How was electromagnetism discovered

Discovery 200 years agoHans-Christian Oersted and electromagnetism

"Dear people present and absent! When you listen to the radio, remember how people came into possession of this wonderful tool of communication."

August 1930. Albert Einstein opens the German Radio Exhibition in Berlin with a speech and recalls some of the pioneers of radio technology. Above all: a Danish scholar and natural philosopher.

"Think of Oersted, who first noticed the magnetic effect of electric currents."

Important basis of power generation

In 1820, Hans Christian Oersted published a discovery that was astonishing at the time: electricity and magnetism are not independent natural phenomena, but belong together - the discovery of electromagnetism. It was to have a decisive influence on physics and technology: Oersted's discovery became an important basis for power generation, electric motors and broadcast technology.

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Hans Christian Oersted, born in August 1777 as the son of a pharmacist on the Danish island of Langeland, began studying natural sciences in Copenhagen at the age of 16, did his doctorate on the natural philosophy of Immanuel Kant and went on a multi-year study trip through Europe.

The search for the foundations of nature

In 1804 he returned to Copenhagen to settle down professionally. Oersted's fascination was the search for the foundations of nature. It must be structured systematically, he believed, and there should be a certain uniformity behind everything.

"Physics has never attracted greater interest than it does today. We are facing a more powerful renaissance than we have ever seen in history."

The Danish royal family provided the scholars with a collection of physical and chemical instruments and an annual budget of 600 Reichstalers. This allowed Oersted to devote himself to one of his favorite questions: Were electricity and magnetism two independent fields of knowledge, as many believed at the time? Or were they just two versions of the same phenomenon? One indication of the latter was Oersted's observation that a compass is affected by lightning strikes.

"I noticed the swaying of the magnetic needle during a thunderstorm, and I suspected that an electrical discharge might affect the experiment."

Hans Christian Oersted received extensive support from the Danish royal family during his time (picture alliance / akg)

A phenomenon which the Danish physicist confirmed in his assumption.

"Just as a body charged with a strong electric current gives off light and heat at any time, it could also radiate the assumed magnetic effect in a similar way."

In order to test the hypothesis, Oersted experimented with a very simple experimental set-up: He connected the two ends of a metal wire to a battery, which caused current to flow through the wire. Then he held a compass needle close by - and observed the needle trembling slightly. At first, however, Oersted was not entirely sure of his case.

"The effect was certainly unmistakable, but it still seemed so confusing to me that I postponed further investigations until I was hoping to have more leisure."

That time came in the summer of 1820. Now Oersted was able to refine and make his experiment more precise. In the end it was clear: the effect was reproducible, the current in the wire clearly deflected the magnetic needle. On July 21, 1820, the then 42-year-old put his observation on paper.

"In the month of July 1820, through continued experiments for a few days, I discovered the fundamental law of electromagnetism, namely that the magnetic action of the electric current has a circular motion around it."

A lightning strike gave Hans Christian Oersted the idea that magnetism and electricity are related (Ensio Ilmonen / dpa)

Thousands commemorated Oersted's death

That means: The magnetic field runs in circles around the wire - a finding that would later be the prerequisite for the construction of electric motors and radio transmitters. The news of Oersted's discovery quickly spread across Europe and prompted further pioneering experiments. In the same year, André Marie Ampère showed in Paris that two wires through which current flows magnetically attract or repel each other - definitive proof that it is the flow of electrical current that is behind the magnetism. In any case, Oersted became famous for his discovery. When he died in 1851, thousands of Danes remembered him in a candlelight procession. And later some things were named after him - a lunar crater, a satellite and a physical unit.