Three point charges are placed on the y-axis: a charge q at y=a, a charge -2q at the origin, and a charge q at y=-a.
A. Find the magnitude of the electric field at points on the positive x-axis. Express your answer in terms of the variables q, x, a and appropriate constants.
B.Find the direction of the electric field at points on the positive x-axis.
C.Use the binomial expansion to find an approximate expression for the magnitude of the electric field valid for x gg a. Express your answer in terms of the variables q, x, a and appropriate constants.