CHAPTER XXXII 



MODERN ELECTRICAL INVENTIONS 



296. An Electric Current acts like a Magnet. In order to 

 understand the action of the electric bell, we must consider a 

 third effect which an electric current can cause. Connect 

 some cells as shown in Figure 200 and close the circuit 



through a stout heavy copper wire, 

 dipping a portion of the wire into 

 fine iron filings. A thick cluster 

 of filings will adhere to the wire 

 (Fig. 210), and will continue to 



as t ^ e curren t 



FIG. 210. -A wire carrying current c \[ n g to ft SQ 

 attracts iron filings. 



flows. It the current is broken, the 



filings fall from the wire, and only so long as the current flows 

 through the wire does the wire have power to attract iron 

 filings. An electric current transforms a wire into a magnet, 

 giving it the power to attract iron filings. 



Although such a straight current bearing wire attracts iron 

 filings, its power of attraction is very small; but its magnetic 

 strength can be in- 

 creased by coiling as 

 in Figure 211. Such 



_ FlG. 211. A loosely wound coil of wire. 



an arrangement of wire 



is known as a helix or solenoid, and is capable of lifting or 

 pulling larger and more numerous filings and even good- 

 sized pieces of iron, such as tacks. Filings do not adhere 

 to the sides of the helix, but they cling in clusters to the ends 



