A disk of radius R has a uniform surface charge σ on one side. A circular hole of radius R/2 is now cut in the center of the disk.
(a) Using the superposition principle and the result 2keπσ[(√R2+x2)-x], find the electric potential V along the axis of the disk at a distance x from its center (V=0 at x=∞).
(b) What is the electric potential at the center of the hole?
(c) What is the electric field at the center of the hole?