TABLE 376.— THERMOELECTRIC EFFECT OF ALLOYS 



379 



The thermoelectric effect of a number of alloys is given in this table, the authority 

 being Ed. Becquerel. They are relative to lead, and for a mean temperature of 50° C. In 

 reducing the results from copper as a reference metal, the thermoelectric effect of lead to 

 copper was taken as — 1.9. 



OH- > 



E*2 



Substancr 



Antimony 



Cadmium 



Antimony 



Cadmium 



Zinc 



Antimony 



Cadmium 



Bismuth 



Antimony 



Zinc 



Antimony 



Zinc 



Bismuth 



Antimony 



Cadmium 



Lead 



Zinc 



Antimony 



Cadmium 



Zinc 



Tin 



121 



227 



146 



95 



76 



46 



Substance 

 Antimony 

 Zinc 

 Tin 



Antimony 

 Cadmium 

 Zinc 



Antimony 

 Tellurium 

 Antimony 

 Bismuth 

 Antimony 

 Iron 



Antimony 

 Magnesium 

 Antimony 

 Lead 

 Bismuth 

 Bismuth 

 Antimony 



2 1 



1 } 43 



ll 



121 

 m I* 



35 



10.2 



8.8 



2.5 



1.4 



- .4 

 —43.8 

 -33.4 



Substance 



Bismuth 



Antimony 



Bismuth 



Antimony 



Bismuth 

 Antimony 



Bismuth 

 Antimony 



Bismuth 

 Tin 



Bismuth 

 Selenium 



Bismuth 

 Zinc 



Bismuth 

 Arsenic 



Bismuth 

 Bismuth sulfide 





12 

 1 



2 



1} 



51.4 

 63.2 

 68.2 

 -66.9 

 60 



-24.5 

 31.1 

 -46.0 

 68.1 



TABLE 377.— THERMOELECTRIC EFFECT 



A measure of the thermoelectric effect of a circuit of two metals is the electromotive 

 force produced by 1°C difference of temperature between the junctions. The thermoelectric 

 effect varies with the temperature, thus : thermoelectric effect = Q = dE/dt = A -f Bt, 

 where A is the thermoelectric effect at 0°C, 5 is a constant, and / is the mean temperature 

 of the junctions. The neutral point is the temperature at which dE/dt = 0, and its value 

 is — A IB. When a current is caused to flow in a circuit of two metals originally at a 

 uniform temperature, heat is liberated at one of the junctions and absorbed at the other. 

 The rate of production or liberation of heat at each junction, or Peltier effect, is given 

 in calories per second, by multiplying the current by the coefficient of the Peltier effect. 

 This coefficient in calories per coulomb = QT/J, in which Q is in volts per degree C, T is 

 the absolute temperature of the junction, and J = 4.19. Heat is also liberated or absorbed 

 in each of the metals as the current flows through portions of varying temperature. The 

 rate of production or liberation of heat in each metal, or the Thomson effect, is given in 

 calories per second by multiplying the current by the coefficient of the Thomson effect. 

 This coefficient, in calories per coulomb = BT6I J, in which B is in volts per degree C, 

 T is the mean absolute temperature of the junctions, and 6 is the difference of temperature 

 of the junctions. (BT) is Sir W. Thomson's "Specific Heat of Electricity," The algebraic 

 signs are so chosen in the following table that when A is positive, the current flows in the 

 metal considered from the hot junction to the cold. When B is positive, Q increases 

 (algebraically) with the temperature. The values of A, B, and thermoelectric effect in the 

 following table are with respect to lead as the other metal of the thermoelectric circuit. 

 The thermoelectric effect of a couple composed of two metals, 1 and 2, is given by sub- 

 tracting the value for 2 from that for 1 ; when this difference is positive, the current flows 

 from the hot junction to the cold in 1. In the following table, A is given in microvolts 

 per degree, B in microvolts per degree per degree, and the neutral point in degrees. 



The table has been compiled from the results of Becquerel, Matthiessen and Tait ; in 

 reducing the results, the electromotive force of the Grove and Daniell cells has been taken 

 as 1.95 and 1.07 volts. The value of constantan was reduced from results given in Landolt- 

 Bornstein's tables. 



(continued) 



SMITHSONIAN PHYSICAL TABLES 



