Tables 317,318. 285 



WIRE TABLES. 

 TABLE 317.— Temperature Ooefliclents ol Copper for Different Initial Temperatures (Centigrade) 

 and Different Conductivities. 



Note. — The fundamental relation between resistance and temperature is the following: 



Rt = Rti(l+ajJt — t,]), 



where aj is the "temperature coefficient," and tj is the "initial temperature" or "temperature of reference." 



The values of a in the above table exhibit the fact that the temperature coeflicient of copper is proportional to the 

 conductivity. The table was calculated by means of the following formula, which holds for any per cent conductivity, n, 

 within commercial ranges, and for centigrade temperatures. (« is considered to be expressed decimally: e.g., if percent 

 conductivity = 99 per cent, » = 0.99.) 



« (0.00393) 



+ (/i — 20) 



Smithsonian Tabucs* 



