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Homework Help: Application of Gauss's Law to Charged Insulators

  1. Oct 11, 2011 #1
    1. The problem statement, all variables and given/known data

    A cylindrical shell of radius 7.00 cm and length 240 cm has its charge uniformly distributed on its curved surface. The magnitude of the electric field at a point 19.0 cm ra- dially outward from its axis (measured from the midpoint of the shell) is 36.0 kN/C. Use approximate relationships to find (a) the net charge on the shell and (b) the electric field at a point 4.00 cm from the axis, measured radially outward from the midpoint of the shell.

    2. Relevant equations
    3. The attempt at a solution

    Could someone please explain to me why this does not work:

    Flux = Q/e = E*2pi*r*l

    Where I am thinking of Q in terms of an average AREA charge density * the area, and not a line density * a length.
    -- Is it because it lacks enough independent equations?
  2. jcsd
  3. Oct 11, 2011 #2

    Doc Al

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    Staff: Mentor

    Why do you think that doesn't work?
  4. Oct 11, 2011 #3
    Because I am currently getting a different answer than that given by the book - which is:

    +913 nC
  5. Oct 11, 2011 #4
    Okay it works... I've been using an incorrect value for e when solving from k - apologies.
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