# Electric Potential of Two Spheres

1. Sep 4, 2006

### boderam

Problem:

An insulated spherical conductor of radius r1 carries a charge Q. A second conducting sphere of radius r2 and initially uncharged is then connected to the first by a long conducting wire. After the connection, what can you say about the electric potential of each sphere? How much charge is transferred to the second sphere? Assume the connected spheres are far apart compared to their radii. (Why make this assumption?)

I think I am confused about potential in general, so bare with me here. I know that for a point charge Q the potential at a point P is kQ/r. In class my teacher derived the potential for a sphere, in the case of the first sphere it would be kQ/r. The charge then distributes to the other sphere, but I am not sure how to derive the balance. I also know that the potential will be the same on both spheres since they are conducting, the electric field is 0. Let the first sphere have charge Q1 and the second Q2, then Q = Q1 + Q2. V = kQ1/r = kQ2/r since the potentials are equal...I don't think is right though. Someone want to clear this up for me? Thanks. A lot.

2. Sep 4, 2006

### boderam

anyone know how to do this?

3. Sep 5, 2006

### Tomsk

Yeah that's right, the potential of each sphere is equal after they're connected, so kQ1/r1=kQ2/r2.