. The practical telephone handbook and guide to the telephonic exchange . ass a velocity of 1 centimetre per second. A unit magneticpole is one which exerts a force of 1 dyne on a similar pole at adistance of 1 centimetre in air. If m and m represent thestrengths of two magnetic poles, and d the distance between them, then —-^— = /, the force in dynes of the attraction or repulsion between them in air. Magnets.—The simplest form of magnet is the straight bar magnet. Magnets of horse-shoe pattern, Fig. 4, are, how-ever, weight for weight, muchstronger, the poles being closer,and the lines of fo
. The practical telephone handbook and guide to the telephonic exchange . ass a velocity of 1 centimetre per second. A unit magneticpole is one which exerts a force of 1 dyne on a similar pole at adistance of 1 centimetre in air. If m and m represent thestrengths of two magnetic poles, and d the distance between them, then —-^— = /, the force in dynes of the attraction or repulsion between them in air. Magnets.—The simplest form of magnet is the straight bar magnet. Magnets of horse-shoe pattern, Fig. 4, are, how-ever, weight for weight, muchstronger, the poles being closer,and the lines of force clusteredtogether between them. Theyexert about three or four timesthe attractive power on a pieceof soft iron near their polesthat a bar magnet of the samesize would exert. Fig. 5 showsthe lines obtained when the cardon which the filings are spreadis laid on the ends of the poles N S. Thin bars or plates of steelcan be more powerfully mag-netised, in proportion to their weight, than larger masses;therefore when a strong permanent magnet is required it is ^v%. lg- INTRODUCTORY ii generally made up of several thin plates, producing what iscalled a compound or laminated magnet. The plates areusually bound together by pieces of soft iron, which form thepole-pieces. Some compound magnets have been made whichwould carry a load equal to twenty-five times their own best cast steel, with an addition of 3 per cent, of tungsten,makes the best magnet steel—the value of which depends uponwhat is called its retentivity, or its resistance to change in its <*■ mmmm
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelephone, bookyear19
