Magnetic Poles

—1. The ends ot a magnet, where the attractive force is greatest. In the bar magnet that end which tends to point north is called the north or positive pole, and the other the south or negative pole. 2. Those points on the earth’s surface, in neighborhood of the geographic poles, where dipping needle would stand vertical. 3. A unit magnetic pole is one of such a strength that, when at a distance of one centimeter from a similar pole of equal strength, it will repel it with a force of one dyne. The relation between magnetic poles may be expre ed by the ecuation: _ mX int f= d? in which f is the force in dynes, m and m! tue strengths of the two poles, and d? the distance between them in centimeters.