Electricity and Magnetism for Engineers; Electric and Magnetic Circuits
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 edition. Excerpt: ...the flux density B as ordinates and the distance x as abscissas, (c) What is the relation between the area of this curve and this total flux? Answer.--(a) 3.18 X 106 lines, (c) The flux per pole is equal to this area multiplied by the length of the armature, which in this case is 8 inches. 88. Magnetomotive Force and Magnetic Reluctance.--The magnetic fields in most electric machinery and apparatus are due directly to electric currents.2 The relation between the magnetic l Such a "sinusoidal" distribution of flux is seldom actually realized in practice, but is often closely approximated, particularly in alternatingcurrent machines. s The magnetic fields of so-called permanent magnets will be considered in detail later; Article 104. flux produced by an electric current and the intensity of this current is, therefore, one of fundamental importance. The relation in question is of the same general form as that between an electromotive force and the current which it produces. Consider, for example, the magnetic field due solely to a current i in a single coil of N turns. The space in which the magnetic field exists may be thought of as divided into a number of closed rings, such as the ring M in Fig. 49, each ring being of such a shape that its walls are tangent at each point to the line of force through that point. Such rings will not in general be of a simple shape, and the cross-section of any particular ring at various points along its axis will not in general be the same. Since the walls of such a ring as that described are tangent at each point to the line of force through that point, no line of force can enter or leave it through its walls. Therefore every line of force inside such a volume must be a closed loop intersecting every...
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