Hans Christian Ørsted (1777-1851) was for most of his life deeply immersed in the philosophy of Immanuel Kant, whose major work, The Critique of Pure Reason, published when young Hans was four years old. The heavy volume was much discussed by European thinkers and in later years it heavily influenced Ørsted’s view of reality. A central tenet of Kantian thought was that there is unity in nature and strong relationships among natural phenomena.
Increasingly over the years, Ørsted was motivated to study physics. At the University of Copenhagen where he became a professor in 1806, he investigated electric currents. Allesandro Volta’s invention of the galvanic battery a few years earlier provided experimenters including Ørsted with the physical hardware for some serious experimentation. This was the background for an unanticipated discovery of great consequence.
During a lecture he gave in 1820, by chance Ørsted noticed that a compass needle was deflected from its usual north-south alignment when current, supplied by a voltaic pile, happened to be flowing through a nearby conductor. This provided positive proof of the close relationship between electricity and magnetism. Ørsted’s Kantian perspective was verified at this historic moment. Properly aligned and manually pulsed, the compass needle could be made to turn in one direction continuously, in essence becoming an externally commutated dc motor.
The fact that the discovery was accidental does not diminish the stature of this original thinker and researcher. He was energetic and well organized and his work continued unabated in the years that followed.
In 1825, Ørsted became the first person to isolate elemental aluminum by means of a reduction of aluminum chloride.
Much of his work was administrative and organizational, always with a view of creating educational venues through which a new generation of electrical engineers were inspired to discover fundamental parameters that we use in our work on a daily basis.
To honor him, the CGS system of units uses the Ørsted, abbreviated Oe, as the unit of the auxiliary magnetic field H, just as gauss is the unit of measurement for the B field. (In the SI system, amperes-per-meter is used for the H field and tesla is used for the B field.)
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