284 TABLES 316-322. 



WIRE TABLES. 



TABLE 316. Introduction. Mass and Volume Resistivity of Copper and Aluminum, 



The following wire tables are abridged from those prepared by the Bureau of Standards at the 

 request and with the cooperation of the Standards Committee of the American Institute of Elec- 

 trical Engineers (Circular No. 31 of the Bureau of Standards). The standard of copper resist- 

 ance used is "The International Annealed Copper Standard" as adopted Sept. 5, 1913, by the 

 International Electrotechnical Commission and takes the Resistivity at 20 C. of an annealed copper 

 wire one meter long weighing one gram as equal to o. 1 5328 ohm. This standard corresponds to 

 a conductivity of 58. X io~ 5 cgs. units, and a density of 8.89, at 20 C. 



In the various units of mass and volume resistivity this may be stated as 



The tern 

 However 



0.15328 ohm (meter, gram) at 20 C. 

 875.20 ohms (mile, pound) at 20 C. 

 1.7241 microhm-cm, at 20 C. 

 0.67879 microhm-inch at 20 C. 

 10.371 ohms (mil, foot) at 20 C. 



mperature coefficient for this particular resistivity is 820 = 0.00393 or 80 = 0.00427. 

 However, the temperature coefficient is proportional to the conductivity, and hence the change of 

 resistivity per degree C. is a constant, 0.000597 ohm (meter, gram). The "constant mass" tem- 

 perature coefficient of any sample is 



0.000597 -f 0.000005 



Et resistivity in ohms (meter, gram) at t C ' 



The density is 8.89 grams per cubic centimeter at 20 C., which is equivalent to 0.3212 pounds 

 per cubic inch. 



The values in the tables are for annealed copper of standard resistivity. The user of the 

 tables must apply the proper correction for copper of other resistivity. Hard-drawn copper 

 may be taken as about 2.7 per cent higher resistivity than annealed copper. 



The aluminum tables are based on a figure for the conductivity published by the U. S. Bureau 

 of Standards, which is the result of many thousands of determinations by the Aluminum Company 

 of America. A volume resistivity of 2.828 michrom-cm., and a density of 2.70 may be con- 

 sidered to be good average values for commercial hard-drawn aluminum. These values give : 



Mass resistivity, in ohms (meter, gram) at 20 C 0.0764 



" " (mile, pound) at 20 C 436. 



Mass per cent conductivity 200.7% 



Volume resistivity, in michrom-cm. at 20 C 2.828 



in microhm-inch at 20 C 1.113 



Volume per cent conductivity 61.0% 



Density, in grams per cubic centimeter 2.70 



Density, in pounds per cubic inch . . 0,0975 



SMITHSONIAN TABLES. 



