__________________________________. 21 April 1820: Hans Christian Oersted (1777-1851) discovered that the needle of a compass turned when a wire carrying current was near, and the turn was at right angles to the wire. He showed there was a link between electricity and magnetism.
Before this, Oersted had travelled to Germany and France, 1801-1803. In Germany, he met Johann Wilhelm Ritter in Jena. Ritter had already concluded that electricity and magnetism were related, so Oersted’s 1920 discovery may not have really been the unexpected ‘surprise’ which Oersted claimed. He announced his discoveries on 21 July 1820 in a paper written in Latin. However, the experiment was shown well before that (21 April 1820) to a large class of his students, at which he claimed the unexpected surprise at observing this during presentation to the class. It seems sure that he actually knew this would happen before 21 July 1820 and the ‘surprise’ was announced for impact and other reasons.
By September 1820, Francois Arago was showing this in France. and it is claimed that Ampère attended this lecture by Arago.
The 1820 COPLEY medal of the British Royal Society was awarded to Oersted.
Oersted was a follower of Kant’s philosophy, and did not believe in atoms – he believed that matter could be divided endlessly to infinitely smaller pieces. It also has to be remembered that at this time, many scientists believed in what is now called Astrology (which was mixed into the true science of Astronomy), and they believed that the timing of important scientific discoveries should be related to the timing of cosmological events outside the control of humans. A specific and relevant example is the following: In a letter to Oersted of 22 May 1803, Ritter prophesied a remarkable discovery in 1819 or 1820. He meant that the years of maximum inclination of the ecliptic (1745,1764,1782,1801) coincided with outstanding discoveries in the field of electricity …….1745 Invention of the Leiden jar by Kleist; 1764 Invention of the electrophorous by Wilcke ; 1782 Invention of the condenser by Volta 1801 Invention of the Voltaic pile. … Ritter went on: 'You will not have to reckon with a new epoch or its start any earlier than the year 1819 or 1820. This we might well witness….. behold Oersted discovered in 1820 the effect of the electric current upon the magnet! It might be concluded on this basis that Oersted might have deliberately ‘delayed’ his discovery to 1820, to comply with this advice of Johann Wilhelm Ritter.
There are claims that these discoveries were preceded by the Italian Gian Domenico Romagnosi, who said he had seen the deflection of a magnetic needle when it was near to a battery. However it is now considered likely that because he had no complete closed circuit to carry current; this deflection may have been caused by electrostatic charge.
Ándre-Marie Ampère (1775-1836) made the discovery that a wire carrying electric current can attract or repel another wire carrying current and this led him to the Law of Electromagnetism. Ampère had been encouraged to learn anything and everything by his father, but was left to make his own way through available books, etc. in his father’s library. It is said that he started his studies of mathematics at the age of 13. Clearly he became extremely knowledgeable. In 1804, Ampère had moved from Lyon to Paris, and he taught at the École Polytechnique and became professor of mathematics despite a lack of the usual formal qualifications. He was considered an outstanding teacher.
It is sure that by September 1820 he had heard of Oersted’s work with the implication that this led him to investigate why electric current produced magnetism. At this time he discovered that magnetism without magnets was possible, and that led to the idea and use of a solenoid to get more magnetism from a given amount of electric current.
In a very thorough description published in 1823 (Theorie des phenomenes electro-dynamique’, Memoires de l’Institut, Volume IV, Ampère describes in extreme and mathematical detail his explanations and conclusions. This seems to have been re-published perhaps with corrections in Volume V1, dated 1827. This 217 page report can be found on line as a pdf file at: http://www.ffn.ub.es/luisnavarro/nuevo_maletin/Ampere_1823_Electrodynamique.pdf
The various reports about all these events need to be looked at carefully, because of discrepancies of the reported dates of various claimed events. Illustrations are from English translation of Ganot’s Cours Elementaire de physique, by R.Atkinson, London, 1878 (3rd Edition) - to follow .......