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Electro-mechanical oscillator confuses me

  1. Oct 29, 2005 #1
    Hello, everybody!
    I got a homework that confuses me totally. Any help is highly appreciated:

    Here's the scenario :

    Which frequencies are possible on the assumption that we have a harmonic oscillation?
    The changing of the charge on the upper plate by q and the momentary elongation x should be considered.

    I think 'harmonic oscillation' means that we have
    and its derivations as a solution for a differential equation but I can't find an accurate

    the springs are made of isulating material.
    I forgot to mention that we have a DC voltage, so the resistance of the capacitor is infinite. In contrast to a AC voltage it has no impendance. As a consequence of that we have a mechanical oscillation - not an electric one.
    It must look like this:
    m*s'' + k*s = E*q

    The electric field strengh E and the carge q must be replced by given parameters whereas the charge on the upper plate is influenced by the coil - especially because of self-induction that hampers the charging on the plate.
    That's all I can say. My problem is the right equation for the oscillation.
  2. jcsd
  3. Oct 29, 2005 #2


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    Homework Helper

    well, the natural frequency of oscillation doesn't depend on the driver.

    But even after the capacitor is fully charged, to the DC Voltage,
    the Energy stored in the inductor's B-feld will continue I flow.
    After Voltage overshoots V_DC , oscillation w~ sqrt(LC) damps to V_DC.

    Presume small oscillations, and small separation, so Q_bottom = - Q_top.
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