Paper, 'Note on specific inductive capacity' by John Hopkinson

Description

Hopkinson writes: 'Consider a condenser formed of two parallel plates at distance x from each other, their area A being so great, or the distance x so small, that the whole of the lines of force may be considered to be uniformly distributed perpendicular to the plates. The space between the plates is occupied by air, or by any insulating fluid. Let e be the charge of the condenser and V the difference of potential between the plates. If the dielectric be air, there is every reason to believe that V ∞ e, that is, there is for air a constant of specific inductive capacity. My own experiments ([1880] ‘Phil. Trans,’ vol. 172, p. 355) show that in the case of flint-glass the ratio of V to e is sensibly constant over a range of values of V from 200 volts per cm. to 50,000 volts per cm. From experiments in which the dielectric is one or other of a number of fluids and values of V upwards of 30,000 volts per cm. are used, Professor Quincke concludes (‘Wiedemann, Annalen,’ vol. 28, 1886, p. 549) that the value of e/V is somewhat less for great electric forces than for small. From the experiments described in that paper, and from his previous experiments (‘Wiedemann, Annalen,’ vol. 19, 1883, p. 705, et seq.) he also concludes that the specific inductive capacity determined from the mechanical force resisting separation of the plates is 10 per cent. to 50 cent. greater than that determined by the actual charge of the condenser. The purpose of the present note is to examine the relations of these important conclusions, making as few assumptions as possible.'

Annotations in pencil and ink throughout. Includes a small diagram of a graph.

Subject: Thermodynamics

Received 9 November 1886. Read 16 December 1886.

A version of this paper was published in volume 41 of the Proceedings of the Royal Society as 'Note on specific inductive capacity'.

Reference number

PP/9/16

Earliest possible date

1886

Physical description

Ink and graphite pencil on paper

Page extent

15 pages

Format

Manuscript
Diagram