CII. XXXVI. 



AMPERE'S EXPERIMENTS, 



37i 



facts about electro-magnetism. He found that it was quite 

 true, as Oersted had said, that the magnet always lies across 

 the electric current ; but he showed that the north pole of 

 the magnet turns different ways, according to the direction 

 in which the current flows. Thus, if the current 1 flows 

 from south to north above the magnet, in the direction a b, 

 Fig. 64, then the north pole of the magnet turns towards 

 the west ; but if it runs from north to south above the 

 magnet, in the direction a b, Fig. 65, then the north pole 

 turns towards the east. Again, if it runs from north to south 

 below the magnet, in the direction c d, Fig. 64, the magnet 



FIG. 64. FIG. 65. 



Diagrams showing the direction of a Magnet acted upon by Electric Currents. 

 a b c d, Direction of current. 



will again turn to the west ; while lastly, if it runs from 

 south to north below the magnet, c d, Fig. 65, the north pole 

 turns again to the east. In order to remember these differ- 

 ent directions easily, Ampere gave something like the follow- 

 ing rule. If a man will imagine himself to be standing so 

 that the positive current would come out of his mouth and 

 return by his feet, the north pole of the magnet will always 

 be on his left-hand side. 



1 To avoid confusion, the current from the positive pole of the 

 battery is always spoken of as the current. 

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