182 ON FARADAY'S LINES OF FORCE. 



units delivered in unit of time, and K a quantity depending on the length 

 and resistance of the conducting circuit, then 



F=IK=p-p', 

 where p is the electric tension in the fluid and p' in the zinc. 



If the circuit be broken at any point, then since there is no current the 

 tension of the part which remains attached to the platinum will be p, and 

 that of the other will be p', pp' or F affords a measure of the intensity 

 of the current. This distinction of quantity and intensity is very useful *, 

 but must be distinctly understood to mean nothing more than this : The 

 quantity of a current is the amount of electricity which it transmits in unit 

 of time, and is measured by / the number of unit currents which it contains. 

 The intensity of a current is its power of overcoming resistance, and is 

 measured by F or IK, where K is the resistance of the whole circuit. 



The same idea of quantity and intensity may be applied to the case of 

 magnetism f. The quantity of magnetization in any section of a magnetic 

 body is measured by the number of lines of magnetic force which pass through 

 it. The intensity of magnetization in the section depends on the resisting 

 power of the section, as well as on the number of lines which pass through 

 it. If k be the resisting power of the material, and S the area of the section, 

 and / the number of lines of force which pass through it, then the whole 

 intensity throughout the section 



F T k 

 = f=I S' 



When magnetization is produced by the influence of other magnets only, 

 we may put p for the magnetic tension at any point, then for the whole 

 magnetic solenoid 



When a solenoidal magnetized circuit returns into itself, the magnetization 

 does not depend on difference of tensions only, but on some magnetizing force 

 of which the intensity is F. 



If i be the quantity of the magnetization at any point, or the number of 

 lines of force passing through unit of area in the section of the solenoid, then 



* Exp. Het. Vol. in. p. 519. t Exp. Res. (2870), (3203). 



