II. On the heating effects of electric currents

Abstract

The production of heat in electrical conductors due to the trans­ference of electricity through them has become a matter of very great practical importance. A knowledge of the variation of the law, due to the dimensions and character of the conductor, is essential for lightning protectors and for the leads of electric lights. Atmospheric electricity has proved a great danger to insulated wires, subterranean and submarine, and to telegraphic apparatus generally. Not only do the direct discharges of atmospheric electri­city enter the wires, but very powerful currents are induced in neighbouring wires when ijhese discharges take place, either between cloud and cloud or between cloud and earth. Various plans have been devised to protect apparatus and wires from these currents. Lightning protectors based on the effect of points, on the facility of discharge through vacua, on the low resistance of thin air-spaces to high potential, and on the fusibility of thin wires, have been used.