404 TABLES 416-428.— ELECTRICAL AND MECHANICAL 

 CHARACTERISTICS OF WIRE 



TABLE 416.— INTRODUCTION TO WIRE TABLES; 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 Electrical Engineers. The standard of copper resistance used is "The Inter- 

 national Annealed Copper Standard" as adopted September 5, 1913, by the International 

 Electrotechnical Commission and represents the average commercial high-conductivity 

 copper for the purpose of electric conductors. This standard corresponds to a conductivity 

 of 58X10"" 6 emu, and a density of 8.89, at 20°C. In the various units of mass resistivity and 

 volume resistivity this may be stated as 



0.15328 ohm (m,g)at20°C 



875.20 ohms (mi, lb) at20°C 



1.7241 microhm-cm at 20°C 

 0.67879 microhm-in. at20°C 



10.371 ohms (mil, ft) at 20°C 



The temperature coefficient for this particular resistivity is a 20 = 0.00393, or a = 0.00427. 

 The temperature coefficient of copper is proportional to the conductivity, so that where the 

 conductivity is known the temperature coefficient may be calculated, and vice versa. Thus 

 the next table shows the temperature coefficients of copper having various percentages of 

 the standard conductivity. A consequence of this relation is that the change of resistivity 

 per degree is constant, independent of the sample of copper and independent of the tem- 

 perature of reference. This resistivity-temperature constant, for volume resistivity and 

 Centigrade degrees, is 0.00681 microhm-cm, and for mass resistivity is 0.000597 ohm (m, g). 

 The density of 8.89 g per cm 3 at 20°C, is equivalent to 0.32117 lb per in. 3 

 The values in the following 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 percent higher resistivity than annealed copper. _ 



The following is a fair average of the chemical content of commercial high conductivity 

 copper : 



Copper 99.91% Sulfur 002% 



Silver 03 Iron 002 



Oxygen 052 Nickel trace 



Arsenic 002 Lead 



Antimony 002 Zinc 



The following values are consistent with the data above : 



Conductivity at 0°C, in emu 62.969 X lO" 6 



Resistivity at 0°C, in microhm-cm 1.5881 



Density at 0°C 8.90 



Coefficient of linear expansion per degree C 000017 



"Constant mass" temperature coefficient 

 of resistance at 0°C 00427 



The aluminum tables are based on a figure for the conductivity published by the National 

 Bureau of Standards, which is the result of many thousands of determinations by the 

 Aluminum Co. of America. A volume resistivity of 2.828 microhm-cm and a density of 

 2.70 may be considered to be good average values for commercial hard-drawn aluminum. 

 These values give : 



Conductivity at 0°C in emu 38.36 X 10" 5 



Mass resistivity, in ohms (m, g) at 20°C 0764 



' (mi, lb) at 20°C 436. 



Mass percent conductivity relative to copper 200.7% 



Volume resistivity, in microhm-cm at 20 C 2.828 



in microhm-in. at 20°C 1.113 



Volume percent conductivity relative to copper 61.0% 



Density, in g/cm s 2.70 



Density, in lb/in. 8 0975 



The average chemical content of commercial aluminum wire is 



Aluminum 99.57% 



Silicon 29 



Iron 14 



SMITHSONIAN PHYSICAL TABLES 



