Page:On Faraday's Lines of Force.pdf/28

182 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 $$p', p=p'$$ 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 $$I$$ 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. 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 $$I$$ the number of lines of force which pass through it, then the whole intensity throughout the section

$=F=I\frac{k}{S}$.

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

$=F=I \int_{}{}\frac{k}{S}dx=IK=p-p'$.

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