Lectures on electricity / by James Ferguson, F.R.S.

  • James Ferguson
Date:
1825
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on electricity / by James Ferguson, F.R.S. Source: Wellcome Collection.

    100/112 (page 94)
    EXPERIMENT IV. The arrangements in this experiment are to be the same as in the last: in order, however, to avoid the danger of fracturing the jar, adapt a paper rim to the inside, in such a manner as to reach about an inch above the internal coating Eight inches of wire being placed in the circuit, the slider is fo be set at thirty grains, and the turning of the machine resumed. When the charge is sufficiently intense, the beam of the electrometer will descend, and the charge will melt the eight inches of wire with the same appearances as the two inches in the last experiment. EXPERIMENT V. Arrange eight inches of wire in the circuit as in the last experiment; but instead of one jar charged to thirty grains, now employ two charges to fifteen grains. The wire will be melted in exactly the same manner as before: it therefore appears that the effect is equally increased by doubling the extent of coated surface, or the intensity of the charge. From many experiments of this kind, it has been concluded by Mr. Brook and Mr. Cuthbertson, that the action of electricity on wires increases as the square of increased power ; since two jars charged to any decree will melt four times the length of wire melted by one jar charged to the same degree. This law is not applicable when any considerable dif- ference exists between the thicknesses of the jars em- ployed : as thick jars display the same intensity with a comparatively small quantity of electricity, and conse- quently have less power in melting wires. Mr. Singer mentions the circumstance of a very large jar in his possession, which, from the extent of its coated surface, should have melted three feet of wire, with a charge of