A manual of practical medical electricity - the Röntgen rays and Finsen light (1902) (14803511813)

Identifier: manualofpractica00turn (find matches)

Title: A manual of practical medical electricity : the Röntgen rays and Finsen light

Year: 1902 (1900s)

Authors: Turner, Dawson

Subjects: X-Rays Electrophysiology Electrosurgery Electric Stimulation Therapy Electrotherapeutics X-rays Electrophysiology Electrosurgery

Publisher: New York : William Wood & Company

Contributing Library: Francis A. Countway Library of Medicine

Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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wu ^ w> COo 15. < iJPi Current-Strength 71 would have a resistance of only one ohm, and ten Daniellsof half an ohm ; but as we have practically only one cell,so we get only the E. M. F. of one cell, viz., one volt. Asan example of the parallel arrangement, let us take oneDaniell cell with an internal resistance of five ohms, andan external resistance of two ohms ; then E I I 143 m.a. R+r 2+5 7 Now add on nine cells more in parallel ; the E. M. F. willremain the same, but the internal resistance will onlybe one-tenth of what it was. Thus : F T T :400 m.a. ; R + r 2-hTV 2-5 whereas we saw that ten such cells in series, with the sameexternal resistance, gave only 190 m.a. If we chose thecells best suited for cautery—e.g., with a low internal re-sistance, viz., bichromate or Groves—and coupled themin parallel, we should increase our current very much.Pass the current from one bichromate cell through anexternal resistance of two ohms, R+r~^ the E. M. F. of a bichromate is about t

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1902

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