Maxwell on Displacement Current


Early Maxwell on Electric Displacement

by Ivor Catt, 12March 2007



Maxwell's book came later; Maxwell, James Clerk, "A Treatise on Electricity and Magnetism". Clarendon Press, Oxford. 1873.

Maxwell's early paper

THE LONDON, EDINBURGH AND DUBLIN PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE. [FOURTH SERIES] MARCH 1861. XXV. On Physical Lines of Force, By J. C. MAXWELL, Professor of Natural Philosophy in King's College, London.


"p14 [my computer says "40 of 62"]



As long as electromotive force acts on a conductor, it produces a current which, as it meets with resistance, occasions a continual transformation of electrical energy into heat, which is incapable of being restored again as electrical energy by any reversion olf the process.

Electromotive force acting on a dielectric produces a state of polarization of its parts similar in distribution to the polarity of the particles of iron under the influence of a magnet, and, like the magnetic polarization, capable of being described as a state in which every particle has its poles in opposite conditions.

In a dielectric under induction, we may conceive that the electricity in each molecule is so displaced that one side is rendered positively, and the other negatively electrical, but that the electricity remains entirely connected with the molecule to another.

The effect of this action on the whole dielectric mass is to produce a general displacement of the electricity in a certain direction. This displacement does not amount to a current, because when it has attained a certain value it remains constant, but it is the commencement of a current, and its variations constitute currents in the positive and negative direction, according as the displacement is increasing or diminishing. The amount of the displacement depends on the nature of the body, and on the electromotive force; so that if h is the displacement, R the electromotive force, a dn E a coefficient depending on the nature of the dielectric, R = -4(pi)E(squared)h

and if r is the avlue of the electric current due to displacement, r = dh/dt

These relations are independent of any theory about the internal mechanism of dielectrics [this is the smoking gun - Ivor Catt, 12 March 2007]; but when we find electromotive force producing electric displacement in a dielectric, and when we find the dielectric recovering from its state of electric displacement with an equal electromotive force, we cannot help regarding the phenomena as those of an elastic body, yielding to a pressure, and recovering its form when the pressure is removed.

.... "



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