The New Student's Reference Work/Ampère, Andre-Marie

The New Student's Reference Work  (1914) 
Ampère, Andre-Marie

Ampère (än-pêr′), Andre-Marie (born 1775, died 1836).  A distinguished French physicist and mathematician.  Most of his working life was spent at the École Polytechnique, the great military school of Paris.

Ampère’s most important contributions to knowledge are, perhaps, the three following:

First:  His clear analysis and mathematical description of the work of Oersted.  It was in the autumn of 1820 that Oersted discovered the effect of an electric current upon a magnetic needle.  In less than one week after learning of this discovery, Ampère had extended the results by experiment and had reduced the description to a mathematical formula.

Second:  The discovery that electric currents produce a magnetic effect upon each other: so that when the currents in two wires are flowing in parallel directions, they attract each other; but, when flowing in opposite directions, repel each other.

Third: Ampère introduced the very fruitful hypothesis that magnetic substances are made up of molecules in which electric currents circulate but meet no resistance.  These currents are therefore permanent.

According to this view, a body is magnetized when its molecules are made to face more or less one way.