Tables 408, 409. 

 COPPER WIRE TABLES. 



TABLE 408. —Temperature Coefficients of Copper for Different Initial Temperatures (Centigrade) 



and Different Conductivities. 



335 



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



Rt=-Rti(i+atJt-tJ), 



where a. is the "temperature coefficient," and ti is the "initial temperature" or "temperature of reference." 



The values of a in the above table exhibit the fact that the temperature coefficient 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., il [>ercent 

 conductivity = 99 per cent, n =: 0.99.) 



I 

 «t. = ; . 



+ (/l — 20) 



« (0.00393) 



Smithsonian Tables. 



