Electric Lighting and Power Distribution Volume 1; An Elementary Manual of Electrical Engineering (Paperback)

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. 1904 Excerpt: ...an immense amount of labour if worked out by ordinary multiplication and division. The reader is strongly advised to learn the use of tables of logarithms, which can be easily mastered: by their means such calculations as the above are greatly facilitated. Slide rules are also handy for carrying out arithmetical calculations, and present few difficulties in their application. Then the force in dynes by which they are attracted together will be: --To reduce to pounds, divide by the number of Having measured the force in pounds and the area, the induction can be calculated. This is the principle of Hopkinson's arrangement, and of Kapp's modification of and the original Thompson permeameter. Hughes, in his earlier experiments, balanced the moment of the electro-magnet (whose core of iron was being tested) by a large permanent magnet, which could be adjusted so as to bring a magnetic needle between the two to zero. The different ballistic methods depend upon the measurement of the induced quantity of electricity flowing round the circuit, on the reversal or change in the value of the current through the exciting coil: the quantity of electricity being proportional to the change in the induction. In practice, the ballistic method, with various modifications, has been largely used. Ewing's magnetic tester measures hysteresis directly, by the force exerted on a permanent magnet when the iron to be tested is rotated 1 g is tlio value (in dynes) of the gravitating force of unit mass (one gramme). It is equal to 981 dynes in England. ( 7.) between its poles. Dr. 0. V. Drysdale has recently invented a most practical form of permeameter, with which any piece of iron or steel, no matter what its bulk or shape, may be tested. Though this is probably the most difficu...