One usually derives Ampere's law by taking the curl of the magnetic field given by the law of Biot and Savartfor a volume distribution of currentsJ. In the derivation, one drops a term that contains∇ · J, in order to treat stationary processes. It is shown that if that term is kept one gets, for∇ × H, a term which is the usual conduction currentJplus a second term similar to Maxwell's displacement current, present even outside the current distributionJ. That extra term isδD0/δt, where D0 = ε0E0 and E0is the instantaneous Coulomb field produced by the charges in question.

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