126 MAGNETS AND ELECTRICITY 



magnet. If each half is broken in two, we have four 

 magnets, each with a north-seeking and a south-seeking 

 end, or pole. Finally, if we lay the four pieces down end 

 to end, so that the north-seeking end of one piece touches 

 the south-seeking end of the next piece, all the four pieces 

 together will again form one magnet, which will attract 

 iron filings only at the two ends. 

 The law of magnets is: 



Like poles repel each other; opposite poles attract. 



If we bring the north-seeking end of a bar magnet near 

 the south-seeking pole of a suspended magnet, they will 

 attract each other; but if the two north- 

 seeking ends are brought together, 

 there will be repulsion between them 

 (Fig. 112). 



Fia. 112. 



137. Magnetic Substances. A mag- 



net of steel retains its magnetism for a 

 long while; hence it is called a permanent magnet. It 

 will, however, lose its magnetism if __ ^ s 

 heated. 



If one pole of a magnet is held near a 

 piece of soft iron, such as a nail, the nail Fia 113 . 



itself becomes a magnet (Fig. 113), and A n n f- n h d el d f 

 attracts iron filings or another nail. But ^f becomes a mag ' 

 when the nail is removed from the mag- 

 net, its magnetic properties disappear. Thus, while steel 

 can be permanently magnetized, soft iron forms only a 

 temporary magnet. 



