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Homework Help: 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

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

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

    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.

  4. Apr 15, 2015 #3
    For question 1, I got the inductance to be 0.114 mH.
  5. Apr 18, 2015 #4
  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


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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.
    Vertical Scale: 100mV/DIV
    Horizontal Scale: 50 microsecond/DIV

    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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