A disk with radius R has uniform surface charge density σ.

Part A

By regarding the disk as a series of thin concentric rings, calculate the electric potential V at a point on the disk's axis a distance x from the center of the disk. Assume that the potential is zero at infinity. (Hint: Use the result that potential at a point on the ring axis at a distance x from the center of the ring is V=14πϵ0Qx2+a2√ where Q is the charge of the ring.)

Express your answer in terms of the given quantities and appropriate constants.

Part B

Calculate −∂V/∂x.

Express your answer in terms of the given quantities and appropriate constants.