In Figure a, a particle of elementary charge +e is initially at coordinate z = 20 nm on the dipole axis (here a z axis) through an electric dipole, on the positive side of the dipole. (The origin of z is at the center of the dipole.) The particle is then moved along a circular path around the dipole center until it is at coordinate z = –20 nm, on the negative side of the dipole axis. Figure b gives the work W_a done by the force moving the particle versus the angle θ that locates the particle relative to the positive direction of the z axis. The scale of the vertical axis is set by W_as = 4.0 × 10^–30 J. What is the magnitude of the dipole moment?

(r 06-01) al