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How long will a lc tank circuit oscillate after power is removed?

  1. Aug 9, 2011 #1
    If a lc resonant tank circuit is disconnected from power how do you determine the length of time it will oscillate.

    L=1 henry, 500 ohms
    Fres=22,507 hz
  2. jcsd
  3. Aug 9, 2011 #2
    It will decay exponentially. Usually you specify the time it takes to reach a certain ratio of the maximum (usually 1/e or about 36%), since mathematically the amplitude of oscillations will never reach zero.
  4. Aug 9, 2011 #3
    Ok, so how would I calculate that?
  5. Aug 10, 2011 #4


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    The time constant is 2Q/frequency; where Q is the quality factor of the circuit.
    In order to calculate Q you need to know the losses in the circuit; if the above values are for an ideal circuit (meaning the 500 ohms are the only dissipate losses in the circuit) them you can calculate Q from them (google Q factor)
  6. Aug 10, 2011 #5
    Awesome, thank you.
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