422 



Tables 497 and 498 

 COPPER WIRE 



TABLE 497. — Temperature Coefficients of Copper for Different Initial Temperatures (Centigrade) 



and Different Conductivities 



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



Rt=Rt 1 (i+o ti [t— tj), 



where a t 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 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, », 

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

 jonductivity = 99 per cent, n = 0.99.) 



n (0.00393) 



■f(A— 20) 



Smithsonian Tables- 



