Continuous-Current Dynamos in Theory and Practice; With Details of Methods and Formulae Used in Construction

Continuous-Current Dynamos in Theory and Practice; With Details of Methods and Formulae Used in Construction

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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. 1899 edition. Excerpt: ...sample of iron to be examined (which may be cast or wrought) has the form indicated in Fig. 1o3. To ensure exact measurements, the sections of the two magnetic circuits should be equal; moreover, the distance between the two branches should not be too small, on account of the magnetic leakage. On the middle branch are placed two bobbins--a large one, I., comprising as many turns as possible, and a small one, II., comprising two or three turns. The number of turns on the bobbin I. depends on the mean length, L, of the magnetic circuit and the strength of current employed. Suppose, for instance, that L = 5o cm., and that it is required to magnetise up to 19, ooo C.G.S. lines per square centimetre, the test piece being composed of cast steel; we shall require about 24o ampere-turns per centimetre length of the circuit, or altogether 24o x 5o = 12, ooo ampere-turns. If, therefore, the current strength is about 8o amperes, the bobbin I. should comprise. 15o turns. The resistance R is designed to vary the strength of the exciting current, the latter being read off from the ammeter, A. G is a ballistic galvanometer, calibrated by means of a condenser, so that the quantity of electricity discharged through it can be directly determined from the throw of the needle. The number of magnetic lines of force per square centimetre is determined by rapidly reversing the exciting current by means of a rocking commutator; the resistance Rx is employed to regulate the resulting throw of the galvanometer. Let 0 be the total number of lines of force traversing the section a; the alteration of this number due to the reversal of the exciting current is = + p-(-p) = 2 p. The corresponding quantity of electricity discharged through the galvanometer is therefore Q = where more

Product details

  • Paperback | 94 pages
  • 189 x 246 x 5mm | 181g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236599446
  • 9781236599445