II. On the changes produced by magnetisation in the length of iron wires under tension

Abstract

In a paper communicated to the Royal Society about a year ago, I discussed the results of certain experiments made by Joule in relation to “the Effects of Magnetism upon the dimensions of Iron and Steel Bars.” It is well known that the length of an iron rod is in general slightly increased by magnetisation. Joule enunciated the law that the elongation is proportional in a given bar to the square of the magnetic intensity, and that it ceases to increase after the iron is fully saturated.