Potential between concentric spheres

[Kara386]

Homework Statement

A particle charge q and mass m moves in a circle radius r between two concentric spheres which are a distance d apart, where d<<r. There's a potential V between spheres. Find an expression for this potential.

Homework Equations

The Attempt at a Solution

Can I assume that these are like parallel plates so that $E = \frac{V}{d}$? The $F = qE$ and I can equate that to centripetal force. I'm just not sure if I can say that a sphere inside a spherical shell, which I assume is what the question means, would behave like that because of the curvature.

Thanks for any help!

 

[CWatters]

Can I assume that these are like parallel plates so that E=VdE=VdE = \frac{V}{d}? The F=qEF=qEF = qE and I can equate that to centripetal force.

That's what I would do.