LABORATORY MANUAL OF PHYSIOLOGY. 



may be short-circuited anywhere along its length by means of a 

 sliding metal rider. 



5. Induced Currents. If a conductor through which a current 

 is flowing is brought near to another and parallel conductor, an in- 

 stantaneous current is in- 

 duced in the latter and op- 

 posite in direction to that of 

 the former. When the first 

 conductor is again removed 

 from the vicinity of the second, 

 a current is again induced in 

 the second, but now in the 

 same direction as that in the 

 first. The same effect is pro- 

 duced by making and break- 

 ing the circuit in the first wire 

 or by alternately bringing a 

 conductor into and away from 

 the vicinity of a magnet. 



The Inductorium, used in 

 the physiological laboratory, 

 is based on these principles 

 (see Fig. 6). It consists of 

 a primary coil of heavier 

 wire of few windings (P), surrounding a movable core of 

 iron wire, a secondary coil (S) of finer wire and many more wind- 

 ings, not connected with the primary coil, and an automatic inter- 

 rupter which may or may not be placed in circuit with the primary 

 coil. 



II. PRACTICUH. 



Take two hollow spools, one considerably larger than the other, 

 winding the small one with heavy insulated copper wire and the 

 large one with fine insulated copper wire. The sma 1 ! coil is the 

 primary and is to be connected with the battery. The large coil is 

 the secondary and is to be connected with the galvanometer. 



[16] 



FIG. 6. Diagrammatic Drawing of In- 

 ductorium. P, Primary coil ; S, second- 

 ary coil ; C, core ; B, battery ; Af, magnet 

 of interrupter ; A, armature of interrupter ; 

 S#, spring of interrupter. 



