ELECTRICAL RESISTANCE OF NICKEL AT HIGH TEMPERATURES. 



Table D. — continued. 

 Diameter = -0396 cm. Specific resistance = 10680 (C.G.S.). 



Resistance of Resistance reduced 



191 



Temperature 



76°-5 C. 



99° 



120°-4 



144° 



165° 



184°-5 



204° 



226° 



247° 



268°-5 



291°-5 



305° 



Wire used. 

 2-02 ohms 

 2-146 

 2-265. 

 2-39 

 2-508. 

 2-607 

 2-72 

 2-832 

 2-94 

 305 

 3-163 

 3-216 



for comparison. 

 126-7 

 134-6 

 142-0 

 149-9 

 157-3 

 163-5 

 170-5 

 177-6 

 184-4 

 191-2 

 198-3 

 201-3 



A glance at the columns of reduced resistances, or at the representative 

 curves, shows at once one peculiarity of nickel as compared with the other 

 metals, namely, the comparatively great increase of resistance throughout the 

 measured range of temperature. The curves further show, by the manner of 

 their curvature, that the rate of increase of resistance of a given nickel wire per 

 degree centigrade increases as the temperature rises ; whereas this rate of in- 

 crease diminishes in the case of platinum and palladium. The same fact is readily 

 shown from the numbers themselves by dividing the successive first differences 

 of either column of resistances by the corresponding temperature differences. 



The impossibility of representing the march of the nickel resistance by an 

 empirical formula of ascending powers of the temperature has been already 

 noticed. Some mode of formulating the results is, however, advisable, so as to 

 make them numerically comparable with the results for platinum and palladium, 

 which can be represented very approximately in the usual way. The following 

 mode seems to be in many respects suitable : — 



First, calculate by strict interpolation methods from five contiguous observa- 

 tions, the resistances corresponding to successive conveniently chosen tempera- 

 tures, say, 0°, 50°, 100°, 150°, 200°, and 250°. Then tabulate, as in the sub- 

 joined table, the successive differences of these resistances. In the series of 

 2nd differences we recognise at once the impossibility of applying a parabolic 

 equation to the results for nickel. 



Table of Successive Differences of Thick Nickel Resistances. 



Temperature. 



Resistance. 



1st Differences. 



2nd Differences. 



0° 



•724 



-168 





50° 



•892 



-184 



-016 



100° 



1-076 



-219 



-035 



150° 



1-295 



-243 



-024 



200° 



1-538 



-287 



-044 



250° - 



1-825 





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