Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . ring theentire revolution, and no sparks appear, as withthe spur-wheel. 185. De la Rives Ring. — A coil of wire, whiletransmitting the electric current, exhibits the samereactions with a magnet as the straight wire in 65. 6 land 62; but the circular directionin which the cur-rent flows gives tothe coil an appa-rent magnetic po-larity. This factmay be shown bymeans of the appa-ratus figured in theadjoining cut. Oneend of the wireforming the
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . ring theentire revolution, and no sparks appear, as withthe spur-wheel. 185. De la Rives Ring. — A coil of wire, whiletransmitting the electric current, exhibits the samereactions with a magnet as the straight wire in 65. 6 land 62; but the circular directionin which the cur-rent flows gives tothe coil an appa-rent magnetic po-larity. This factmay be shown bymeans of the appa-ratus figured in theadjoining cut. Oneend of the wireforming the coil,or helix, C, is sol-dered to a very small plate of copper, c, and the otherto a similar plate of zinc, z. These plates are fast-ened to a small piece of wood, in order to keep themapart, and placed in a little glass cup, D. To putthe instrument in action, a sufficient quantity ofwater, acidulated by a few drops of sulphuric ornitric acid, is poured into the glass cup to cover theplates, and the whole apparatus is floated in a basinof water. The coil will now be found to place itselfwith its axis north and south, being influenced by. 116 DAVISS MANUAL. the polarity of the earth, like a compass needle. Thearrow indicates the course of the galvanic current inthe coil from the copper to the zinc. 186. Take a bar magnet, M, and, holding it hori-zontally, bring its north pole near to the south poleof the ring. The ring will move towards the mag-net, and pass over it until it reaches its middle, whereit will rest in a state of equilibrium; returning to thisposition, if moved towards either pole and then leftat liberty. Now, holding the ring in its position,withdraw the magnet, and pass it again half waythrough the coil, but with its poles reversed. Thering, when set at liberty, will, unless placed exactlyat the centre, move towards the pole which is near-est, and, passing on till clear of the magnet, willturn round and present its other face. It will thenbe attracted, and pass
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
