The exact relation between the displacement current and the conduction current: Comment on 'Time-dependent generalizations of the Biot-Savart and Coulomb laws,' by D. J. Griffiths and M. A. Heald [Am. J. Phys. 59, (2), 111-117 (1991)]

摘要

I introduce the exact relation between the displacement current epsilon(0)partial derivative E/partial derivative t and the ordinary current J. I show that epsilon(0)partial derivative E/partial derivative t contains a local term determined by the present values of J plus a nonlocal term determined by the retarded values of J. The nonlocal term implements quantitatively the suggestion made by Griffiths and Heald that the displacement current at a point is a surrogate for ordinary currents at other locations. (C) 2008 American Association of Physics Teachers.