Hans Christian Oersted and Electromagnetism


By Robert Hazen, Ph.D.George Mason University

The beginning of electricity’s modern era can be traced to a small Danish college classroom in 1820. There, in front of a room full of physics students, it was Professor Hans Christian Oersted who discovered that electricity can produce magnetic fields. And this was a transforming event in the science of electromagnetism. But how did this happen?

A drawing of a man doing an experiment with static electricity.
The study of electricity was quite popular in the early 1800s. (Image: Laplante/Public domain)

Who Was Hans Christian Oersted?

Hans Christian Oersted was born in 1777. He was the elder son of a Danish pharmacist, and from an early age, he had planned to follow his father’s profession of pharmacy. But he became captivated by electrical studies in 1800, shortly after Volta’s announcement of the battery.

The young Hans Oersted excelled as a student in languages, mathematics, and science. He was home-schooled, but he passed the entrance examinations and enrolled in the University of Copenhagen in 1794 at the young age of 17. He received degrees in both pharmacology and in Kantian philosophy, of all things. And he was, for a short time thereafter, a manager of a pharmacy. But eventually he turned his attention full time to science; that was his real love.

Learn more about the invention of the battery.

Oersted’s Beginnings in the Study of Electricity

While still in his 20s, Oersted secured visits to many of the famous laboratories in Europe, and he was able to learn the types of research that was going on there. He also was able to gain entrance to these laboratories and gain respect because he himself invented an improved compact battery, a battery that was quite powerful, but small and portable.

He returned to Denmark in 1804, and turned to public lecturing, where he did scientific demonstrations for the public on electrical phenomena. He was so successful and popular that he was given a professorship almost by demand at the University of Copenhagen in 1806 because he was so good at bringing science to the public.

The Needle Twitches

Oersted believed that the various forces in nature, including magnetism and electricity, must somehow stem from the same original power. He saw a unity in the universe and its forces. He was, therefore, predisposed to observe links between electricity and magnetism that other people might not have seen.

So, it was in the winter of 1820 that Oersted made his most famous discovery. He was performing demonstrations  in  electricity  and magnetism in front of his classroom. He hooked up a coil of wire to a battery and passed a current through that coil of wire, and he observed  that a compass needle next to the coil twitched whenever he did this.

Electrical Magnetic Fields

A portrait of Hans Christian Oersted.
Before Oersted’s discovery, magnetism and electricity were thought to be separate phenomena. (Image: Unknown author/Public domain)

After several weeks of experimentation, Oersted announced that electricity passing through a curved path produces a magnetic field. By July of 1820, he had submitted a manuscript describing this  link  between  electricity  and magnetism, and this was the great discovery of the fact that electricity produces magnetic fields.

Prior to Oersted, electricity and magnetism were viewed as two completely separate phenomena. They involved very different kinds of physical situations and conditions, but here Oersted unified this work by showing that one phenomenon was infinitely linked to the other.

This is a transcript from the video series The Joy of ScienceWatch it now, on Wondrium.

Energy Conversions

With the battery, of course, you could convert electrical potential energy into chemical potential energy. That’s the decomposition of water and heat and light. Oersted showed that you could also convert that into magnetic potential energy. So, another kind of energy conversion was brought forth in the scientific world.

Oersted’s discovery led to a number of important inventions quite quickly because it provided a way to convert this electrical potential energy into other forms of energy. Of course, first magnetic energy, but then you also could use magnetic energy to produce kinetic energy.

The Electromagnet

The first and most obvious of the advances was just the electromagnet. You can use a coil of wire. So this is a continuous long loop of wire that you’ll see in various electromotors. And if you close the circuit, you can then create a magnet just out of a loop of wires—an astonishing effect.

You can go one step further. You can take those coils of wire, and you can wrap them around so they create an electromagnet that attracts a clapper, a piece of metal. And, therefore, you can create a buzzer just by closing the circuit. So that was the principle of the buzzer and various other kinds of sound-making devices.

The same principle, by the way, is used in the telegraph. You have electromagnets that open and close circuits. If you open and close a circuit at your end with long and short pulses, those pulses go through the wire and open and close circuits at the far end, and the same series of long and short pulses is transmitted long distances over a wire.

Learn more about electromagnetism.

Electric Motors

And then we come to electric motors. Electric motors are a pervasive use   of electromagnets in our society, an incredibly profound ability to convert electrical energy, through magnetic energy, into kinetic energy.

In a motor, you simply have a push-pull effect  of one set of magnets against another. In many simple electric motors—for example, the kind you will find in most electric razors—you’ll find permanent magnets, which are fixed into the casing of the motor, and then you’ll have a rotor, which has little coils of wire, which form electromagnets.

As the current flows through these, you get a push-pull effect, and that spins the rotor because magnetic opposites attract, but the same poles repel each other. And by a very careful alternation of opposite and like poles, you can get this push-pull effect causing a rotor to work.

The number of applications of electromagnetism in everyday life is huge. And all this developed from a discovery made when Oersted noticed a compass needle twitch.

Common Questions about Hans Christian Oersted

Q: What did Hans Christian Oersted study?

Hans Christian Oersted received degrees in both pharmacology and in Kantian philosophy.

Q: How did Oersted manage to visit famous laboratories in his youth?

Oersted was able to gain entrance to many famous European laboratories because he himself invented an improved compact battery, a battery that is quite powerful, but very small and portable.

Q: How did Oersted discover that electricity created a magnetic field?

While performing demonstrations in electricity and magnetism in front of his classroom, Oersted hooked up a coil of wire to a battery and passed a current through that coil of wire. He observed that a compass needle next to the coil twitched whenever he did this. Further experiments led to the discovery that electricity flowing in a curve creates a magnetic field.

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