J. C. Maxwell’s, ‘Dynamical theory of the electromagnetic field’

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                                Electric Absorption 

(85) When the dielectric of which the condenser is formed is not 
a perfect insulator the phenomena of conduction are combined 
with those of electric displacement. The condenser, <s>after being<\s> when left 
charged gradually loses its charge and in some cases after being 
discharged completely it gradually acquires a new charge of the 
same sign as the original charge, and this finally disappears 

These phenomena have been described by Faraday (Series XI 
and by M,sup>r<\sup>r F Jenkin (Report to Board of Trade on Submarine Cables) 
and may be classed under the name of "Electric Absorption" 

(86) We shall tke the case of a condenser of any 
number of parallel layers of different materials. If a constant 
difference of potentials <s>is kept up<\s> between its extreme surfaces 
is kept up for a sufficient time till a condition of permanent 
steady flow of electricity is established, then each bounding surface 
will have a charge if electricity depending on the nature of 
the substance on each side of it. If the extreme surfaces 
be now discharged, these internal charges will gradually 
be dissipated and a certain charge may reappear on the extreme 
surfaces if they are insulated, or, if they are connected by a conductor 
a certain quantity of electricity may be urged through the conductor 
during the reestablishment of equilibrium 

Let the thickness of the several layers of the condenser be 
a<sub>1<\sub> a<sub>2<\sub> &c <s>and the whole thickness a<\s> 

Let the values of k for these layers be respectively k<sub>1<\sub> k<sub>2<\sub> k<sub>3<\sub> 
and let <s>a<sub>1<\sub>/k<sub>1<\sub> + a<sub>2<\sub>/k<sub>2<\sub> &c = a/k<\s> a<sub>1<\sub>k<sub>1<\sub> + a<sub>2<\sub>k<sub>2<\sub> &c = ak (50) 
where k is the "electric elasticity" of air and a is the thickness 
of an equivalent condenser of air 

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Manuscript details

James Clerk Maxwell
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Cite as

J. C. Maxwell’s, ‘Dynamical theory of the electromagnetic field’, 1864. From The Royal Society, PT/72/7



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