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Rubber balloon in electric field

  1. Feb 11, 2009 #1
    1. The problem statement, all variables and given/known data
    A rubber balloon has a charge q evenly distributed over its surface. It is put into a uniform electric field of 120 N/C. What is the charge inside the balloon?

    2. Relevant equations

    3. The attempt at a solution
    I thought that E inside would be 120 since before it is put into the electric field, E inside is 0(true or not?). When it is put into the field you use the principle of superposition and they add to 120 N/C?

    Any insight to this would be helpful. I handed it in this morning but I'd still like to know if I made correct assumptions.
  2. jcsd
  3. Feb 11, 2009 #2
    Assuming the balloon to approximate a spherical shell then I'd say you're right about the E-field, but you are missing a step, which is using the polarizability to relate the field to the dipole moment created and ultimately the charge on the inside.
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