Pratique du Shadowing: 2.7K - Apprendre l'anglais à l'oral avec la vidéo
Création de la leçon...
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In 1827, a German high school teacher discovered what he called a pure law of nature.
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But when he published his findings, he was first ridiculed, then completely ignored.
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One professor said it was a web of naked fancies, and the result of an incurable delusion.
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Another said it was an unmistakable failure, and that anyone who preached such heresies was unworthy to teach science.
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The criticism got so bad, he eventually resigned his position and moved to another city 400 kilometers away.
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About 15 years later though, the Royal Society of London would recognize his work and award him the Copley Medal,
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essentially equivalent to the modern Nobel Prize.
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And today, this same law is taught to teenagers across the world as the fundamental principle of electronics.
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Georg Ohm was born in 1789 in Erlangen, Bavaria to a modest working-class family.
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His father was a locksmith who had no formal education but loved math and philosophy with a deep passion.
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He educated himself to such a high degree
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that he was able to provide an excellent education to Georg and gave him a strong foundation in both math and science.
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Eventually, in 1804, Ohm went off to study at the University of Erlangen.
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This would last only three semesters, though.
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While attending university, he spent much of his time pursuing non-academic interests, to the dismay of his father,
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who withdrew his financial support and forced his son to drop out.
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Over the next decade or so, Ohm took up a wide number of math teaching posts in various cities across modern-day Switzerland and Germany.
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He was eventually able to finish his university degree
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and settled into a permanent role as a high school science teacher at the Jesuit Gymnasium of Cologne,
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a top-rated institution that was better than any Ohm had previously taught in.
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Most importantly, the school had something that Ohm would use to dramatically alter his life, a well-funded laboratory.
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Ohm began his teaching position in 1817.
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Around this point in history, the theory of static electricity was well developed.
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The understanding of moving charges, or current on the other hand, was still in its early stages.
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The units of a volt or an amp did not exist yet, and there was no consistent calibrated way to measure current.
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The prevailing idea about observed electric forces was that they consisted of the action of some sort of electrical fluid.
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There were three discoveries in the early 1800s, though, that fundamentally changed this understanding of electricity.
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And while Ohm initially used his school's lab as an aid to teaching, these three discoveries also convinced him to devote his spare time conducting research in the lab.
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And it enabled him to systematically study and experiment with electricity.
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The first of these discoveries was the battery, invented by an Italian scientist named Alessandro Volta in 1800.
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Volta provided a convenient, relatively easy way for scientists to create a continuous flow of electricity.
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All one had to do was take a stack of alternating copper and zinc plates.
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Between each layer, place a piece of cloth soaked in brine.
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This would generate an electric force.
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and by connecting the top and bottom plates with a wire, an electric current would be produced.
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Volta's invention came to be called the voltaic pile and it was pivotal in the process of understanding what electricity is.
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Before this, scientists were only able to create temporary sparks.
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Now, scientists of all kinds were able to create a continuous electric current
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and use it to conduct experiments in entirely new ways.
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The voltaic pile would eventually allow Michael Faraday to conduct his famous experimental work
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that would lead to the four equations of electromagnetism.
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But before that, there was another pivotal discovery by the Danish scientist Hans Christian Orsted.
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In 1820, after setting up a voltaic pile, Orsted placed a magnetic compass nearby.
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To his surprise, he saw that the needle moved.
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After repeating the experiment several times with magnets in various locations, he observed that the magnets formed a circle around the wire.
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Somehow the current flowing through the wire was causing a magnetic force around it.
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The first link between electricity and magnetism was discovered.
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Both Folta's and Orsted's discoveries played a pivotal role in Ohm's initial experiments with electricity.
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The third discovery, which I'll mention shortly, provided the final solution to some of the difficulties Ohm encountered along the way.
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Ohm began his experimental studies by first deciding to study the conductivity of various metals.
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Most scientists at the time were convinced that the voltage in a battery
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and the current that flowed in a wire were completely independent phenomena.
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Ohm believed otherwise.
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He was convinced that the two were linked by some physical law and he was determined to discover it.
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He began by setting up a voltaic pile and connecting it to a torsion balance, an early form of an ammeter.
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Essentially it consisted of a magnetic needle that would move more or less strongly depending on the strength of the current.
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He experimented with wires of different materials like copper, gold, silver, and brass.
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He also varied the lengths of wires, but made sure all of them had the same diameter.
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Ohm found that the following materials with their corresponding lengths were all equally conductive,
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but he couldn't find the deeper connection between voltage and current that he was really after.
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The reason?
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His source of power, the voltaic pile.
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Though Volta's invention provided a much needed advance in providing a continuous current to scientists at the time, the performance of these batteries was anything but perfect.
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The current quickly dissipated over time.
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In fact, when Ohm conducted his experiment, he used the standard wire as his control
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and then he would switch various wires in
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and compare the current strength with it versus the current strength with the standard wire.
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There was a big problem though.
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The standard wire kept experiencing a smaller and smaller current over time.
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He decided to attempt to calculate what he termed as the loss of force here, and he came up with this equation.
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But after making slight adjustments and repeating this experiment a few times in different ways,
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he realized he needed a better method.
