Tribute to Hans Christian Oersted, 200 Years after His Experiment – Part I

Hans Christian Oersted

This year, a bicentennial passed by, probably without the celebration and commemoration it deserved. A search of ‘Oersted’s experiment 200th anniversary’ throws up barely half a dozen pages, most of them based in Oersted’s native Denmark. Almost all physics textbooks mention his experiment in the introduction to electromagnetism, but I wonder if in most people’s minds it is just that – simply a prelude to all the other great discoveries made by Michael Faraday and others.

In the prevailing confusion at the height of the lockdown, I myself missed the date – 21 April – when, during a lecture-demonstration, Oersted first noticed a magnetic needle move when a current was switched on.

As my little tribute to the monumental discovery, in this post I look more closely at the details of the story. Was it just an accidental discovery as most modern textbooks narrate it? Or was Oersted expecting to find a link between electricity and magnetism? I dive into an excellent article written by science historian and educator Nahum Kipnis to find out.

As early as 1812, Oersted had written about his belief in the unity of the forces of nature – heat, light, chemical affinity, electricity and magnetism. This was a purely metaphysical speculation arising from his worldview of nature as having order and symmetry. It did not make Oersted formulate any testable hypothesis or design any experiment for the next eight years.

His interest in this topic was revived by a course he had to teach at the University of Copenhagen in 1819-20. In April, he was scheduled to deliver a lecture on new discoveries in physics and chemistry to a group of advanced students. Oersted planned to discuss various connections between electricity, magnetism and galvanism (the group of phenomena related to the electrochemical battery discovered by Volta).

This was not an entirely new area of research, for attempts to find links between static electricity and magnetism, and between magnetism and chemistry, had been going on since the mid 1750s. Some scientists had succeeded in weakly magnetising a steel needle by passing a discharge from a Leyden jar (a primitive capacitor made from a glass jar) through the needle.

There is considerable debate among science historians about what actually happened in that legendary lecture. To make things murkier, the supposed eye-witness account of Christopher Hansteen, a student of Oersted’s, conflicts with Oersted’s own writings.

Without getting into the messy details, it seems apparent that Oersted speculated in front of his student audience that the current in the circuit might have an effect on a magnetic needle. There doesn’t seem to be any record of Oersted having tried out this experiment beforehand. But it begs the perplexing question of why an esteemed professor would risk his reputation by floating unverified ideas in a lecture to a group of advanced students. Maybe it was simply a maverick moment that teachers sometimes have when they share their excitement with students!

As everyone familiar with the experiment knows, Oersted noticed a slight deflection of the magnetic needle on closing the circuit. He was not particularly convinced by this observation, and did not consider it worthy of communicating to other scientists right away.

In fact, Oersted slept on this observation for almost three months. However, on 21 July, Oersted hastily dispatched printed copies of his report of the experiment to several scientists and institutions.

In the second part of this tribute, I will look at how Oersted made sense of his discovery and what was it that he did, leading up to his realisation that he had chanced upon a new scientific fact that was very significant.

Also read Part II.

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