Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . STEEL MAGNETS CHARGED 189 venient for charging permanent magnets. A shortsteel bar, if applied like an armature to the polesof an electro-magnet of the U form, will becomestrongly magnetic, the end which was in contactwith the north pole acquiring south polarity. Alonger bar may be charged, by employing the sameprocess that has been described in 251, for touchingby steel magnets. 303. Bars of the U form are most readily mag-netized by drawing them fro
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . STEEL MAGNETS CHARGED 189 venient for charging permanent magnets. A shortsteel bar, if applied like an armature to the polesof an electro-magnet of the U form, will becomestrongly magnetic, the end which was in contactwith the north pole acquiring south polarity. Alonger bar may be charged, by employing the sameprocess that has been described in 251, for touchingby steel magnets. 303. Bars of the U form are most readily mag-netized by drawing them from the bend to theextremities across the poles of the U-electro-magnet,in such a way that both halves of the bar may passat the same time over the poles to which they areapplied. This should be repeated several times,recollecting always to draw the bar in the samedirection. Then, if it has a considerable thickness,turn it in the hand, and repeat the process with itsopposite surface, keeping each half applied to thesame pole, as before. In Fig. 130, the arrow indi- Flg. cat^.s the direction in which the motion should takeplace. Of course, the result will be the same, ifthe steel bar is kept stationary, and the poles of 190 DAVISS the electro-magnet are passed over it in the re-verse direction. 304. In order to remove the magnetism of a steelmagnet of the U form, it is only necessary to reversethe process; that is, to place one of its poles on eachpole of the electro-magnet, and draw it over them inthe opposite direction to that of the arrow in In this way, the magnet may be so com-pletely discharged, as to be unable to lift more thana few iron filings. 305. A bar magnet may be deprived of its mag-netism, in a great degree, by passing the north poleof an electro-magnet over it, from its south pole toits middle, and then lifting it off perpendicularly ; if,then, the south pole be passed iii the same mannerover the other extremity of the steel bar, it will be
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
