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Homework Help: Find the electric field a distance z from the centre of spherical

  1. Nov 30, 2011 #1
    1. The problem statement, all variables and given/known data

    Find the electric field a distance z from the centre of spherical sphere of radius R which carries uniform density B. treat Z<R (inside) and Z>R (outside)………. By using law of cosine how to solve this problem?

    2. Relevant equations

    1/4∏εo∫ (σ da/ r^2) cos(theta)
    3. The attempt at a solution
    substituting r by law of cosin.. r=√R^2+z^2-2Rzcos(theta)
    1/4∏εo ∫[σ da/ R^2+z^2-2Rzcos(theta)]cos(theta)
    i am stuck here what should i do next
     

    Attached Files:

  2. jcsd
  3. Nov 30, 2011 #2
    Re: electrodynamics

    Hi...
    Is the charge density given by a surface density, or a volume density? When talking about a sphere and not a spherical shell, one ought to remember that the inside is filled(in this case with charge).
    In any case,
    Try the following:
    [itex]
    dA = rdr\sin(\theta)d\theta d\phi
    [/itex]
    [itex]
    dV = r^2dr\sin(\theta)d\theta d\phi
    [/itex]
    Phi goes from 0 to 2pi,
    Theta goes from 0 to Pi.
    r from zero to R.
    Try it,
    Daniel
     
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