Electricity and Magnetism

Electricity and Magnetism

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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. 1876 edition. Excerpt: ...has not been verified below o; hence the table must only be used to calculate E. M. F. for couples between o and 4000 or 5000 Centigrade. The metals used were not chemically pure. This table is calculated from the iron series in Prof. Tait's table, P-599-Proc. R.S.E. 1871-72, taking the E.m.f. of a Grove's cell as 1-93 volts. metals. Let nl and n2 be the temperatures of their neutral points with lead. Let tm be the mean temperature of the junctions; then the mean ordinate or m is given by the formula m = kx (nx-tm)-k2 (n2-tm) Thus, let the mean temperature of a pair of copper-iron junctions be 500, and the difference of the temperatures of the junctions ioo; then (50-f 68) (---0124) =--146 is one portion of the mean ordinate (for copper), and (5 357) (42) =--i2'9 is the other (for iron). Their difference is 1143, an tns multiplied into ioo gives 1143 as the E. M. F. of the copper-iron pair in microvolts. When the thermo-electric lines of two metals are nearly parallel, the E. M. F. produced by a pair of those metals will be nearly proportional to the difference of temperatures maintained between their junctions. For metals or alloys, the lines of which diverge, no such law even approximately holds good, and it is necessary, before the E. M. F. can be calculated, that we should know not only the difference of temperatures, but the actual temperatures of the junctions. 8. Anumber of thermo-electric pairs, or elements, maybe joined in series, so as to give an E. M. F. which is the sum of the electromotive forces of all Fi-. 90. the elements. To do this it is only necessary to join the metals, as shown in Fig. 90, and keep all the junctions on one side, as at A, warm while the, other side is cold..BatteriesJ of this kind are easily made...
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Product details

  • Paperback | 120 pages
  • 189 x 246 x 6mm | 227g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236545257
  • 9781236545251