Resistance of Bismuth to Alternating Currents. 559 



As the angle of lag has already been found to be inde- 

 pendent of field-strength, it may now be safely said that the 

 angle of lag is a function of the frequency only. 



To find the relation between the magnitude of the bismuth 

 E.M.F. and temperature, the results given in fig. 7 were used; 

 but besides these it was found possible to get a measurement 

 of the magnitude only, every 10° between —90° and 0°, 

 by making use of the fact, just found, that the angle of lag is 

 independent of temperature. 



Fig. 8 gives the results of these experiments, and shows 



Fig. 8. 













































■CZi 

 •020 

 ■CIS 

 ■CIS 

 014 

 ■OK 

 ■010 

 •CCS 

 406 

 ■004 

 ■LZl 















































l-Kh 



FIEL 



■}UtN 



a st 



CY = 



RENC 



30 

 TH = 



7000 







» 







































/ 

 / 









































1 

 1 

























<ufrj 

















1 

























uJ 















/ 



























UJ 















/ 



























X 















/ 



























5 













1 





























CD 













t 

 / 







































• 

 • 





















V, 



V 























TEf/ 



PER. 



^TUP 



IE 





















-260 c -240°-P?0°-200° 



-160 -140 -120 -100 -80 -TO -40 -20 20 AO 60 80 100 



that the effect, which is small at —180° and 100°, becomes 

 comparatively large between, reaching a maximum at — 70°, 

 where with the small field of 7000 lines and a frequencv of 

 30 per sec. the bismuth E.M.F. is 2-2 per cent, of the E.M.F. 

 applied to the bismuth, being five times greater than its value 

 at ordinary temperatures. 



This variation of the bismuth E.M.F. with temperature is 

 most important, because it shows that the effect, if not due to 

 the Hall effect, has a close connexion with it, for a very 

 similar variation of the Hall effect with temperature has been 

 demonstrated by Dr. A. Lebret (' The Electrician/ vol. xxxvi. 

 1896, p. 785). 



In conclusion the results of the whole investigation may 

 be briefly stated : — 



I. The magnitude of the bismuth E.M.F. 



(a) is proportional to the current in the bismuth ; 



(b) is a linear function of the field-strength ; 



(c) increases with the frequency ; 



(d) varies with temperature, having a maximum value 



about — 70°, decreasing rapidly on either side. 



