Two point charges lie on the -axis: a charge at and a charge at
PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Electrostatic fields and potential · Electrostatic fields and potential
The Boundary-Value Problem, Ch The multipole expansion of the potential
Problem
Two point charges lie on the z-axis: a charge +2q at z=+d and a charge −q at z=−d, with q=1.0nC and d=4.0cm. Take the origin at the midpoint between them.
((a)) Find the total charge Q of the distribution.
((b)) Find the dipole moment p about the origin, as a vector along z^.
((c)) State which term of the multipole expansion, monopole or dipole, dominates the potential at large r, and explain why using how each term falls with r.