Solution

ID: past-exam-of-the-quantum-condensed-matter-course-of-the-university-of-cambridge/2006/section-a/a3/c/i/solution

Constancy of each ionic electrochemical potential gives the Boltzmann distribution in the local electric potential:
Positive potential repels positive ions and attracts negative counterions. The coordinate measures distance from a locally planar surface; the same local relations hold for a spherical potential with its appropriate radial coordinate.

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