320 



MODERN ELECTRICAL INVENTIONS 



current flows back to the battery. As soon as the current 

 flows, the coils become magnetic and attract the soft iron arma- 

 ture, drawing it forward and causing the 

 clapper to strike the bell. In this position, 

 vS no longer touches the screw /*, and 

 hence there is no complete path for the 

 electricity, and the current ceases. But 

 the attractive, magnetic power of the 

 coils stops as soon as the current ceases; 

 hence there is nothing to hold the arma- 

 ture down, and it flies back to its former 

 position. 



FIG. 214. A horse- T j 



shoe electromagnet is in & 



powerful enough to this,tlOW- 

 support heavy weights. 



ever, the 



armature makes contact at 

 P through the spring, and 

 the current flows once more; 

 as a result the coils again 

 become magnets, the ar- 

 mature is again drawn for- 

 ward, and the clapper again 

 strikes the bell. But imme- 

 diately afterwards the ar- 

 mature springs backward 

 and makes contact at P 

 and the entire operation is 

 repeated. So long as we 

 press the button this process 

 continues producing what 

 sounds like a continuous 



FIG. 215. The electric bell. 



jingle ; in reality the clapper strikes the bell every time a 

 current passes through the electromagnet. 



