Not many scientists would be so brave, or foolish, to try out an experiment for the first time in public, but Hans Christian Oersted did just that - and discovered electromagnetism. This year is the 150th anniversary of his death aged 73. The scientific fool Oersted was the child of a poor apothecary born on a Danish island in the Baltic in 1777. Despite no real education he achieved a scholarship to Copenhagen University where he studied science intending to become a pharmacist. He became very interested

in philosophy and in particular the idea that all the forces and effects of nature had just one source. After a spell managing a pharmacist's shop in 1801 he left Denmark to learn more about electricity excited by the journals announcing the invention of Volta's battery.

On his travels, Oersted met many scientists and picked up ideas that seemed to agree with his philosophical theories. In Paris he gave talks to support the ideas of his new heroes. He was dismayed when the French scientists demolished all their theories. He found out that his "heroes" had never tested their theories by experiment. He returned to Copenhagen with a reputation as a scientific fool who adopted wild ideas without proof.

The experimental scientist

Oersted set about rebuilding his reputation by giving public lectures on science and soon he was respected enough to earn a position at Copenhagen University. He carried out experiments in chemistry but his real interest remained electricity. Despite his experience in Paris he still thought that all forces were linked, although the theories current at the time stated that electricity, magnetism and other phenomena were not connected. Oersted found that when an electric current is passed through a wire it becomes hot so showing that electricity and heat were linked. If the wire was very thin then it glowed when carrying a current showing that electricity and light were connected. He was sure that if he used an even thinner wire he would find that it attracted a magnet such as a compass needle - but it didn't.

A public experiment

In early 1820 Oersted was booked to give a public lecture and while getting his demonstrations ready he had the idea that instead of looking for a magnetic field in the same direction as the current, perhaps the magnetic field was formed at right angles to the wire. He set up a fine wire connected to a battery and laid the wire over the glass cover of a large compass. Time ran out and he had no chance to test his idea. It was too risky to attempt the experiment in the lecture, he thought, but as he spoke he became more and more convinced that his idea was correct. He decided to give it a go. When he connected the wire to the battery he noticed the compass give a small jerk. It was too small an effect for the audience to see and they were not impressed.

It was some months before Oersted was able to return to the experiment and when he did he was able to show that a circular magnetic field surrounded a current-carrying wire. He had proved that electricity and magnetism were connected. He reported his discovery in a short paper in July 1820 and soon scientists all over Europe were copying and developing the idea. Ampere invented the solenoid or electromagnet and Faraday first invented an electric motor and then demonstrated electromagnetic induction.

The philosopher

Oersted continued with his scientific experiments. He compressed gases and liquids to show that the change in volume was proportional to pressure. Oersted did not accept Dalton's theory of atoms as hard particles and thought that at higher and higher pressures even liquids could be compressed into smaller and smaller volumes. His results were not convincing.

In 1825 he isolated a small sample of aluminium for the first time. He told Wohler about it but wasn't very interested in pursuing it any further. Wohler developed the method and became known as the discoverer of aluminium.

For the latter part of his life he returned to his love of philosophy and wrote books describing the relationship between science and beauty. His book, The Soul in Nature, was incomplete when he died in March 1851.

Websites

You can find out more about Oersted and electromagnetism at the following sites:

www.ee.umd.edu/~taylor/frame1.htm
This site is titled a "Gallery of Electromagnetic Personalities" and includes brief biographies of Oersted and other scientists involved in the electromagnetism story.

http://www-spof.gsfc.nasa.gov/Education/whmfield.html
This site tells the history of magnetism and electricity.

http://web.mit.edu/jbelcher/www/anim.html#Faraday
This site has video clips of demonstrations and simulations of important experiments in electromagnetism.

Even more on this site!

Go to questions on Oersted's life and discoveries.
Go to Teacher's Notes for more and answers to the Web activity.
Go to the Scientist of the Month Archive