375 

 TABLES 370-406.— VARIOUS ELECTRICAL CHARACTERISTICS 



OF MATERIALS 



The fundamental electrical and magnetic definitions and the values of the 

 practical units of current, voltage, and other electrical quantities, have been 

 given (Tables 2-5). Some data will now be presented on electrical characteris- 

 tics of various materials. 



TABLE 370.— THE EFFECT OF ELECTRIC CURRENT ON THE 

 HUMAN BODY 18 "" 



Some thought must be given to the electrical characteristics of the human body, since 

 careless handling of electric circuits is very dangerous. The regular 120-volt circuit is dan- 

 gerous, and any voltage above this increases the hazard. No bare contacts should be per- 

 mitted where anyone might come in contact with them. 



AC (60 cycles) DC 



Threshold of perception 1 ma 5 ma 



muscular decontrol 15 <70 



danger to life 20 80 



fibrillation (almost certain death) 100 



Since the resistance of the human body for direct current (hand to foot or hand to hand), 

 neglecting the contact resistance, is 5,000-10,000 ohms, good contact with electric circuits 

 must be avoided. For alternating current the resistance is much lower. 



i3«a Cromwell, J. C, Origins and prevention of laboratory accidents, 1950; Bell Laboratories Rec, 



p. 318, June 1936; Johns Hopkins University, Report of Electrician, November 1934; Journ. 



Franklin Inst., vol. 215, p. 1, 1933. 



TABLE 371.— TRIBOELECTRICITY 



Part 1. — The tribo-electric series 



The following table is so arranged that any material in the list becomes positively elec- 

 trified when rubbed by one lower in the list. The phenomenom depends upon surface condi- 

 tions and circumstances may alter the relative positions in the list. 



1 Asbestos (sheet). 



2 Rabbit's fur, hair (Hg). 



3 Glass (combn. tubing). 



4 Vitreous silica, oppossum's 



fur. 



5 Class (fusn.). 



6 Mica. 



7 Wool. 



8 Glass (pol.), quartz (pol.), 



glazed porcelain. 



9 Glass (broken edge), ivory. 



10 Calcite. 



11 Cat's fur. 



12 Ca. Mg, Pb, fluorspar, 



borax. 



13 Silk. 



14 Al. Mn, Zn, Cd, Cr, felt, 



hand, wash-leather. 



15 Filter paper. 



16 Vulcanized fiber. 



17 Cotton. 



18 Magnalium 



19 K-alum, rock-salt, satin 



spar. 



20 Woods, Fe. 



21 Unglazed porcelain, sal- 



ammoniac. 



22 K-bichromate, paraffin, 



tinned-Fe. 



23 Cork, ebony. 



24 Amber. 



25 Slate, chrome-alum. 



26 Shellac, resin, sealing-wax. 



27 Ebonite. 



28 Co. Ni, Sn, Cu, As, Bi, 



Sb, Ag, Pd, C, Te, 

 Eureka, straw, copper 

 sulfate, brass. 



29 Para rubber, iron alum. 



30 Guttapercha. 



31 Sulfur. 



32 Pt. Ag, Au. 



33 Celluloid. 



34 Indiarubber. 



Part 2. — Triboelectric series in voltage of a number of metals as compared with 



silica (as O) I3e 



Au +17 Ni 



Pt + 15 Pb 



Ag +14 Fe 



Cd +10 Cr 



Cu + 9.3 Co 



Bi + 8.5 Tl 



13 " Shaw, P. E., and Leavey, E. W. L., 



Proc. Roy. Soc, vol. 138, p. 506, 1932. 



SMITHSONIAN PHYSICAL TABLES 



