Are there any instances where electromagnetic force from a point source doesn't follow the inverse square law?
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$\begingroup$ there is no magnetic point source and a carge as electric point source follows always the inverse square law. so what do you think of as "the point source"! $\endgroup$– trulaCommented Nov 5, 2022 at 15:27
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$\begingroup$ Why do you think Coulomb’s Law might have exceptions? If it did, it wouldn’t be a law. $\endgroup$– GhosterCommented Nov 5, 2022 at 16:55
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2 Answers
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Yes, there is indeed, but not in a 3-dimensional space. If the space dimension is arbitrary, let's call it $d$, then the electromagnetic field of a point charge scales like
$$\left|\vec E\right|(r) \sim \frac{1}{r^{d-1}}$$
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An ideal point dipole, quadrupole, etc. follow inverse cube, quad, etc. laws.
These are physical idealizations since a point dipole involves putting two charges infinitesimally close together while letting the magnitude of each charge go to $\infty$ so as to keep the dipole moment constant. A discussion of ideal vs. physical dipoles is given in Griffiths's Introduction to Electromagnetism.
So, I think it depends on what you mean by point source.
answered Nov 7, 2022 at 18:33