Electrical potential of charged sphere

[kasse]

Homework Statement

Two charged metal spheres are connected by a wire. Sphere A is larger than sphere B. The magnitude of the electrical potential of A...

a) is greater than at the surface of sphere B
b) is less than at the surface of sphere B
c) is the same as that at the surface of sphere B

The Attempt at a Solution

Electric potential: V = q/(4*pi*e₀*r)

Since the spheres are connected by a wire, their charge will be equal. We regard the charges at the spheres as point charges in the centers of the spheres. Then the magnitude of the electrical potential of A is less than at the surface of B since r_A > r_B

Why am I wrong?

 

[Dick]

I don't know how to say this without giving the whole thing away, but do you really think that if I connect a huge sphere with a lot of charge (like the earth) to a small sphere (like a steel marble) that they will they will split the charge equally? Something will be equal between the two spheres, but it won't be charge.

 

[kasse]

So c) is the correct answer. How can this be explained?

 

[michalll]

The potential on the surface must be constant, otherwise there would exist tangential field E that moves the charges until equipotential is reached.