PRELIMINARY TECHNIQUE. 11 



currents are continuously induced in the secondary coil due to the 

 constant interruption of the current in the primary by the vibrating 

 spring. The latter effect is called a tetanizing current. 



It has been found that the least induced current is produced 

 when the secondary is at right angles to the primary; from this 

 position the current is increased more and more as the secondary 

 becomes more nearly parallel. In addition to the angular relation- 

 ship, the distance between the two coils determines the strength 

 of current induced, the closer they are the greater the effect. 



FIG. 1. Inductorium: (a) Primary Coil; (b) Secondary Coil; (c) Bar 

 for short-circuiting the secondary terminals. Connect the source of 

 supply to 1 and 2 for single shocks and to 1 and 3 for a succession of rapid 

 shocks. 



Experiment 1. Try the following. -1. Connect the electrodes to 

 two terminals on the table so as to obtain 2 volts. Touch the 

 tongue with the electrodes and then make and break the circuit 

 by means of the switch. Repeat with increasing voltage. 

 Describe the effects at make, at break and during the passage 

 of the current. 



2. Connect the binding posts 1 and 2 (Fig. 1) of the primary 

 coil to 4 volts on the table, with a simple key in the circuit. 

 Connect the electrodes to the end of the rods upon which the 

 secondary slides. With the secondary coil far out and parallel 



