Eutherfoed. — On the Magnetization of Iron. 505 



The maximum currents flowing in the two branches are 

 proportional to the quantities under the roots, and it will be 

 observed that the distribution of current for high frequencies 

 depends more on the self-inductance than on the resistance of 

 the circuit. 



The two circuits were wound exactly equal to one another. 

 Each consisted of a solenoid of 34 turns, 22cm. long, 2-2cm. 

 in diameter. The wire was indiarubber-covered copper wire 

 O039in. in diameter. 



When a metal core is introduced into the solenoid and a 

 discharge passed there are vigorous induced currents in the 

 cylinder. When it is considered that a current of sometimes 

 100 amperes is reversed 10,000,000 times per second, the 

 induced currents must be large. These induced currents, on 

 account of the very short time which they last, are confined 

 to a thin skin of the cylinder. But these induced currents 

 tend to diminish the effective inductance of the circuit. The 

 amount of energy absorbed in the cylinder depends on the 

 difference of phase between the direct and induced currents. 

 The impedance of the circuit is given by v/B' 3 +£> 2 L 2 , and it 

 is of interest to know whether this is increased or decreased 

 by the introduction of a metal core. 



(1.) A copper cylinder 1cm. in radius was introduced into 

 one solenoid. By the use of an ordinary detector it was found 

 that more current flowed in the branch in which the copper 

 cylinder was placed than in the other branch. The amount 

 of current in one branch was 8 per cent, more than in the 

 other. Now, from the expressions given for the distribution 

 of current in each branch, it will be seen that the denomi- 

 nators of the expressions are the same, and the numerators 

 represent the impedances of the circuits. The value of 

 •v/R 2 + j p 2 L' 2 is decreased by about 8 per cent, by the introduc- 

 tion of the copper cylinder, or the effect of a copper core is to 

 diminish the impedance of the circuit. 



(2.) When a lead cylinder was introduced in place of the 

 copper no effect of unequal distribution could be with cer- 

 tainty detected. 



(3.) Magnetic Cylinders. — (a.) When a solid soft -iron 

 cylinder was introduced into the solenoid the current in that 

 branch was diminished by about 3 J per cent, (b.) Laminated 

 soft-iron wires placed in test-tube and thoroughly insulated 

 from one another decreased the current in its branch by more 

 than 12 per cent, (c.) Steel filings in a test-tube also de- 

 creased the current in its branch. 



The effect of iron, whether solid or finely divided, is there- 

 fore to increase the impedance of the circuit. 



This is the general result obtained for a frequency of about 



