THE PROPERTIES OF ELECTRICALLY 

 CONDUCTING SYSTEMS 



Chapter I. 

 Introduction. 



1. Classification of Conductors. The property of electrical con- 

 ductance appears to be one common to all forms of matter. The value 

 of the conductance of different forms of matter, however, varies within 

 very wide limits. Thus, the specific conductance of silver has a value 

 of 6.0 X 10 5 , while that of paraffin is 3.5 X 10~ 19 . The specific con- 

 ductance of gases under ordinary conditions is scarcely measurable. Nat- 

 urally, the conductance of any given system depends upon its state; and, 

 in general, any change in the condition of the system will materially 

 affect the value of its conductance. 



Conductors may be conveniently grouped into a number of classes, 

 the members of which possess many properties in common. 



2. Gases. Under ordinary conditions the conducting power of gases 

 is of a very low order, and such conductance as they possess is not an 

 intrinsic property of the gases themselves, but is due, rather, to the in- 

 fluence of external agencies. Thus, under the action of various radia- 

 tions, gases are ionized and when in this condition conduct the current. 

 This power of conduction, however, is lost when the external source of 

 excitation is cut off. Whether or not the gases themselves may possess 

 in some slight degree the power of conducting the current is uncertain, 

 since the conducting power of gases which have been entirely freed from 

 disturbing effects is of such a low order that the usual methods of meas- 

 urements fail. The conductance of a gas is a function of its density. 

 It is probable that at high densities gases will exhibit properties com- 

 parable with those of many liquids. In the case of hexane it has been 

 shown that the residual conductance on purification is for the most part 

 due to the action of external radiations, which indicates that the con- 

 ductance, which many liquid substances of low conducting power possess, 

 is not a property of the pure substances themselves. 



In gases, as well as in insulating liquids, under the action of external 



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