Capacitance and Max field strength between two spheres?

Discussion in 'Homework Help' started by smarch, Jun 30, 2010.

  1. smarch

    Thread Starter Active Member

    Mar 14, 2009
    52
    0
    Can someone please help me with this question?

    A capacitor is formed by two concentric spheres whose radii are 25 cm and
    12.5 cm respectively, with a liquid insulant between them with relative
    permittivity 3. The potential difference between the spheres is 10 kV. Find (i)
    the capacitance and (ii) the maximum field strength in the gap between the
    two spheres

    Do I use this formua : V = -∫Edr+constant

    so, 10000 = q/2pi*eo*er * (1/25 - 1/12.5)

    Is this correct?
     
  2. smarch

    Thread Starter Active Member

    Mar 14, 2009
    52
    0
    ok, I worked out the capacitance:

    ∆ V = Q / (4πε0) ∫ (1/r^2) dr between the limis a to b

    = Q / (4πε0) { 1/a - 1/b)

    C = Q/∆ V = 4πε0) / (1/a - 1/b)

    But with the max field strength do i use : q = cv

    Then apply q to : E = q/4∏*εr*ε0*r^2

    Is that correct?
     
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