It is shown how to regard Maxwell’s equations for both periodic, putting together emission and radiation fields, and non-periodic phenomena, discussing both the time dependent equations as well as the role played by the time-independent ones. The difference in approach resulting from the quasi-permanent approximation, in which the sources feed the fields, and that of the exact equations, in which, strictly speaking, that is no longer true, is commented.
Maxwell’s equation; quasi-permanent states; periodic phenomena; aperiodic phenomena