522 Variation of Thermal Conductivity with Temperature. 



Silver (Wiedemann and Franz). 



*. 



0. 



/ iooo+e\ 

 MSooTe) 



log/(^)-log/(0") 



/(fl,.,)+/M 



»-l 



f{0n) 







= log/(0). 



=li%\oge. 



= 2 cosh fi%. 



194 



42 5 



17758 







167 



373 



17200 



•0558 a 



l-977 b 



142 



320 



1-6544 



•0607 



2024 



122 



27 5 



1-5893 



•0621 



2018 



104 



23-5 



1-5217 



•0635 



2 030 



88£ 



20-2 



1-4568 



•0638 



2036 



75* 



177 



1-3994 



0627 





a The mean of these numbers is "061 4; hence 



b The mean of these is 2-017; hence 

 li%= VW=1304. 



42. Although the whole investigation applies only to the 

 case of a long rod, yet it seems extremely possible that some- 

 thing very like the proper equation to the curve of tempera- 

 ture down a short rod with given temperature at its two ends 

 can be written down from equation (40) by the addition of 

 another term to the right-hand side, thus. 



O 7 ?±0 = Ae»* + Be-** i 

 r + U 



(45) 



just as the ordinary equation for an infinite rod 



e=%e-t" 



becomes 



d^Ae^+Beri" 



for a short one. If so, the conductivity-constant jjl and the 

 variation-constant m would be best determined from the rela- 

 tion 



/i m + 6 1 ra + a 



A 



m 



e, 



— const = 2 cosh fig 



[25] 



+ 2 



by some such process as is given in § § 23-25. 



The extent of the constancy of this quotient with Wiede- 

 mann's numbers is therefore exhibited in the last column of 

 the preceding tables; and the value of yaf is obtained from this 



