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Inserting metal to parallel plate capacitor

  1. Feb 15, 2015 #1
    If there is a parallel plate capacitor with plate area, A, plate separation, d, and a slab of copper of thickness, b, is inserted exactly halfway between the plates. How to find it's new capacitance, C', and new potential difference, V' ?

    Answer: V' = E(d-b) and C' = εA / (d-b)

    I understand that there would be no effect on the electric field and E = Vd, and there is no electric field inside the copper. Is this why we exclude the thickness of the copper when calculating V' ? And why also do the same for capacitance? Thank you
  2. jcsd
  3. Feb 15, 2015 #2


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    Staff: Mentor

    It is the same as having 2 capacitors in series, each having one of the narrow air gaps as its own, and the sides of the metal insert forming a plate for each of the new capacitors. Yes, there is no voltage gradient across the copper.
  4. Feb 15, 2015 #3
    thank you so much. I understand it.
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