408 



Tables 482 and 483 



TABLE 182 

 THE TRIBO-ELECTRIC SERIES 



In the following table it is so arranged that any material in the list becomes positively electrified when 

 rubbed by one lower in the list. The phenomenon depends upon surface conditions and circum- 

 stances may alter the relative positions in the list. 



Shaw, Pr. Roy. Soc. 94, p. 16, 1917; the original article shows the alterations in the series sequence 

 due to varied conditions. 



TABLE 483 



AUXILIARY TABLE FOR COMPUTING WIRE RESISTANCES 



For computing resistance in ohms per meter from resistivity, p, in michroms per cm. cube (see 

 Table 484, etc.). e. g. to compute for No. 23 copper wire when p= 1.724: 1 meter = 0.0387 + 

 .0271 -f- .0008 -f- .0002 = 0.0668 ohms ; for No. 1 1 lead wire when p = 20.4 ; 1 meter = 0.0479 + 

 .0010 = 0.0489 ohms. The following relation allows computation for wires of other gage num- 

 bers : resistance in ohms per meter of No. N = 2(« — 3) within 1 % : e.g. resistance of meter of 

 No. 18 = 2 XNo. 15. 



Smithsonian Tables. 



