André-Marie Ampère ~ Electromagnetism

For us, electromagnetism is nothing special anymore. We can find it wherever metals have to be sorted and lifted. But electromagnets also have other tasks today. Electromagnets are responsible for the friction-free floating of the trans-rapid magnetic monorail, for example. Both phenomena, electricity as well as magnetism, have been known since antiquity, but it was only at the beginning of the 19th century that a scientist was able to make a connection between the two. André-Marie Ampère was born in Polymure near Lyon in France on the 22nd of January 1775, the son of a silk dealer. Ampère was a very talented child. He was already considered a mathematical genius by the time he was 12. Self-taught, he worked from A to Z through all 20 volumes of the famous encyclopedia, compiled by Diderot and d'Alembert. Since this encyclopedia contained almost all the knowledge of the time, it is understandable that Ampère was very well educated, even though he never attended a school. At this time, his life was overshadowed by a death. His father was accused of being a monarchist during the French Revolution and was publicly executed. Young Ampère did not find it easy to cope with this blow. He fell into a deep depression and left his studies untouched for almost 18 months. Another factor was that André-Marie Ampère was suddenly penniless because the entire family fortune had been confiscated. For that reason, he started teaching mathematics at first privately and then in 1801 as a physics and mathematics teacher in the small town of Bourg-en-Bresse, north of Lyon. Just one year later, he published an essay on gambling theory, a branch of probability, with the title Considerations sur la théorie mathématique de jeu, Considerations on the Mathematical Theory of Gaming. Ampère proved that a player would always be beaten by an opponent who had much greater assets than himself. With this publication, he made a name for himself amongst the Parisian scientists. He was able to leave the small town and accept a position as a mathematics teacher at the Lyon Grammar School. In 1805, he moved to Paris, where he became a coach and then, four years later, a professor of analysis at the École Polytechnique. Here, he continued his research in many areas. Besides philosophy, psychology and metaphysics, he mainly occupied himself with chemistry, which at that time was still in its infancy. He primarily investigated the physical and chemical properties of gases. In 1814, he finally became a member of the Academy of Sciences in Paris. Now, Ampère was a recognized scientist and carried out research in many areas of chemistry and physics. Then he heard about experiments conducted by the Danish physicist Hans Christian Ørsted. In 1819, Ørsted was planning to demonstrate the heating of a wire with an electric current and also to show some magnetic experiments for which he set up a compass on a wooden stand. While he was performing his electric experiments, Ørsted noticed, much to his surprise, that every time an electric current flowed through a conductor close to the compass, the compass needle was attracted and would move. With this experiment, Ørsted was able to prove for the first time that there was a connection between electricity and magnetism. When Ampère heard about the experiments in September 1820, he was so impressed that he put all other work on hold and devoted himself entirely to research into this electric phenomenon. Ampère, considered an eccentric because of his absent-mindedness and shyness, became a different man. He even thought it possible that magnets weren't needed for this effect, but that wires in which an electric current was flowing would themselves exert a force on each other. In order to show these forces, he needed a measuring instrument. Thus, Ampère developed the electrodynamic balance. A U-shaped piece of wire, able to move freely like a pendulum, hung next to a fixed conductor. This experimental setup was intended to prove the correctness of Ampère's theory. Just one week later, he performed experiments with the electrodynamic balance. They demonstrated the interaction of two conductors through which electric currents were flowing. Ampère discovered that parallel electric conductors attracted each other when the electric current running through them was flowing in the same direction, whereas they repelled each other when the electric currents flowed in opposite directions. He thus suspected that the flow of electric current created a magnetic field around the conductor. If the current in both conductors was flowing in the same direction, the two conductors were attracted to each other, like two magnets. If the currents were flowing in opposite directions, the two conductors repelled each other. The direction of the magnetic field around a conductor through which an electric current flows can be determined by the so-called right-hand grip rule. When the thumb of the right hand is pointing in the direction of the current, then the fingers point in the direction of the magnetic field. In further experiments, Ampère discovered that if an electric conductor were to be wound up into a coil, it behaved like a bar magnet. He used a voltaic pile, a simple chemical battery as his power supply. An electric current flows through the coil, which thus has a plus and a minus pole. If the coil is suspended, it aligns itself in a north-south direction, just like a compass needle. Ampère collated the observations and results of his experiments and thus laid the foundations of a mathematical theory of electromagnetism, a term that goes back to him. For Ampère, there was no longer any doubt that magnetism and electricity could be reduced to a single law of nature. The magnetic forces can only arise when currents are in motion in a closed circuit. And the greater the intensity of the current, in other words, the larger the amount of current flowing, the greater also is the resulting magnetic force. In order to corroborate his theory, Ampère developed a measuring instrument that would display the strength of the current with a hanging magnetic needle. This invention, in an improved form, was later called an ammeter. It is one of the most important measuring instruments in electrical engineering. But Ampère went even further with his deliberations. It was his opinion that even in permanent magnets, the magnetism was not caused, as previously thought, by an indefinable magnetic fluid, but by electrical circuits in every single atom of the magnet. He assumed that every atom was incessantly being surrounded by electrons and thus small electrical circuits. Because of the consequent magnetic field, every atom behaved like a small bar magnet. In permanent magnets, they are all aligned in the same direction. In other materials, they are all aligned differently, which causes their magnetic effect to be cancelled out, and so they appear neutral to the outside. In 1826, his researches and the resulting fame led to Ampère being appointed to the chair of physics at the Collège de France in Paris. But now he became less active. Even though the Academy of Sciences had promised him a thousand francs for further research, in 1827, Ampère, who had suffered from depression from a young age, withdrew into loneliness. He devoted himself to his private mathematical and philosophical studies and did without the fame. On the 10th of June, 1836, at the age of 61, André-Marie Ampère died on an official trip to Marseille. He was buried in the family grave at Montmartre Cemetery in Paris. From August to November 1881, the First International Electrical Congress was held in the Palais de l'Industrie in Paris. The main attractions were the presentations of the latest technical achievements, such as the light bulb by Edison and the electric tram by Siemens. But the participants also discussed what standard names should be given to the electrical units. For the unit of electrical potential difference, the unit volt was chosen, in honour of the inventor of the battery, Alessandro Volta. The unit of electrical resistance was given the name ohm. At the suggestion of the German physicist Hermann von Helmholtz, the unit of electrical current was named ampere, in memory of the great achievements of Ampère the scientist. André-Marie Ampère is definitely amongst the most outstanding universal scholars of the beginning of the 19th century. Even though he only occupied himself intensively with electricity for three years, his main achievement was, without a doubt, to link the previously unconnected areas of electricity and magnetism, thus creating the basis for the further development of electrodynamics. Today there are many applications of electrodynamics, the loudspeaker being one example from everyday life. A loudspeaker is an apparatus that converts electric impulses into sound. The predominant design is the electromagnetic loudspeaker. At the heart of the dynamic loudspeaker is a coil in a magnetic field. A membrane is attached to this coil. If an electric current flows through the coil, both it and the membrane oscillate in time with the current, because, depending on the level of current, it is attracted more or less. This causes the membrane to produce sound waves, that is, it passes on the information in the form of sound. The trans-rapid magnetic monorail also makes use of the electromagnetic effect. The train is lifted off the tracks by electromagnets and thus floats frictionless above them. It is able to reach speeds of up to 500 km an hour. All this was only made possible by the basic research done by André-Marie Ampère.