210 OUR PHYSICAL WORLD 



pointing in one direction after the current ceases and the bar is 

 therefore a more or less permanent magnet. 



Michael Faraday, of the Royal Institute in London, heard of 

 Ampere's work, and thought that if a magnet can be made by 

 passing a current of electricity through wire wound around an 

 iron bar, the reverse of this also might be true, namely, that if 

 a magnet were put into a coil of wire it would make an electric 

 current flow in the wire. So he made a hollow coil of many 

 turns of insulated wire, and connected the ends of the wire with a 

 galvanoscope. Then he introduced one end of a strong bar 

 magnet into the center of the coil, and saw that the magnetic 

 needle did actually show a current. He found, however, that 

 when the magnet was lying quietly in the coil no current was 

 produced. It was only when the magnet was moving into or 

 out of the coil that the current was manifest, and it flowed in one 

 direction when the magnet was moving into the coil and in the 

 opposite direction when it was moving out. 



