An elementary book on electricity and magnetism and their applications . urn around by the at-traction of the magnetic field while the armature time the molecules are caused to turn around underthe influence of a magnetic field, a certain amount of poweris used, which is converted into heat; consequently, for everyrevolution of the armature a certain amount of power is usedand converted into heat. This is an effect of magnetism whichhas been described in Chapter V. The amount of power wasted and heat produced in a coreon account of hysteresis depends upon the amount of iron in t
An elementary book on electricity and magnetism and their applications . urn around by the at-traction of the magnetic field while the armature time the molecules are caused to turn around underthe influence of a magnetic field, a certain amount of poweris used, which is converted into heat; consequently, for everyrevolution of the armature a certain amount of power is usedand converted into heat. This is an effect of magnetism whichhas been described in Chapter V. The amount of power wasted and heat produced in a coreon account of hysteresis depends upon the amount of iron in the core, the numberof reversals per secondmade by the magnet-ism in it, the densityof magnetism in theiron, and the quality ofthe iron. It may besaid that, in genera1., thesofter the iron the lessis the loss due to hyster-esis; consequently, theiron used in armaturecores is very soft wrought iron or steel which lias been carefullyannealed. In modern machines the cores for armatures are built upof disks which are punched out of sheet iron (Fig. 153). These Wooden Wedge. Fig. 153. — Portion of laminated armature corewith air duets and insulated conductors. DIRECT-CURRENT GENERATORS 219 disks are sometimes insulated from each other by thin tissuepaper, or by thin coverings of varnish or nonconducting object of dividing the cores into disks, or laminating them,and of insulating the disks from each other is to preventeddy currents from being set up in the core itself when it isrevolved in the magnetic field. The rule that electric currentsare set up when a conductor cuts lines of force applies just asmuch to the core of the armature as to the windings. Currentstend to flow in armature cores from one end to the other nearthe surface under one magnet pole, and to return under theopposite pole. By properly laminating the cores these cur-rents are nearly all prevented, and at the same time the passageof lines of magnetic force through the iron from one side ofthe core to the
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
