Introduction to Electrodynamics · Problem 3.46

Potentials — David J. Griffiths

Physics · multipole-expansion

Problem

A thin insulating rod, running from z=−az = -a to z=+az = +a, carries the indicated line charges. In each case, find the leading term in the multipole expansion of the potential: (a) λ=kcos⁡(πz/2a)\lambda = k\cos(\pi z/2a), (b) λ=ksin⁡(πz/a)\lambda = k\sin(\pi z/a), (c) λ=kcos⁡(πz/a)\lambda = k\cos(\pi z/a), where kk is a constant.

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