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Find the relative permittivity

  1. Oct 8, 2014 #1
    Consider a commonly-used capacitor made from two circular
    parallel plates with a ceramic dielectric between them. The plates have 12.5 mm diameter and the whole thing is 3 mm thick with a capacitance of 10 nF. Neglecting the finite thickness and extent of the plates, what
    relative permittivity must the material between the plates have to provide this capacitance?
    Allowing for the finite thickness of the plates, and of the insulation wrapping the outside of
    the whole thing, is this an underestimate or overestimate of the permittivity?

    I'm really not sure how to start at all. Without filling in details, can someone please explain how I would go about this problem?
  2. jcsd
  3. Oct 13, 2014 #2
    Thanks for the post! Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. Oct 13, 2014 #3


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    Gold Member

    In SI units,
    C=(relativity permittivity)*A/d
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