Hans Christian Orsted, one of the leading scientists of the nineteenth century, played a crucial role in understanding electromagnetism. In 1820 he discovered that a compass needle deflects from magnetic north when an electric current is switched on or off in a nearby wire.
This showed that electricity and magnetism were related phenomena, a finding that laid the foundation for the theory of electromagnetism and for the research that later created such technologies as radio, television and fiber optics. The unit of magnetic field strength was named the Oersted in his honor.
Hans C. Orsted in his childhood
Hans Christian Orsted was the son of Soren Christian Orsted and Karen Hermandsen. His father was a pharmacist of Rudkobing on the island of Langeland. Hans with his brother, Anders Sandoe Orsted (1778-1860), later professor of jurisprudence and politician, received privately and by self-study an education which enabled them to travel in 1793 to Copenhagen and there, the next year, pass the university entrance examination, to which they had submitted themselves.
Orsted’s farmacy in Rudkobing,
Both brothers early showed signs of exceptional gifts and set themselves great aims for their future. H.C. Orsted’s interest in science was early aroused by working in his father’s pharmacy, and so it was natural that he should train for pharmacy, as there were no possibilities of studying physics and chemistry at Copenhagen University then; it was he who afterwards provided them.
As early as 1797, he passed the pharmaceutical examination with distinction, and already in 1796 and 1797 succeeded in doing the prize papers (about treatise on amniotic fluid) in both aesthetics and medicine, in each case winning the prize. Two years later he was awarded a doctorate for a dissertation on Kant’s philosophy.
After 1800 he studied the new galvanism. In the summer of 1801 he was awarded a travel scholarship, which together with a public grant enabled him to spend three years abroad, visiting both Germany and France. On these travels he came into close contact with the German physicist Ritter, who strongly influenced him.
He was also fascinated both by J.J. Winterl’s remarkable chemical philosophy and by Fichte’s ideas on universal reason and the unity of natural forces. On the other hand he was put off by French mathematical physics. It was in the early days of the philosophy of nature and romanticism, and under Ritter’s influence Orsted undeniably adopted a somewhat uncritical approach to the new currents, which in a book he published – to some extent, though only for a time, damaged his standing among his colleagues.
Later, however, he disengaged himself from this uncritically accepted influence, and it is reasonable to emphasize that if romanticism and its relationship to the philosophy of nature meant a very powerful inspiration to Orsted it would be wrong to regard him as solely a child of romanticism. He was also to a considerable extent rooted in the period before, in the philosophy of Kant, and particularly in the belief of the Enlightenment in the value and possibility of human advancement through rational education. His youthful adoption of Immanuel Kant’s philosophy endured, although he modified Kant’s ideas by belief in a fundamental unity of the forces of nature. True, he felt attracted by Schelling’s philosophy of nature with its quest for unity, but in time he became more and more critical of purely speculative philosophy, reproaching it for failing to base itself on reality.
Returning home, in 1806, Orsted became a professor at the University of Copenhagen, where his first physical researches dealt with electric currents and acoustics. He was the actual founder of physical studies at Copenhagen University. Considerable university activity was developed from his work, leading finally to thorough and systematic teaching of physics and chemistry, together with the establishment of relatively good laboratory conditions.
In the years 1812 and 1813 Orsted went on his second major foreign journey to Germany, Belgium and France. Although still under the influence of the speculative philosophy of nature, he admitted that he had meanwhile moved away from its views and that it was not possible for him to achieve a profitable exchange of ideas between himself and Fichte and Schleiermacher.
Back home, he married Birgitte Ballum, with whom he lived a harmonious and very happy married life, having five daughters and three sons.
From 1815 to his death he was Secretary to the Royal Danish Academy of Sciences and Letters.
During an evening lecture in April 1820, Orsted discovered experimental evidence of the relationship between electricity and magnetism. While he was preparing an experiment for one of his classes, he discovered something that surprised him. In Oersted’s time, scientists had tried to find some link between electricity and magnets, but had failed.
