4. Three point charges -q, +q, and +q are on the x-axis as shown. The negative charge is at position (x, y, z) = (-a, 0, 0). One of the positive charges is at the origin and the other positive charge is at (+a, 0,0). a (a) What is the dipole moment of this system? Give both magnitude and direction. (b) Write down an expression for the voltage using monopole and dipole terms.

4. Three point charges -q, +q, and +q are on the x-axis as shown. The negative charge is at position (x, y, z) = (-a, 0, 0). One of the positive charges is at the origin and the other positive charge is at (+a, 0,0). a (a) What is the dipole moment of this system? Give both magnitude and direction. (b) Write down an expression for the voltage using monopole and dipole terms.