THERMO-ELECTRIC QUALITY UNDER PRESSURE. 



323 



The pressure eflfects on Peltier heat and Thomson heat are both 

 positive, and both increase reguhirly with pressure and temperature. 

 At constant pressure the Thomson heat is proportional to absolute 

 temperature. 



Wagner found between 0° and 100° and up to 300 kg. + 4.6 X lO"'^ 

 volts per degree per kg. The value indicated by interpolation of the 

 data above is 5.3 X 10"^^. 



Copper. This was electrolytic copper from the same length of 

 wire as that whose resistance was measured under pressure, but not 



60° 

 Temperature 

 Copper 



Figure 21. Copper. Thermal E.M.F. of a couple composed of one branch 

 of uncompressed metal, the other compressed to the pressure in kg./cm.^ 

 indicated on the curves, the junctions being 0°C and the temperature plotted 

 as abscissae. 



the identical piece of wire. It was drawn down to 0.028 inch in 



diameter through steel dies, annealed to redness, and the surface 



rubbed off with emery paper. 



At atmospheric pressure its thermo-electric behavior against lead 



is given by the formulas: 



E = {2.1111 + 0.00483^2) X 10-« volts, 



P = (2.777 + 0.00966 {t + 273) X 10-« volts, 



a ^ 0.009G6(/ + 273) X 10"^ volts/°C. 



