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Griffith's Figure 2.24

  1. Mar 9, 2008 #1
    [SOLVED] Griffith's Figure 2.24

    1. The problem statement, all variables and given/known data
    This question refers to Griffith's E and M book.

    In the paragraph above this figure, Griffith's says that the E-fields cancel in regions i and iii. He does NOT mean cancel completely, correct? That is, the field is NOT 0 in those two regions, correct?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 9, 2008 #2


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    Yes they cancel completely if you assume infinite plates. Of course in real life there are no infinite plates.
  4. Mar 9, 2008 #3
    Oh I see. It is because equation 2.17 tells us that the E-field is independent of the distance from the plates.
  5. Mar 9, 2008 #4


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    Exactly. This is the special property of an infinite surface charge distribution.

    A point charge has an E field that goes like 1/r^2. A uniform line of charge (infinite) has an E field going like 1/r. A uniform infinite surface charge distribution has a constant E field
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