ELECTRICAL RESISTANCE UNDER PRESSURE. 



119 



relation between pressure and resistance is nearly linear, and the 

 departure is in the normal direction, that is, the coefficient becomes 

 less at the higher pressures. The results are somewhat unusual in 

 that the pressure coefficient does not advance regularly with increas- 

 ing temperature, but is less at 50° than at either 0° or 100°. The 

 same behavior was shown by the impurer sample also, and is doubtless 

 real. The departure from linearity is also less at 50° than at either 

 0° or 100°. 



20" 40' 60" 80' lOO' 



0'-' 20" 40 60° 80" 100° 



Temperature 



Tungsten 



2 4 6 8 10 



Pressure, Kg. / Cm.' X 10' 



Figure 9. Results for the measured resistance of tungsten. The devia- 

 tions from Unearity are given as fractions of the resistance at kg. and 0°C. 

 The pressure coefficient is the average coefficient between and 12000 kg. 



The results for the impurer sample were similar, but the numerical 

 values were different. The average coefficients to 12000 at 0°, 50°, and 

 100° being respectively - 0.0 51387, 1331, and 1362. These may be 

 compared with the values of the Table; the differences are of the 

 order of 0.5% at 50° and 100°, but the difference rises to 3% at 0°. 

 At 0° the coefficient of the impurer is larger, and at the two other 

 temperatures is smaller. 



These results may be compared with those recently published by 

 Beckman.^^ He finds for the average temperature coefficient of his 

 sample 0.00399, which is a trifle higher than that of the impurer sample 

 above. His initial pressure coefficient at 0° is — O.OslSl, reduced 

 from atmospheres as the pressure unit to kg/cm-. This value is 

 2.7% higher than that of the impurer of the two samples above, and 

 5.6% higher than that of the purer. A comparison of the present 

 results with my former ones shows that both of my new samples. 



