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Currents and charge between spheres

  1. May 15, 2009 #1
    1. The problem statement, all variables and given/known data

    Consider two small conductive spheres in radius a and b located far from each other.
    In t=0 "a" sphere charged with Q and "b" sphere neutral. We connect the spheres by wire with resistance R.
    Find the charge on each sphere as a function of time.

    2. Relevant equations

    d[tex]\rho[/tex]/dt+divJ=0

    I=dQ/dt

    J=[tex]\sigma[/tex]E

    R=[tex]\rho[/tex]*(L/A)

    3. The attempt at a solution
    I'm assumed that the change in charge in one sphere is the same in the other sphere with opposite sign. I tried to understand what is the relevant electric field and where should I calculate it (outside the sphere? Inside the wire?). I think that capacitance
    Required here but the two spheres connected so it more like capacitor discharge… I'm lost.
     
  2. jcsd
  3. May 15, 2009 #2
    It is the same thing as connecting two capacitors to each other. So treat sphere 1 with capacitance C1, and the other with capacitance C2. And the charges will move from 1 to 2 until both capacitors have equal charge.
     
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