Multipole expansions of electric charge and current distributions and the fields those multipoles create are a fundamental pillar of electromagnetic theory, but explanations and examples are rare beyond a dipole. In this paper we describe a low-cost exploration of magnetic multipoles. Using the field from ideal magnetic dipoles and a simple binomial approximation, we show that each multipole obeys B ∝ r n , with n = −3, −4, −5, −6 for a dipole, quadrupole, sextupole, and octupole, respectively. Using commercially available NdFeB magnets and the magnetic field sensor inside a smartphone, we experimentally verify the power-law dependence of the multipole configurations. Finally, the open-source Python library Magpylib can simulate the magnetic field of arbitrary permanent magnet distributions, which also shows the same power law dependence for the different multipole configurations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.