It was believed that electricity and magnetism were not related. As Oersted was setting up his materials, he brought a compass close to a live electrical wire and the needle on the compass jumped and pointed to the wire. Oersted was surprised so he repeated the experiemnt several times. Each time the needle jumped toward the wire. This phenomenon had been first discovered by the Italian jurist Gian Domenico Romagnosi in 1802, but his announcement was ignored.
Hans Christian Orsted was demonstrating the heating effects of the Voltaic Pile when he noticed that the needle of a compass sitting next to it spun off of north. This occurred every time the Voltaic Pile was in use. This eventually lead him to the conclusion that an electric current creates a magnetic field and electromagnetism was born.
He himself told the story of how, one day in April when he was pondering on a lecture about electricity and magnetism in which he would employ a new electric battery, it occurred to him that just as light and heat radiate from all sides of a live wire, so, conceivably, magnetic action might similarly be emitted from the wire. He resolved to investigate this by inserting a platinum filament in the wire between the battery terminals and causing them to glow by means of the current, meanwhile holding it over a small compass needle in the line of it.
There was no time for testing the theory before the lecture; but during it he became so convinced of the idea’s correctness that he at once carried out the experiment, and found that the needle was deflected, that it was deflected in the opposite direction when the current was reversed, and that it was without effect when the needle was held at right angles to the wire.
As the effect was only slight, since so was the current, he put off further research for three months in order to have plenty of time for investigating the phenomenon. Then, in July, he commenced a very extensive study, resulting in a paper (in Latin!) that was quickly translated into the major languages in leading scientific journals.
His discovery of the magnetic effect of electrical currents in 1820 was immediately recognised as an epoch-making advance, although he left further work on electromagnetism to others. Andre-Marie Ampere quickly repeated Oersted’s experiment, and formulated them mathematically. Orsted also discovered that not only is a magnetic needle deflected by the electric current, but that the live electric wire is also deflected in a magnetic field, thus laying the foundation for the construction of the electric motor.
In addition to electromagnetism he worked on the compressibility of gases and liquids and on diamagnetism. Orsted’s discovery (1820) of piperine, one of the pungent components of pepper, was an important contribution to chemistry, as was his preparation of metallic aluminum in 1825.
In 1822-23, Orsted went on his third major journey abroad, to Germany, England and France, with royal support and money for buying instruments.
He appreciated the need to spread knowledge of scientific advance, and in 1824 created the still extremely active “Society for the Dissemination of Natural Science” – a society devoted to the spread of scientific knowledge among the general public. Since 1908 this society has awarded an Orsted Medal for outstanding contributions by Danish physical scientists. It was on his initiative in 1829 that the Polytechnical Institute in Copenhagen, now the Technical University of Denmark, was established, where engineering received a scientific foundation. He became the first director of this Institute.
Hans Christian Orsted is one of the most luminous figures in the intellectual life of Denmark. He had lasting influence on many aspects of Danish culture and society. Thus he was one of the first to appreciate and encourage Hans Christian Andersen when this great Danish writer found the fairy tale as his proper genre. By nature he was a kind and exceedingly helpful man, who was a great inspiration to his associates; but although his dealings were always marked by a high degree of consideration he could in crucial situations display great firmness and resolution, never hesitating to advance radical views and opinions. He is one of those figures in Danish history who appear in so noble a cast that the picture of him and his work comes to seem almost too undifferentiated.
Apart from these accomplishments, Orsted wrote poetry and prose. Shortly before his death, he published a series of collected articles under the title “The Soul in Nature”, a masterpiece expressing the essence of his philosophy of life. Finally, there remains to be mentioned Orsted’s great interest in the Danish language, to which he contributed a number of innovations, such as the words “brint” and “ilt”, for hydrogen and oxygen.
Oersted (Oe) is the CGS unit of magnetic field strength. The oersted is defined to be the field strength in a vacuum at a distance 1 centimeter from a unit magnetic pole. A field of one oersted generates a magnetomotive force of 1 gilbert per centimeter of conductor. There is no named MKS unit of field intensity, but the oersted is equivalent in MKS units to 79.577 472 ampere-turns per meter. Before 1930 this unit was called the gauss.