The properties of the carbon pile are mentioned here. The resistance R is approximately given in the form R=nC/P
m; where n is the number of carbon piles C & m are the constants and P is the applied force. The resistance of the carbon pile having 1/N times the above area can be calculated by the formula R= (nCN
1-m) /P
m. If we decrease the compressive force from the maximum value P
max to the lower value P. then the car bon discs expand by the amount χ. There exists the following relation between them; P=P
max10
-χ/nk, where k is a constant. And the method of measuring the resistivity, perpendicular to the surface is mentioned.
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