Charges of are located at both and , and a charge of is located at on the y-axis. This arrangement of charge can be visualized as two opposing dipoles.
a) Find the electric field (magnitude and direction) at an arbitrary point on the x-axis.
b) What is nonzero term in the expansion of the electric field evaluated far from the charges, i.e. - for ? Your answer should be a series of terms in inverse powers of .