MAGNETIC ATTE ACTION AND REPULSION. 707 



not neutralised. The ultimate external action may 

 therefore be represented as at B in fig. 357, or, since all 

 these small active portions of these currents are at 

 infinitely small distances from each other, as at (7, which 

 represents them as a single current. The active current 

 is therefore also in the succeeding figures legitimately 

 represented as a single one which traverses the outside 

 of a magnet. 



When the current is transmitted through two electro- 

 magnets, one of which is suspended and can freely 

 move, while the other is held in the hand, powerful 

 attraction or repulsion takes place when one pole of 

 the latter is brought near to either pole of the sus- 

 pended magnet. If the direction of the current in both 

 magnets be observed, and their poles be determined 

 in accordance with the above rule, it will be found that 

 the north pole of one magnet attracts the south pole of 

 the other magnet, but that north pole repels north pole, 

 and south pole repels south pole. Poles of the same name 

 repel, and poles- of contrary name attract one another. 



These phenomena are an immediate consequence of 

 the previous laws. In fig. 358 A let two electro- 

 magnets be represented by a and &, and the direction 

 of the current by the arrows. These directions are 

 the same in both magnets, hence attraction takes place, 

 and applying the above rule which determines the name 

 of the pole from the direction of the current r s 1 and s> 2 

 are seen to be south poles, n^ and n. 2 north poles, and 

 the two ends turned towards each other, that is, the 

 south pole Si and the north pole n^ attract each other. 

 When a and b are in the position B of fig. 358, the 

 current in one flows in an opposite direction to that 



z z 2 



