
    0
    yeah i do i'm just having trouble grasping what I need to do to figure it out
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Pick two frequencies to apply to the box input. Calculate Xc for those frequencies, and use that to solve the network and get the magnitude of the output for both situations. The difference between the two will let you determine the size of the capacitor.
     
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