8 Mr. A. W. Porter. On the Flow in Electric [June l r 



A and B are initially closed ; a steady current, # , flows in conse- 

 quence through L, and the condenser is charged to a difference of 

 potential R# . The pendulum breaks contact first at B. This, pre- 

 vents further flow in the battery branch ; the coil current is diverted 

 into the condenser branch, and flows there until its energy is wholly 

 dissipated or until its flow is intercepted by the rupture at A. The 

 charge retained by the condenser is then measured by discharging 

 it through a D'Arsonval galvanometer (not indicated on the diagram) 

 which has been calibrated for ballistic use. 



This series of operations is successively repeated for many values 

 of the time interval. 



It is thus possible to determine the charge of the condenser at any 

 moment after the rupture of the battery branch. Some of the results 

 obtained are shown in fig. 1 and fig. 2. The ordinates represent the 

 charges in arbitrary units ; the abscissas give the time in thousandths 

 of a second. 



The data for the curves are as follows : 



Value of r Inductance Capacity 



in ohms. in henries. in farads. 



f Curve A.... 10,000 0'42 5 x lO" 6 



Fig. 1<^ Curve B. . . . 3,100 



L Curve C.... 552 



Fig. 2 ............ 



Fig. 1, Curve A represents a merely leaking discharge; 



Curve B represents the critical discharge that just fails to 



ever charge the condenser negatively ; 

 Curve C represents the critical discharge that just fails to 



be oscillatory ; 

 And the curve in fig. 2 represents a typical oscillatory discharge. 



To find from theory what these curves should be, we must solve 

 the equation 



where p is the dissipation constant, and Q is the charge at any 

 insiant. The constants of integration must be determined to suit the 

 conditions that 



dt 



The solution has one of two forms according as 



, > 4L 



*< tr; 



