CHAP, in.] ELECTRICITY AND MAGNETISM. 



steel bars, had failed. 1 The true connection between 

 magnetism and electricity remained to be discovered. 



In 1819, Oerstedt, of Copenhagen, showed that a 

 magnet tends to set itself at right-angles to a wire carry- 

 ing an electric current. He also found that the way in 

 which the needle turns, whether to the right or the left 

 of its usual position, depends upon the position of the 

 wire that carries the current whether it is above or 

 below the needle, and on the direction in which the 

 current flows through the wire. 



185. Oerstedt's Experiment. Very simple appar- 

 atus suffices to repeat the fundamental experiment. Let 

 a magnetic needle be suspended on a pointed pivot, as 

 in Fig. 78. Above it, and parallel to it, is held a stout 



Fig. 78. 



copper wire, one end of which is joined to one pole of a 

 battery of one or two cells. The other end of the wire 

 is then brought into contact with the other pole of the 

 battery. As soon as the circuit is completed the current 

 flows through the wire and the needle turns briskly aside. 

 If the current be flowing along the wire above the needle 



1 Down to this point in these lessons there has been no connection between 

 magnetism and electricity, though something has been said about each. The 

 student who cannot remember whether a charge of electricity does or does 

 not affect a magnet, should turn back to what was said in Art. 91. 



