Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . 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 up
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . 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 _*? /. Fig. 47.—Needle Deflected Through Non-Magnetic Body. magnetising the iron plate by induction. The needle pro-duces a similar effect on the other side of the plate, and beingfree to move, deflects slightly, until its lines of force are pro-portionately accommodated between the earths magnetismand the magnetism of the iron plate. When a thick ironplate is used it forms a perfect shield to the needle againstthe action of the bar magnet. If a compass needle wereplaced in the centre of a thick iron sphere it would beentirely screened from any external magnetism. This prin-ciple is utilized in the manufacture of heavy cast-iron boxes3 34 PRACTICAL ELECTRICITY. for measuring instruments which are to be placed on switch-boards near magnetic fields. Watches are often inclosed ina hunting case made of soft iron to protect their steel mainsprings from becoming magnetised from any cause. Should K vA M !? %
Size: 901px × 2774px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyo, bookyear1901
