Concerns about the effects of magnetic fields on human health require careful monitoring of our exposure to them. Mandatory exposure limits have been defined for electric and hybrid vehicle architectures, in domestic and work environments, or simply to shelter sensitive devices from unintended sources of magnetic disturbance. In a new study published in EPJ Plus, physicists Jose Manuel Ferreira and Joaquim Anacleto from the Trás-os-Montes e Alto Douro University in Portugal develop a method for deriving an approximate value of the circulation around a loop of the magnetic field generated by the flow of electric current in an arbitrarily-shaped wire of a given length.