Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . immuiflMjijiHimiBflirafflBnjiifflMifflnRmiffliD magnetic MAGNET REVOLVING IN A COIL. 217 SO supported as to revolve by the earths action ina horizontal plane, instead of a vertical one. In this Fig. 150. ifliBi. flrafliflmBWHHWTRmiwiiimHiHmniiiMuy] case, the instrument must beplaced in such a position thatthe polarity shall be reversedwhen the revolving mag-net assumes the direction ofthe compass-needle, pointingnorth and south, 346. When a steel mag-
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . immuiflMjijiHimiBflirafflBnjiifflMifflnRmiffliD magnetic MAGNET REVOLVING IN A COIL. 217 SO supported as to revolve by the earths action ina horizontal plane, instead of a vertical one. In this Fig. 150. ifliBi. flrafliflmBWHHWTRmiwiiimHiHmniiiMuy] case, the instrument must beplaced in such a position thatthe polarity shall be reversedwhen the revolving mag-net assumes the direction ofthe compass-needle, pointingnorth and south, 346. When a steel mag-net is placed in a proper po-sition near the revolving bar,^ ^ in either of the instruments whose motion depends on the earth^s influence, itrotates with much greater speed than by the actionof terrestrial magnetism alone. Its motion may bereversed, notwithstanding the opposing influence ofthe earth, by disposing the permanent magnet in asuitable manner. 347. Electro-Magnet revolving within a Coil,— Fig. 151 represents an instrument in which astraight electro-magnet revolves within a circular same current traverses the coil and the wire sur-rounding the rotating bar, but its direction is changedonly in the latter. When the circuit is completed,the revolving bar moves so as to bring its poles intoa direction corresponding with those of
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
