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PROCEEDINGS OF THE AMERICAN ACADEMY. 



OX shows its final value. The second current is represented by the 

 curve ADWU plotted under AN and displaced to the right so that the 

 sudden increase in the absolute strength at the time of the change in 

 J/ may appear. The flax of magnetic induction through the primary 

 circuit is represented on the usual scale by the shaded area. The 



TIME. 



Figure 21. At the time OA, the self -inductance of the primary circuit of 

 a certain induction coil without iron is suddenly doubled, while the self- 

 inductance of the secondary circuit and the mutual inductance of the two 

 remain unchanged. OGCJK shows the course of the primary current and 

 TDPSL that of the secondary current. 



black area points to a decrease in this flux which goes on from the time 

 XF to the time XGr, when the current falls below its final value. The 

 induction flux linked with each of the two circuits is plotted against 

 the time in Figure 24. These quantities are shown to be continuous 

 at the time of change in the inductance, as, of course, they should be. 



Figure 25 shows another arrangement of two neighboring circuits and 

 an analogous mechanical system. The gap is closed at first, but is 

 suddenly opened when the current has become steady. The mass W 

 moves alone under the action of a force E which urges it in the direc- 

 tion of the bottom of the page, and the air resistance. The motion 



