Three charges (+q,-2q, and+q) are arranged along the z-axis at z = d/2, z = 0, and zd/2, respectively.
a) Determine Vand E at a distant point P(R, 0, Φ).
b) Find the equations for equipotential surfaces and streamlines.
c) Sketch a family of equipotential lines and streamlines.
(Such an arrangement of three charges is called a linear electrostatic quadrupole.)