. The Ontario high school physics. direction, in what is known as the magneticmeridian^ wdiich is usually not far from the geographicalmeridian. That end of the magnet which points north is calledthe north-seeking, or simply the iV^-pole, the other the south-seeking or /S-23ole. 425. Magnetic Attraction and Repulsion. Let us bringthe /S-pole of a bar-magnet near tothe iV-pole of a compass needle(Fig. 446). There is an attractionbetween them. If we present thesame pole to the <S-pole of theneedle, it is repelled. Reversingthe ends of the magnet, we findthat its iV-pole now attracts the<S-
. The Ontario high school physics. direction, in what is known as the magneticmeridian^ wdiich is usually not far from the geographicalmeridian. That end of the magnet which points north is calledthe north-seeking, or simply the iV^-pole, the other the south-seeking or /S-23ole. 425. Magnetic Attraction and Repulsion. Let us bringthe /S-pole of a bar-magnet near tothe iV-pole of a compass needle(Fig. 446). There is an attractionbetween them. If we present thesame pole to the <S-pole of theneedle, it is repelled. Reversingthe ends of the magnet, we findthat its iV-pole now attracts the<S-pole of the needle but repels the iV-pole. We thus obtain the law:—Like magnetic poles repel, unlikeattract each other. This experiment can be repeated with very simple two sewing-needles by rubbing them, always in thesame direction, against one pole of a magnet. Then thrustthem into corks floating on the surface of water. On pushingone over near the other, the attractions and repulsions will bebeautifully Fig. 446.—The S-pole of one magnetattracts the .W-pole of another. MAGNETIC SUBSTANCES 369 It is to be observed tliat uninagnetized iron or steel Avill boattracted by both end; of a magnet. It is only wlien botiibodies are magnetized that we can obtain repulsion. 426. Magnetic Substances. A magnetic substance is onewhich is attracted by a magnet. Iron and steel are the onlysubstances which exhibit magnetic effects in a marked and cobalt are also magnetic, but in a much smallerdegree. In recent years Heusler, a German physicist, hasdiscovered a remarkable series of alloys possessing magneticproperties. They are composed of manganese (about 25 percent.), aluminium (from 3 to 15 per cent.) and copper. Thesesubstances taken singly are non-magnetic, but when meltedtogether are able easily to affect the magnetic needle. On the other hand, bismuth, and some other sub-stances are actually repelled by a magnet. These are said tobe di
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