. The medical and surgical uses of electricity. . e south. If the magnet be disturbedin any way, and forced temporarily out of position, it at once and uni-formly returns. Polarity is a quality that belongs not only to magnetism, but also toother forms of electricity, and to light and the other great forces. The poles of a magnet are always at its ends, for here the attractivepower is greatest. This can be demonstrated by a very simple experi-ment. If a magnetic bar be rolled in a pile of iron filings, it will befound that these adhere to the bar most firmly and in the greatest quan-tity at or
. The medical and surgical uses of electricity. . e south. If the magnet be disturbedin any way, and forced temporarily out of position, it at once and uni-formly returns. Polarity is a quality that belongs not only to magnetism, but also toother forms of electricity, and to light and the other great forces. The poles of a magnet are always at its ends, for here the attractivepower is greatest. This can be demonstrated by a very simple experi-ment. If a magnetic bar be rolled in a pile of iron filings, it will befound that these adhere to the bar most firmly and in the greatest quan-tity at or near its poles. The quantity that adheres is less as we approachthe middle of the bar. Neutral Line.—\xi long bars there is always a place at the middle, ornear to it, where no filings are attracted. This space is variously termedthe neutral or magnetic zone, or magnetic equator, or point of indiffer-ence. Another familiar experiment is to pass an iron ball, suspended by astring or thread, near to a magnet from end to end. It is observed that. the ball is attracted very little, or not at all, in the middle, but that theattractive power is increased as we bring it toward either end. If anysubstance be placed between the ball and the magnet, the attraction is justas marked, unless the interposed substance itself contains iron. Nearlyall substances that are not themselves magnetic are capable of transmit-ting the magnetic influence. Another feature of magnetic polarity is that like poles repel, and un-like poles attract, each other. If one magnetic bar be suspended freely inthe air, and another be brought near to it, it will be found that the northpole of one is attracted by the south pole of the other, and vice versa—inshort, that the like poles repel, while the unlike attract. Magnetism of Broken Magnets.—\i a bar that has been magnetized bebroken in the middle, each half will have two poles and a neutral point inthe centre. If one of these halves is broken in the middle,
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1896
