On the heating effects of electricity and magnetism / W.R. Grove.

  • William Robert Grove
Date:
[1852]
Catalogue details

Licence: Public Domain Mark

Credit: On the heating effects of electricity and magnetism / W.R. Grove. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    3/6 (page 121)
    In the cases of heating or ignition of a conjunctive wire or con- I ducting body through which what is called Electricity is transmitted, we have many evidences that the matter itself is affected, and in some cases temporarily, in others, permanently changed ; thus if a wire of ■ lead is ignited to fusion by the voltaic battery, the fused lead being kept in a channel to prevent its dispersion, it gradually shortens, ; and the molecules seem impressed with a force acting transversely to the line of direction of the electricity ; at length the lead gathers Iup in nodules which press on each other as do, to use a familiar illustration, a string of figs. ; With Magnetism we have many instances of the molecular change ! which a ferreous or magnetic substance undergoes when magnetized. Ilf the particles are free to move, as for instance iron filings, they arrange themselves symmetrically. An objection may be made arising from the peculiar form of the iron filings, but Mr. Grove in the year 1845, shewed that the supernatant liquid in which magnetic ■ oxide had been formed, and which contains magnetic particles not mechanically but chemically divided, exhibits when magnetized a change in the arrangement of the molecules, as may be seen by its effect on transmitted light; — a molecular change is also evidenced I by the note or sound produced by magnetism, and by other effects. Assuming that the molecules of iron change their position inter se upon magnetization, then by repeated magnetization in opposite directions, something analogous to friction might be produced ; and just as apiece of caoutchouc when elongated produces heat, (as it was on this occasion experimentally shewn to do) so a bar of soft iron might be expected when subjected to rapid changes in its magnetic state, to exhibit thermic effects. With the aid of the large magnet of the Institution and of a commutator for changing the direction of the Electricity a bar of soft iron was alternately magnetized in opposite directions ; and in a few minutes a thermometer placed in an aperture in the iron shewed a rise of temperature of 1,5° Fahrenheit; the bar being separated from the magnet by flannel, and the magnet being at a notably lower temperature than the bar, this heat could in nowise be attributed to conduction. The effect of Electricity in the disruptive discharge as in the Voltaic arc and the electric spark, would seem at first sight to offer greater difficulties of explanation on the dynamic theory. The brilliant phenomenal effects of the electric discharge, and the apparent absence of change in the matter affected by it, would at first lead the observer to believe that Electricity was a specific entity. With ordinary flame or the apparent effects of combustion however, the idea has to a great extent been abandoned that such visual effects are due to specific matter, and it is regarded by many as an intense motion of the particles of the burning body. So with Electricity, if in regard to the disruptive discharge it can be shewn that the matter of the terminals or of the intervening medium is -changed, the necessity for the assumption of a fluid or ether ceases, and, to say the least, a possibility of viewing Electricity as a motion or affection of ordinary matter is opened.