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Homework Help: RLC Circuit (lab session doubt)

  1. Mar 25, 2015 #1
    1. The problem statement, all variables and given/known data
    I have to answer a few questions about a lab session I did (university) and I'm really stuck with this one.
    The objective of the lab session was to find the self inductance (L) of a solenoid.

    In order to do that, I had a function generator exciting a solenoid with a high self-inductance coefficient. (see image)
    This one, at the same time, by magnetic coupling with the solenoid whose L we want to obtain, excites the RLC circuit, causing a transient response in the form of oscillatory damped tensions. We measured the period of those oscillations and with this formula

    we can easily get the self-inductance L. No problem with that... Now, the question I'm having trouble with is the following
    "Why do we use the high self-inductance solenoid instead of just connecting the function generator directly with the problem solenoid? Hint: Keep in mind that the internal resistance of the generator is 50 ohm "

    I don't know why!! :(
    2. Relevant equations


    3. The attempt at a solution
    Perhaps it has something to do with limiting the current?

    Thanks in advance!!
  2. jcsd
  3. Mar 25, 2015 #2
    Do you know how to refer impedances from one side of a transformer to the other?

    The internal impedance of the function generator and the impedance it sees from its terminals forms a voltage divider. If the two coils are tightly coupled and you have ##L \ll L_\mathrm{exc}##, then your system has a nice property in terms of the voltage that appears across the oscilloscope terminals.
  4. Mar 26, 2015 #3
    I think you forgot a factor of 2π.
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