MAGNETS AND MOTORS 



391 



Law of Magnetic Attraction. The point of the compass needle 

 which is attracted toward the North magnetic pole is called the plus 

 or North end, and the opposite end the minus or South end. 



FIG. 271. S attracts N: N repels N. 

 What will S and S do? 



Current enuring 

 this coll produces 

 majnec which 

 is attracted toward 

 ^4- electro 



FIG. 270. No matter how many 

 times a magnet is broken, each 

 part becomes a magnet with N 

 and $ poles. 



Experiment. Bring the North end 

 of a magnetic bar near the North end 

 of the compass needle. Bring the 

 South end of the bar near the North 

 end of the compass needle. Explain 

 what happens. What does the law 

 " Like poles of magnets repel each 

 other, and unlike poles attract each 

 other," mean? 



Motor. The attraction and 

 repulsion of magnets is made use 

 of in the electric motor. The 

 electric motor consists of a num- 

 ber of electro-magnets fastened 

 rigidly to a frame, and other 

 magnets fastened to an axis, 

 called an armature, on which 

 there is a drum for brushes to 

 allow the current to enter the 



motor. In Fig. 272 the electro-magnet A (+) is attracted 

 minus ( ) magnet B and repelled by the plus (+) magnet 

 the magnet D is attracted by the magnet C and repelled 



Armature 



15 attra-cted toward 

 th electro 



FIG. 272. The Motor. 



by the 

 C; and 

 by the 



