Question 1) A positive charge +q is located at the point x=0, y=-a and a negative charge -q is located at the point x=0, y=+a.
Derive an expression for the potential V at points on the y-axis as a function of the coordinate y. Take V to be zero at an infinite distance from the charges.
Question 2) A disk with radius R has uniform surface charge density σ.
A- By regarding the disk as a series of thin connection rigs, calculate the electric field V at a point on the disk's axis distance x from the center of the disk. Assume that the potential is zero at infinity.
B- Calculate -∂V/∂x.