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Calculating inductance of an LR and RLC Circuit?

  1. Apr 14, 2015 #1
    1. The problem statement, all variables and given/known data
    For both the LR and RLC circuit, a function generator is used to create a 1000 Hz square wwave of maximum amplitude.
    1) For the following LR circuit, the resistance is set to a 100 Ohms. Determine the inductance, L. How does the inductance vary if the resistance were increased to 200 Ohms

    5WUQFAq.png
    2) For the following RLC circuit, the capacitance is set to a 0.001 micro F. Determine the inductance, L.
    SBr0Irn.png


    2. Relevant equations
    2) F_0 = 1/ (2*pi* sqrt(LC))
    ω^2 = (1/LC)(1 - (C*R^2)/(4L))
    ω=2*pi*f


    3. The attempt at a solution

    1) I can't find any formulas for this one.
    2) For question 2, I don't know which equation should be used. Also, I assume that f=1000Hz. For the second equation, R is the total circuit resistance, C is the capacitance, and L is the inductance.
     
    Last edited: Apr 15, 2015
  2. jcsd
  3. Apr 15, 2015 #2
    I've found an equation for question 1.

    V=V_0(e^(-Rt/L))
     
  4. Apr 15, 2015 #3
    For question 1, I got the inductance to be 0.114 mH.
     
  5. Apr 18, 2015 #4
    bump
     
  6. Apr 19, 2015 #5

    rude man

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    You did? Without knowing anything about the signal at "Ch. 1"? Wow! Show us how!
     
  7. Apr 19, 2015 #6

    SammyS

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    Please give the problem statement as it was given to you. It clear that some critical information is missing.

    What does it mean for the function generator to produce a wave of maximum amplitude?

    Is it perhaps the wave at Ch. 1 which has to have maximum amplitude?
     
  8. Apr 19, 2015 #7
    Yes, my apologies. I've neglected to include the relevant oscilloscope readout.
    zYefk3g.jpg
    Vertical Scale: 100mV/DIV
    Horizontal Scale: 50 microsecond/DIV

    gfg8210-600.jpg
    Here is a the function generator used. Notice the AMPL knob to the right. Maximum amplitude means turning it all the way counterclockwise.
     
  9. Apr 19, 2015 #8
    Simple. Since I didn't know anything about what was in Ch. 1, I simply had to find it out. You can as well if you were to make the circuit as shown in the initial post.
     
  10. Apr 19, 2015 #9

    rude man

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    Yeh, but you didn't know L either. You were supposed to find L given Ch. 1.
    I see you did post the Ch 1 waveform later. Much better.
    It would further be helpful if you provided us with the amplitude of the square-wave generator, although one can estimate L based on the decay profile in Ch. 1.
     
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