Oersted, Hans Christian (1777–1851)

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OERSTED, HANS CHRISTIAN (1777–1851)

Hans Christian Oersted, the son of an impoverished pharmacist, made the great discovery that electricity and magnetism are related. Oersted was born on the small Danish island of Langeland, about halfway between Copenhagen and Hamburg. There was no school in Langeland, so he and his younger brother, Anders Sandoe, went to the homes of neighbors who taught the boys to read and write. Later the town surveyor taught them mathematics, and the mayor taught them English and French. When he was twelve, Hans began to help his father in the pharmacy, and the work stimulated his interest in science.

In 1794 Oersted and his brother Anders matriculated at the University of Copenhagen. Hans studied the sciences, and Anders, who eventually became a leading jurist and a minister of state, studied law. The brothers were recipients of a small state scholarship, but largely supported themselves at the university by tutoring. They lived together, shared costs, and devoted themselves wholeheartedly to their studies. In 1797 Hans Christian Oersted was awarded a degree in pharmacy and, in 1799, received a Doctor of Philosophy degree.

After graduation, Oersted secured a position as a part-time lecturer at the university; he also managed a Copenhagen pharmacy. Word of Alessandro Volta's discovery of a way of producing a continuous electric current reached Copenhagen in 1800, and Oersted began experimenting with acids and alkalis using a voltaic pile. The following year, he left Copenhagen and visited a number of famous scientists during the traditional year of travel taken by European students following graduation. If all the scientists he met, Oersted was most influenced by Johann Wilhelm Ritter, an eccentric German physicist whom he visited for several weeks in Jena. Ritter had also begun his career as a pharmacist and had already discovered ultraviolet light, thermoelectric currents, and the process of electroplating. Oersted returned to Copenhagen in 1803 and applied to the university for a position as professor of physics, then called "natural philosophy," but was refused. He continued lecturing at the university in the schools of medicine and pharmaceuticals, and at the same time managed the pharmacy, carried on electrochemical experiments, and published his results. In 1806 he was finally made a professor of physics at the University, although he not become a full professor until 1817.

From 1803 to 1820, Oersted's life centered around the cultural and academic life of what was then the small city of Copenhagen. He took part in political and academic debates, participated in a royal geological expedition in Denmark, and became a popular public lecturer. He was knighted and achieved the position of secretary of the Royal Society of Copenhagen. In 1813 he again visited Germany and France and published a book about electrochemical forces. In it Oersted commented on magnetic forces and clearly stated that the connection between electricity and magnetism should be investigated. Before the publication of Oersted's book, it had indeed been suspected by many scientists that magnetism and electricity were somehow related. It was known that iron rods were magnetized by the action of the electric currents passing through them as the result of lightning strikes. However, no scientific verification or understanding of the relation existed.

Oersted's discovery of the relation between magnetism and electricity in 1820 is often described as the result of a lucky accident occurring during the course of a laboratory demonstration. However, Oersted declared that he had actually prepared the experiment before the demonstration and only carried it out during the demonstration to some advanced students because that was the first opportunity. What Oersted observed was that a wire carrying an electric current caused a nearby magnetic compass needle to assume a position perpendicular to the wire, and if the current were reversed, the needle would reverse position.

After this initial discovery, Oersted waited three months, apparently for the construction of a more powerful current source. He then carried out sixty experiments to show that the magnetic field due to the current in a wire is circular around the wire. He showed that the effect is independent of the type of wire, and that it is independent of any intervening common materials. Later, he proved that the effect is proportional to the current in the wire.

On July 21, 1820, Oersted published a four-page Latin monograph, "Experiments on the Effect of a Current of Electricity on the Magnetic Needle." He distributed the monograph to leading scientists throughout Europe and, in the following months, the monograph was reprinted in translation in the most important scientific journals throughout Europe and Britain. A whole new field of investigation and technology was opened. Within a year the laws of electro-dynamics were formulated, the electromagnet was invented, and the first primitive electric motor was demonstrated. The first electric telegraph and the first primitive electric generator would soon follow.

Oersted was named a fellow of several learned societies, presented with medals, and awarded cash prizes. At home, Oersted became Denmark's leading citizen. He continued his research, but as an international figure he traveled extensively, became fluent in many languages, and met with the leading scientists of the time. He gave frequent public lectures and became a director of the Royal Polytechnic Institute of Copenhagen. He also had a lifelong interest in literature and, in 1829, he founded a literary journal to which he frequently contributed articles about science. In 1850, the fiftieth anniversary of his appointment at the university was celebrated as a national holiday, and he was given a country home by the government. When he died in 1851, more than 200,000 people joined the funeral procession.

Oersted had a kindly and sympathetic personality. He had a successful marriage and a large family. In 1819 he befriended a poor fourteen-year-old boy who over the years became virtually another member of the Oersted family. The boy, Hans Christian Andersen, was to become the great Danish storyteller. Andersen often referred to himself as "little Hans Christian" and to Oersted as "great Hans Christian."

Leonard S. Taylor

See also: Electricity; Electricity, History of; Electric Motor Systems; Electric Power, Generation of; Magnetism and Magnets.