An international system of electro-therapeutics : for students, general practitioners, and specialists . ting the junction. For example, if a current be passed through a Bi-Sb junctionfrom Sb to Bi, the junction will be heated by disengagement of heat; ifthe current be passed in the opposite direction, from Bi to Sb, the junc-tion will be cooled by absorption of heat. There will be no difficulty in remembering these facts if it be remem-bered that, both in the Seebeck effect and in the Peltier effect, a currentfrom Bi to Sb is always attended with absorption of heat. 69. Neutral Point and Reve
An international system of electro-therapeutics : for students, general practitioners, and specialists . ting the junction. For example, if a current be passed through a Bi-Sb junctionfrom Sb to Bi, the junction will be heated by disengagement of heat; ifthe current be passed in the opposite direction, from Bi to Sb, the junc-tion will be cooled by absorption of heat. There will be no difficulty in remembering these facts if it be remem-bered that, both in the Seebeck effect and in the Peltier effect, a currentfrom Bi to Sb is always attended with absorption of heat. 69. Neutral Point and Reversal.—If we connect two Cu wires toa galvanometer and also wind their free ends around an iron wire, A B(Fig. 26), we can verify the following phenomena discovered by the junction, B, a current will go in the direction ^^, as shown bythe galvanometer. It will increase heat at a decreasing rate : when B isat 260° C. it will become steady, and then will decrease until at 500° C.(supposing A to be constant at 20° C.) it will become zero, and then willturn in the opposite A-48 DUFF. Now, it will be noticed that the temperature of reversal is as muchabove 260° C. as the temperature of A is below it. This would be trueno matter what the temperature of A. Thus, A being at 20 o (= 360 — 340°), reversal occurs at 500 o (= 260 + 240°). 100 O (=260 —160O), 420 o (= 360 + 160O). 250 o (=260— lOO), 270 o (=260+ 10°). 259JO(=260— ^O), 260|O(=260+ §0). Now, by remembering the definition of thermo-electric power at acertain temperature as the electro-motive force when one junction is halfa degree above and the other half a degree below that temperature, thelast result in the table is readily interpreted as meaning that at 260degrees the thermo-electric power of a Cu-Fe couple is zero, or the metalsare neutral to one another. Hence, 260 degrees is called the neutralpoint for an Fe-Cu couple. Similar results hold true for all other couples. Each coup
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectuterus, bookyear1894
