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Homework Help: Spherical capacitor and electric fields

  1. Apr 29, 2012 #1
    A spherical capacitor contains:
    Region1: solid spherical conductor (radius=0.5mm, Q=7.4 micro coulombs)
    Region2: surrounded by a dielectric material (er=1.8, radius extends to 1.2mm,
    Region3: outer spherical non-conducting shell (variable charge per unit volume p = 5r, outer radius=2.0 mm)
    Determine the electric field everywhere?
    2. Relevant equations



    Region 1: [1 r>r1] E = 0
    Region 2: [r1 < r < r2] E = 7.4*10^-6 / (4 *∏ *1.8 * ε *r^2) = 3.71*10^4/r^2
    Region 3: [r2 < r < r3] Q(r) = 5 ∏ (r4 − r40) = 2.19*10^-10 .
    E = ( 7.4*10^-6 + 2.19*10^-10) / (4 ∏ εo) = 6.64*10^4
    Total Electric Field = 3.71*10^4/r^2 + 6.64*10^4/r^2
    Does this look right
     
  2. jcsd
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