RELATION BETWEEN THE VARIATION OF RESISTANCE IN BISMUTH. 



243 



It may be stated that for weak fields the method here given for measuring the resist- 

 ance is not suitable. For such the Wheatstone bridge or the differential galvanometer 

 would give good results in less time. 



Of the different plates used, only one was known to be perfectly pure. With it the 

 following results were obtained : — 



Length, . 

 Breadth, . 

 Thickness, 



16-75 | 



7-2 -: 



Temp. 10° C. w='9521 



c,= -E 



J An 



Field in 

 cgs. Units. 



Transverse 

 Effect. 



a 



An 



jAn 



An 



J An 



y 



An 



JAn 



a 



P 



y 



8,500 



-•2311 



•2949 



•5420 



•3144 



•5648 



•1489 



•3858 



-•42 



-•41 



-•60 



9,500 



- -2455 



•3292 



•5738 



•3556 



•5963 



•1622 



•4027 



-•42 



-•41 



-•60 



11,700 



- -2627 



•4001 



•6325 



•4333 



•6582 



•1780 



•4219 



-•41 



-•40 



-•62 



12,840 



- -2708 



•4552 



•6747 



•4717 



•6768 



•2066 



•4545 



-•40 



-•40 



-•59 



14,170 



- -2974 



•4815 



•6932 



•5258 



•7251 



•2357 



•4855 



-•42 



-•40 



-•61 



15,600 



- -3071 



•5881 



•7669 



■5684 



•7539 



•2500 



•5000 



-•40 



-•40 



-•61 



17,800 



- -3271 



•6281 



•7926 



•6252 



•7907 



•2704 



•5389 



-•41 



-•41 



-•60 



The relation between the transverse effect and the variation of resistance is a simple 

 one. The constants obtained for the positions a and /3 are the same : that for y is 

 different ; but it is to be remembered that the results given above depend upon the form 

 of the plate and upon the external resistance inserted in the galvanometer circuit, which 

 differed in position y from that in a and ft. To eliminate the various disturbing effects 



the quantity J should be used in equation (1) instead of ^ An. 



The two next plates were made from different supplies of commercial bismuth. 

 In them the numerical value of the transverse effect did not reach a maximum with the 

 fields at disposal. 



In Plate II. the simple relation (1) no longer applies ; the equation (2) was therefore 

 used. 



The average values of the constants c x and c 2 were obtained by solving the equations 

 obtained from combining the results for each field with those for every other ; the two 

 results immediately before and after were in each case rejected : — that is, with twelve 

 different field strengths, 1 . . . 12, we get eleven equations by combining result 6 say 

 with all others, but of these those derived from 5 and 7 were rejected. 



