Electric quadrupole. Figure 22-46 shows a generic electric quadrupole. It consists of two dipoles with dipole moments that are equal in magnitude but opposite in direction. Show that the value of E on the axis of the quadrupole for a point P a distance z from its center (assume z ? d) is given by in which Q (= 2qd²) is known as the quadrupole moment of the charge distribution.

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Principle(s)/ Key idea(s), Equations corresponding to key ideas, Analytic solution, Numeric solution, Final Answer, Unit check, Number check ******