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Will a resonator change its Freq while energy is added?

  1. Aug 6, 2014 #1
    Consider this, will resonator change its frequency while energy is being added or removed?
    Should not matter if the resonator is mechanical or electrical.
    Last edited: Aug 6, 2014
  2. jcsd
  3. Aug 6, 2014 #2


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    In real life, yes. In elementary physics textbooks, no.

    The real world is nonlinear. The examples in elementary textbooks usually are not, because nonlinear problems are too hard for beginners to solve.

    To make an obvious comment about a real word resonator - if you add enough energy, something will break (mechanical) or burn out (electrical).
  4. Aug 6, 2014 #3
    Thank you,

    So considering two tuning forks, same resonant frequency without load, coupled k~0.1 and freely swinging in synchronization.
    Now when one adds energy to the first tuning fork and dampen, not excessively, the second fork, they would move out of synchronization?
  5. Aug 7, 2014 #4


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    I think that, for energy to be added to a free oscillator, there must be a finite phase lead in the added signal (and vice versa). This would have the effect of producing a resultant that has a phase, different from the original oscillation. With two coupled oscillators, at any given time, one is ahead or behind the other in phase and the energy oscillates between the two at their difference frequency. So I would expect a phase modulation (AKA differentiated FM) of each oscillation at that difference frequency.
  6. Aug 7, 2014 #5


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    Depends how you add energy I suppose. A slightly damped oscillator will have a slightly lowered frequency, so if you think of your energy addition as (magically) the opposite of damping, maybe it should speed up the oscillator. :)
  7. Aug 8, 2014 #6


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    You say they have the same resonant frequency BUTTTTTTT, when you couple them together, you are effectively adding in another component between the two. Another mode of oscillation (a frequency difference) has been introduced. I have heard of highly stable (powered) oscillators being brought close to each other and then starting to act up by beating together, despite not being explicitly connected even. A very high Q implies minuscule power being needed to keep it going so (and a very low bandwidth). A second oscillator, with a frequency within that bandwidth, can affect it. When you say they are "in synchronisation", I think you should acknowledge that they are actually driving each other apart - if the coupling is symmetrical. If one is driving and the other is driven, the driven frequency will be pulled to that of the driver. (There is no such thing as perfect synchronisation for two independent oscillators - they will each have their own frequency.)
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