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The rate of decay of the battery was just too unpredictable, and the equation he initially found didn't consistently fit the data.
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At the suggestion of a colleague named Johann Christian Paggendorf, He decided to replace the voltaic pile with a thermocouple.
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This was the third key discovery that enabled Ohm to make his own scientific breakthrough.
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Now, before I explain how the thermocouple led to Ohm's breakthrough, I'd like to take a minute to thank this video's sponsor, Odoo.
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Now back to the thermocouple.
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The thermocouple was discovered by a German physicist named Thomas John Seebeck in 1822.
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Seebeck found that if he made a circuit with two different metals, he could cause a magnetic needle to be deflected.
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In other words, he could produce a steady electric current.
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Crucially though, this only occurred when there was a temperature difference between the two.
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So one metal had to be either heated up or cooled.
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Heating would cause the needle to go in one direction, whereas cooling resulted in a deflection in the opposite direction.
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In order to use a thermocouple as his power source, Ohm had to slightly change his experimental setup.
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He began by creating his own thermocouple with bismuth and copper.
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He then placed two containers underneath, one filled with boiling water and the other filled with ice.
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This created a constant 100 degree temperature difference between the two.
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Finally, he connected all of this to two cups filled with mercury, and he also attached a torsion balance to measure the strength of current again.
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The cups of mercury were the means by which he connected the circuit.
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When he would place a wire inside the cup, the circuit would close and current would flow.
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When he removed it, the circuit would open and the current would stop.
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The thermocouple was exactly what he needed.
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It provided a continuous, reliable current.
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He then tested eight wires of varying lengths and recorded the deflection of the needle for each one.
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He found the following results.
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Ohm then stated that the above numbers can be represented very satisfactorily by the equation x equals a over b plus x.
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Where big x is the strength of the magnetic effect of the wire, little x is the length of the wire, and according to him, a and b are constants
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that depend on the exciting force and resistance of the remaining parts of the circuit.
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In other words, a and b depended on both the wire's material and the source of power.
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He then decided to make the temperature difference smaller to see how this would affect his results.
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He found that B was not affected at all by this change, but A was.
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Ohm concluded that A depended purely on the exciting force and B depended purely on the resistance of the circuit.
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He had just discovered what we today call Ohm's law.
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In modern notation, we call the magnetic effect the current, A the voltage, and the denominator here is the resistance.
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Ohm wrote up all these results in a paper published in 1826, but he wasn't done just yet.
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You see, a few years prior to this, a French mathematician by the name of Joseph Fourier published a revolutionary book on heat that included,
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among other things, the invention of Fourier series and the heat equation.
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Ohm had been deeply impressed by Fourier's work
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and wanted to provide the same type of rigorous mathematical framework to the physical law he'd just discovered through experiment.
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He spent the next year developing a purely mathematical theory that made very little reference to his experiments.
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He then published his new theory in 1827 in a book titled The Galvanic Circuit Investigated Mathematically.
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In it he described electricity very much like Fourier described heat.
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And he even mathematically derived a new version of his law that looks even more like the modern version today.
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But as I mentioned at the beginning of the video, this work was not well received by the scientific community surrounding Ohm.
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A prominent professor in Berlin named Heinrich Wilhelm Dov said it was a naked web of fancies.
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Another Berlin professor named Georg Friedrich Pohl called it an unmistakable failure
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and even convinced the German minister of education to pressure Ohm to resign, which he ultimately did.
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All this occurred for many reasons, but to give you a bit of insight into why this seemingly strange situation came about,
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here are two factors that played a significant role.
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First, most German physicists at the time were philosophically opposed to mathematically deductive physical theories.
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They thought it wasn't an accurate way to discover and understand the laws of physics.
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What they preferred instead was a focus on performing experiments and letting experimental results guide their understanding of theory.
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It seems that the later mathematical theory that Ohm developed was the primary contact many had with his work,
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and they were unaware of his earlier experimental results.
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As a consequence, they simply did not appreciate its emphasis on math and lack of contact with experiment.
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The second reason was the way in which Ohm wrote.
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He seems to have lacked the ability to communicate his ideas in a clear way that others could understand.
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Though he began his treatise explaining all the math he was using, most of it was just completely unfamiliar and confusing to his readers.
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As one author wrote about Ohm's book, in neither the introduction nor the body of the work did
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Ohm bring decisively home either the underlying unity of the whole or the connections between fundamental assumptions and major deductions.
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After being forced to resign from his permanent position in Cologne, Ohm took up various temporary teaching positions at schools in Berlin.
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Eventually, in 1833, he was able to become a professor at Nuremberg Polytechnic.
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It was only after scientists from other countries discovered Ohm's work
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and began promoting it that he finally got the recognition that he deserved.
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In particular, William Sturgeon and Charles Wheatston, two scientists from England who promoted Ohm's ideas,
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as well as Claude Pouillet from France who independently confirmed Ohm's results.
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This eventually led to proper recognition in his homeland as well.
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In June 1839, he became a member of the Prussian Academy of Sciences.
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Then in 1841, he was given the Copley Medal by the Royal Society in London, essentially the Nobel Prize of his day.
