Experiments with Open Circuits. 57 



^(L; + Mj + N&)==0. 



Integrating this equation from before the break till after, we 

 get, if there be no condenser in the primary, 



where 7 is the original current through the primary circuit ; 

 . L7-N& 

 J M 



Now, if the coil EF be open, k will be zero, or, at any 

 rate, very small ; for though from its electrostatic capacity 

 some current may exist in EF, yet, from the way EF is 

 wound, its electrostatic capacity must be small, so that ap- 

 proximately 



J M' 

 Now, when the coil EF is closed, 



._ L y -N£ 

 3 M ? 



where k is the current in the coil EF which is quite compa- 

 rable with 7; so that in this case j is much less than when the 

 coil EF was open; but if the coil EF has its extremities con- 

 nected with the plate of a condenser, then, again 



L7-N& 



J? = 



M 



Now in this case the current in the coil EF will be oscillatory, 

 so that h may have any values, positive or negative, within 

 certain limits. Thus, although the initial value of/ is perhaps 

 not much greater than when the coil EF is closed, yet after 

 h has completed a second oscillation and attained its maxi- 

 mum negative value, j will then not only be greater than when 

 the circuit EF is closed, but will be even greater than when 

 it is open. These theoretical conclusions agree with the expe- 

 riments mentioned above, which are examples taken at random 

 from a great number of experiments. 



If the secondary coil be open instead of closed, the phenomena 

 are by no means the same. It was found, under these circum- 

 stances, that the magnetization of a needle placed in the 

 secondary was much less intense when the coil EF was open 

 than when it was closed, which is exactly opposite to what 

 took place when the secondary was closed. The following 

 results, taken at random from many experiments, will show 

 how clearly this effect is marked. 



