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I Cavity in a dielectric material

  1. Jun 30, 2017 #1
    Hello friends.

    If i have a dieletric material ( w/ a hole) and apply an uniform eletric field on it, the eletric field in the hole will stay null ?

    Peace.
     
  2. jcsd
  3. Jun 30, 2017 #2

    Paul Colby

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    No, why would one think so? The normal component of ##D=\epsilon(r)E## and the tangent component of ##E## are continuous across dielectric (actually all) material boundaries.
     
  4. Jun 30, 2017 #3
    But if i close a surface within the hole, there woud not be any charge inside, so ∫ D ⋅ dS = 0 and D = 0.
     
  5. Jun 30, 2017 #4

    Paul Colby

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    Not if as much ##D## flux exits as enters the volume as leaves which is actually the case. My suggestion is work a 1-D problem that's simple to solve completely. Try a 3 layer parallel plate capacitor with a void layer inside where you ignore fringing fields. Continuity of normal ##D## along with the total voltage drop yields an answer. You will find an ##E\ne0## in the air gap.
     
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