An elementary book on electricity and magnetism and their applications . parated from it, the magnetism of thesoft iron disappears. It was Dr. Gilbert whoobserved that the attractive power of a magnet appears toreside in two spots or regions; in a long-shaped magnet thesespots or poles are usually near its ends. When a magnet issuspended on a pivot or a thread, it sets itself in a direction soas to point nearly north and south. A small elongated magnetthus suspended is called a magneticneedle or compass (Fig. 68). The pole which points towardthe north is called the north-seek-ing {N) pole and
An elementary book on electricity and magnetism and their applications . parated from it, the magnetism of thesoft iron disappears. It was Dr. Gilbert whoobserved that the attractive power of a magnet appears toreside in two spots or regions; in a long-shaped magnet thesespots or poles are usually near its ends. When a magnet issuspended on a pivot or a thread, it sets itself in a direction soas to point nearly north and south. A small elongated magnetthus suspended is called a magneticneedle or compass (Fig. 68). The pole which points towardthe north is called the north-seek-ing {N) pole and the other, thes nth-seeking (S) pole. 87. How to make a the steel must be do this, heat to brilliant redand then quickly plunge into coldwater, oil, or mercury. The steel then becomes intensely brit-tle and A very simple method of magnetizing thesteel is by stroking it with another magnet. It is better tostroke one half with an f>-pole, beginning at the center andrepeating this several times on each side; then using the. Fig. 68. — Magnetic needle in acompass. Black end is north-seeking. NATURE AND PROPERTIES OF MAGNETISM 121 iV-pole, stroke the other half in the same way. In these daj^swhen electricity is so common, it is more usual to magnetizesteel by making it a part in the magnetic circuit of an electro-magnet, as explained in Chapter IV. Tapping the end of thesteel with a hammer while it is under the influence of theelectric current will produce better results. 88. Forms of magnets. When steel bars, round or flat,are made into straight magnets, they are called bar a straight bar of steel is bent into the form of a horseshoe(Fig. 69) and then properly magnetized, oneend will be an JV-pole and the other an S-pole. By thus bringing the poles closetogether, the magnet will lift much morebecause both poles act together. A pieceof soft iron, called the keeper or armature,is placed across the ends of the poles whenthey are
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
