284 Sub-Lieut. A. L. Williams on the Electrical 



Two different samples of copper and mica were tested in 

 the furnace for variation in resistance with temperature (but 

 only up to about 400° C.). In Case No. 1 (Graph No. 3), 

 the resistance was found to vary from 4400 ohms to 300 ohms, 

 while the temperature varied from 25° G. to 400° C. The 

 specific gravity of the specimen was found to be 5*1, and as 

 copper is given by 8*9, it will be seen that the specimen 

 contained considerable mica. 





Gkaph No. 3. 





perature, 



Resistance 



Temperature, 



Resistance 



°0. 



(Ohms). 



°0. 



(Ohms). 



22 



4,400 



148 



1,250 



46 



3,600 



154 



1.150 



54 



3,200 



164 



1,100 



58-5 



2,940 



206 



780 



61 



2,900 



260 



611 



655 



2,800 



275 



450 



70 



2,460 



315 



400 



72 



2,400 



344 



340 



93 



1,950 



364 



281 



127 



1,550 







In Case No. 2 (Graph No. 4) the variation in resistance 

 was from 95,000 ohms to 3000 ohms, while the temperature 

 changed from 100° C. to 400° C. The specific gravity was- 

 found to be 4*3. 





Graph No. 4. 





Temperature, 



Resistance 



Temperature, 



Resistance 



°0. 



(Ohms). 



°C. 



(Ohms). 



139 



45,550 



228 



11,370 



178 



23,330 



211 



13,585 



236 



11,645 



208 



14,570 



262 



9,120 



200 



16738 



314 



6,000 



192 



19,090 



345 



4,590 



172 



23,445 



364 



3,790 



165 



26,230 



378 



3,605 



155 



29,670 



395 



3,280 



147 



34,050 



333 



4,200 



139 



40,505 



323 



4.740 



130 



44,350 



313 



5,490 



122 



51,340 



290 



6,330 



118 



57,110 



278 



7,030 



113 



64,070 



267 



7,790 



108 



74,033 



256 



8,610 



103 



81,740 



245 



9.410 



99 



91,010 



232 



10 790 







From these results it would appear that an increase in the 

 mica-content of the mixture raises the resistance at ordinary 



