Theory and calculation of alternating current phenomena . ules; loss of power per cubic centimeter at frequency, /, p = JW = e\N^B~ 10-7 = d\NW lO-i watts; total loss of power in volume, V, P = Vp ^ 7rf2/2J52 10-11 ^vatts. As an example, d = 1 mm., = cm.; / = 100; B^ = 5,000; V =1,000 cu. cm. Then, e = X 10-11,W = 1,540 ergs = joules,p = watts,P = watts, hence very much less than in sheet iron of equal Comparison of sheet iron and iron di = thickness of lamination of sheet iron, and di = diameter of iron wire. 142 ALTERNATING-CU
Theory and calculation of alternating current phenomena . ules; loss of power per cubic centimeter at frequency, /, p = JW = e\N^B~ 10-7 = d\NW lO-i watts; total loss of power in volume, V, P = Vp ^ 7rf2/2J52 10-11 ^vatts. As an example, d = 1 mm., = cm.; / = 100; B^ = 5,000; V =1,000 cu. cm. Then, e = X 10-11,W = 1,540 ergs = joules,p = watts,P = watts, hence very much less than in sheet iron of equal Comparison of sheet iron and iron di = thickness of lamination of sheet iron, and di = diameter of iron wire. 142 ALTERNATING-CURRENT PHENOMENAthe eddy current coefficient of sheet iron being €1=1^ di210-9,and the eddy current coefficient of iron wire 62 = ^ do. 10-«, the loss of power is equal in both—other things being equal—ifei = €2, that is, if f/2 = % ch^, or ^2 = It follows that the diameter of iron wire can be times or,roughly, 1^^ as large as the thickness of laminated iron, to givethe same loss of power through eddy currents, as shown in Fig. 93. 110. Demagnetizing, or screening effect of eddy currents. The formulas derived for the coefficient of eddy currents inlaminated iron and in iron wire hold only when the eddy currentsare small enough to neglect their magnetizing force. Other-wise the phenomenon becomes more complicated; the magneticflux in the interior of the lamina, or the wire, is not in phase withthe flux at the surface, but lags behind it. The magnetic fluxat the surface is due to the impressed , while the flux in theinterior is due to the resultant of the impressed and to of eddy currents; since the eddy currents lag 90 degreesbehind the flux producing them, their resultant with theimpressed , and therefore the magnetism in the interior,is made lagging. Thus, progressing from the surface towardthe interior, the magnetic flux gradually lags more and more inphase, and at the same time decreases in intensity. While thecomp
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectelectriccurrentsalte
