Table 487 413 



EFFECT OF TENSION ON THE RESISTANCE OF METALS 



(Bridgman, Proc. Amer. Acad. Arts and Sci., 57, 41, 1922.) 



Generally hydrostatic pressure decreases the electrical resistance of metals. A few are 

 abnormal (see Table 485) — Bi, Li, Ca, Sr, Sb. Unit stress, kg/cm 2 . The tension coefficient 

 of specific resistance is obtained by subtracting (1 + 2<r)/E from the coefficient of observed 

 resistance. 



Supplementary Values to Table 484 



Resistance temperature coefficient for a number of metals and alloys of high purity 

 due to J. R. Caldwell (1931). 



Metal (Rioo— R<,)/iooR 



Ni 0.00667 



Zn 00419 



Cd 00423 



Pt 003925 



Rh 00436 



Alloy 

 95 Pt— 5 Rh 

 90 Pt— ioRh 

 80 Pt— 20 Rh 

 60 Pt— 40 Rh 

 40 Pt— 60 Rh 

 20 Pt— 80 Rh 



(i? 100 — R v )/iooR u 

 0.00215 

 O.OO169 

 O.OOI40 

 O.OOI44 

 O.OOI94 

 . 00260 



Note to Table 491, p. 417: Superconductivity. Apparent only below about io" K. ( — 263° C). The 

 following metals are known to show it below the indicated temperatures. A low current density is 

 necessary. 



Titanium i?7S K. 



Gallium 1 .05 



Niobium 8.2 



Molybdenum .... 1 . ? 



Indium 3°37 K. 



Tin 3.7 



Tantalum 4.4 



Mercury 4.22 



Thallium 2^7 K. 



Lead 7.2 



Thorium 1.5 



Some alloys 



Zn. Cd, Ge, Al, Pt, Na, Li do not show it. 



McLennan, Nature, 130, Dec. 10, 1932. Hill, Rev. Scientific Instr., 4, 3, 1933. 



Smithsonian Tables 



