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Mechanical equivalent of a coil

  1. Feb 21, 2008 #1
    Hi. This is a simple one (I think):

    We all know a swing, or simple mass on a spring, moves in harmonic motion, and has a specific resonative frequency. We also know that the RCL circuit (which includes a coil and a capacitor) reacts similarly to an external oscillator, also with a specific frequency which gives the highest output. Both systems are equivalents, right?
    So my question is: If we decide the mechanical velocity is equivalent to the current, and the spring equivalent to the capacitor, what is the mechanical equivalent of a coil?
  2. jcsd
  3. Feb 21, 2008 #2
    Your question makes some assumptions that might need refined. We might say, for example, that the spring compliance is analogous to capacitance, but I would not say that a spring is equivalent to a capacitor. But, that aside, do you see any relationship between the mass and inductance?
  4. Feb 21, 2008 #3
    Thanks for your amendment.
    Mass, ha? Yes, this is what I thought. This is all under the analogy that velocity transforms to current. Can you therefore somehow conclude that under a different analogy that inductance would be like the elasticity of the spring (I mean with regards to current being analogous to some other variable)? Or is the previous analogy the only valid one?
  5. Feb 21, 2008 #4
    Also, regarding the original analogy: taking a long conductive wire and folding it in circles, creating a coil, would increase inductance without lengthening the wire... am I right? Is there a way to increase "mechanical inductance" (meaning mass) without actually increasing mass itself?

    If my assumptions above are correct, I thought that putting the mass on a table and rolling it with static friction generating angular momentum would accomplish that. Are my thoughts correct?
  6. Feb 22, 2008 #5
    I believe you are correct about other analogies, but I am at least twenty years away from looking at this and feel out of my depth without reviewing. So, I'm gonna pass and ask you to Google "mechanical analog inductance" or "mechanical analog capacitance" and see what you find.
  7. Feb 24, 2008 #6
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