83 



On closing the P circuit this spring oscillates automat- 

 ically opening and closing the P circuit, and a succession of 

 induction currents is generated in the S coil. The rate of 

 their occurrence depends upon the length of the spring. 



Explanation : The current from the battery flows through 

 the binding screw d, up the pillar- through the spring, up 

 through the top contact screw e to the P coil, and thence 

 round the electro-magnet / and back by the base of c to the 

 battery. Fig. 11. 



When the current flows round the circuit, /is magnetized 

 and draws down the spring thus breaking the top contact. 

 Upon this the current stops flowing, the magnet ceases to 

 act, the spring is released and again makes contact with e and 

 so the circuit is re-established and the cycle begins anew. 



As the break shock is always the stronger of the two, it 

 follows that if these shocks are passed through a tissue for 

 some time that polarization effects will be set up. Ordinarily 

 they are employed for a short time only, and this effect can 

 be disregarded. 



314. Electrolysis of Potassium Iodide. An interest- 

 ing example of electrolysis is seen in the decomposition of 

 potassium iodide. Dip a small piece of filter paper in starch 

 paste to which about 5% of potassium iodide has been added 

 and lay Ihe paper over the electrodes. Make and break the 

 circuit using the single induced current. Iodine is set free at 

 the anode and turns the starch blue, forming the iodide of 

 starch. This method may be used to determine which is the 

 anode. The direction of the current in the secondary coil of 

 the inductorium may thus be recognized. (Porter.) 



fjHuicle 



r*S 



Jfemt. 



•*^ 

 % 



V 

 ^ 



Fig. 18 



