Motivating the Biot-Savart Law

Introducing students to a new law is pedagogically challenging. One can just declare it as fact, but it is easier on (at least some) students if we can derive it when possible, or, if not, at least motivate it somehow. The Biot-Savart law is particularly challenging in this respect, because it is only derivable from more advanced formulations (such as Maxwell’s equations), which are in their turn merely stipulated (this is the approach of Feynman et al., for example). The other possibility is simply to declare its empirical truth, without details (see, for example, Griffiths).