Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . the body will have a numberof intermediate poles and neutralpoints, which may be readilyshown by plunging its entire length f ,.into iron filings. Such inter- N\! (9/:--?vvS;^^/^^^/.omediate poles are called consequentpoles and arrange themselves asshown in Fig. 46. A bar thusmagnetised practically consists ofseveral magnets put together endto end, but in the reverse order Fi 46>_Consequent , SN, NS, etc. The nature of each pole can be tested, while it is attracting iron f
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . the body will have a numberof intermediate poles and neutralpoints, which may be readilyshown by plunging its entire length f ,.into iron filings. Such inter- N\! (9/:--?vvS;^^/^^^/.omediate poles are called consequentpoles and arrange themselves asshown in Fig. 46. A bar thusmagnetised practically consists ofseveral magnets put together endto end, but in the reverse order Fi 46>_Consequent , SN, NS, etc. The nature of each pole can be tested, while it is attracting iron filings,by bringing near it a bar magnet with some filings attractedto it. The attraction or repulsion between the filings can benoticed at a considerable distance. 41. Magnetic Screens.—Permit a magnet to deflect amagnetic needle from its N and S-position; the deflection isnot altered, if any non-magnetic substance be interposedbetween the needle and the magnet, such as a piece of wood,glass, or rubber, Fig. 47. The needles lines of force com-plete their circuit through the non-magnetic body to the mag-. MAGNETIC INDUCTION. 33 net, as shown in Fig. 47. A piece of iron, however, when inter-posed between the magnet and the needle, acts as a magneticscreen and reduces the deflection of the needle toward the mag-net. A needle, free to move, takes up a position in the earthsmagnetic field with its magnetic lines parallel with, and inthe same direction as the earths lines of force. When amagnet is approached to it, it assumes a position which isthe resultant of the two forces now acting upon it. No effectis produced by interposing a non-magnetic body, such as aboard, but when a piece of iron is interposed part of thelines of force of the magnet (Fig. 48) are now employed in .s To HQSSSlk&Poh vnif,- -/ ~S~\ & f >* ~-^ N, is N V _*? /
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