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And finally in 1852, he achieved something that was his lifelong ambition.
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He was appointed the Chair of Physics at the University of Munich,
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which he sadly would hold for just two years as he passed away in 1854 due to a stroke.
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Years after his death, he would receive an honor that would make him ever present in the scientific community.
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In 1881, when the International Congress in Paris was establishing a system of electric units.
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They defined the amp, the volt, and the ohm.
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To this day,
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this unit of measurement together with Ohm's law are used by millions of students worldwide as the cornerstone of analyzing electrical circuits.
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If you'd like to see more videos like this, join my Patreon community and support the channel by clicking right here.
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And thank you to all the generous patrons who make these videos possible.
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Thank you.
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Vocabulaire et conseils d’expression pour cette leçon
Cette vidéo contient 162 phrases et 2412 mots à répéter en shadowing. La partie parlée dure 15:37. Le locuteur parle à un rythme naturel d’environ 155 mots par minute, proche d’une conversation courante. Seuls 77 % des mots font partie des 3 000 mots les plus courants en anglais, le vocabulaire est donc exigeant.
Vocabulaire clé de cette vidéo
15 mots moins courants de la vidéo, avec leur prononciation et leur sens :
- wire /ˈwaɪɚ/ (nom) — fil. Metal formed into a thin, even thread, now usually by being drawn through a hole in a steel die.
- experiment /ɪkˈspɛɹ.ə.mənt/ (nom) — expérience. A test under controlled conditions made to either demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy or likelihood of…
- discovery /dɪˈskʌv.ɹi/ (nom) — découverte. Something discovered.
- magnetic /mæɡˈnɛtɪk/ (adjectif) — magnétique. Of, relating to, operating by, or caused by magnetism.
- pile /paɪl/ (nom) — monceau, tas. A mass of things heaped together; a heap.
- experimental /ɪkspɛɹəˈmɛntəl/ (adjectif) — expérimental. Pertaining to or founded on experiment.
- mathematics /mæθ(.ə)ˈmæt.ɪks/ (nom) — mathématiques. An abstract representational system studying numbers, shapes, structures, quantitative change and relationships between them.
- equation /ɪˈkweɪ.ʒən/ (nom) — équation. The act or process of equating two or more things, or the state of those things being equal (that is, identical).
- needle /ˈniː.dəl/ (nom) — aiguille. A long, thin, sharp implement usually for piercing as in sewing, embroidery, acupuncture, tattooing, body piercing, medical injections, sutures, etc; or a…
- convince /kənˈvɪns/ (verbe) — convaincre, persuader. To make someone believe, or feel sure about something, especially by using logic, argument or evidence.
- continuous /kənˈtɪn.juː.əs/ (adjectif) — continu, continuel. Without stopping; without a break, cessation, or interruption.
- depend /dɪˈpɛnd/ (verbe) — dépendre. To be contingent or conditioned; to have something as a necessary condition
- essentially /ɪˈsɛnʃəli/ (adverbe) — essentiellement, en essence. In essence: by nature.
- copper /ˈkɒpə/ (nom) — cuivre. A reddish-brown metallic chemical element (symbol Cu) with the atomic number 29; also, the metal made up of this element.
- invention /ɪnˈvɛnʃən/ (nom) — invention. Something invented.
Les verbes à particule que vous entendrez
- set up /ˌsɛt ˈʌp/ (verbe) — mettre en place, installer. To make ready for use.
- come about (verbe) — se passer. To come to pass; to develop; to occur; to take place; to happen; to exist.
- come up with (verbe) — inventer, imaginer. To manage to produce, deliver, or present (something) by inventing, creating, thinking of, or obtaining it.
- heat up (verbe) — chauffer. To heat, to cause to become hotter.
Prononciation à surveiller
Le locuteur utilise 8 contractions et formes réduites, comme wasn't, couldn't, didn't. Prononcez-les sous leur forme courte, telles que vous les entendez.
- Les sons « th »: mathematics /mæθ(.ə)ˈmæt.ɪks/, mathematical /ˌmæθ(.ə)ˈmæt.ɪ.kəl/, breakthrough /ˈbɹeɪk.θɹuː/, underneath /ˌʌndɚˈniθ/, withdraw /wɪðˈdɹɔ/
- Les sons « sh » et « zh »: equation /ɪˈkweɪ.ʒən/, essentially /ɪˈsɛnʃəli/, invention /ɪnˈvɛnʃən/, recognition /ˌɹɛkəɡˈnɪʃ(ə)n/, shortly /ˈʃɔɹtli/
- Mots longs — placez bien l’accent: experiment /ɪkˈspɛɹ.ə.mənt/, electricity /ɪˌlɛkˈtɹɪsɪti/, experimental /ɪkspɛɹəˈmɛntəl/, mathematics /mæθ(.ə)ˈmæt.ɪks/, continuous /kənˈtɪn.juː.əs/
Comment s’entraîner avec cette vidéo
- Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
- Commencez à la vitesse 0,75×, répétez phrase par phrase, puis revenez à la vitesse normale quand cela devient facile.
- Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme wire, experiment, discovery.
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.