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Homework Help: Two Spheres connected by a wire.

  1. Oct 12, 2009 #1
    Charge is placed on two conducting spheres that are very far apart and connected by a long thin wire. The radius of the smaller sphere is 5 cm and that of the larger sphere is 12 cm. The electric field at the surface of the larger sphere is 830 kV/m. Find the surface charge density on each sphere

    For the 12cm sphere I used this:


    Solved for Q

    Then divided by [tex]4\pi r^{2}[/tex], and got [tex]7.347 \frac{\mu C}{m^{2}}[/tex]

    I need a little help figuring out the charge density for the 5cm radius sphere.
  2. jcsd
  3. Oct 12, 2009 #2


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    Homework Helper

    When the two spheres are joined by a wire, their potentials are same.
    So kQ1/R1 = kQ2/R2
    Or (kQ1/R1^2)*R1 = kQ2/R2.
    But E = (kQ1/R1^2) is given.
    Find Q1 and Q2.
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