332 



MAGNETS AND CURRENTS 



FIG. 226. A helix through which current 

 flows always points north and south, if it 

 is free to rotate. 



sent through it, the helix will immediately turn and face 



about until it points north and south. If it is disturbed from 



this position, it will slowly swing back until it occupies its 



characteristic north and south 

 position. The end to which 

 the string is attached will per- 

 sistently point either north or 

 south. If the current is sent 

 through the coil in the opposite 

 direction, the two poles ex- 

 change positions and the helix 

 turns until the new north pole 

 points north. 



c. If a coil conducting a 

 current is held near a sus- 

 pended magnet, one end of 



the helix will be found to attract the north pole of the magnet, 



while the opposite end will be found to repel the north pole of 



the magnet. In fact, the helix will be found to behave in every 



way as a magnet, with a 



north pole at one end and a 



south pole at the other. If 



the current is sent through 



the helix in the opposite di- 



rection, the north and south 



poles exchange places. 

 If the number of turns 



in the helix is reduced until 



hut a sinp-le loon remains 

 m ^ ie ns > 



the result is the same; the 

 single loop acts like a flat magnet, one side of the loop always 

 facing northward and one southward, and one face attracting 

 the north pole of the suspended magnet and one repelling it. 



FIG. 227. - A wire through which current flows 

 i s surrounded by a field of magnetic force. 



