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Acetic Acid: (n.) Colorless liquid whose aqueous solution is acidic. It is one of the reactants in the synthesis of isoamyl acetate, a banana flavoring.
Acid: (adj.) (from the Latin acidus) Refers to an aqueous solution with a pH less than 7. This solution contains hydrogen ions H⁺.
Adapted: (adj.) Refers to a dipole that functions normally because its nominal voltage is equal to the voltage of the generator.
Air: (n.) Mixture of several gases. On average, it consists of 20% oxygen and 80% nitrogen (and 1% other gases such as carbon dioxide).
Alchemy: (n.) (from the Arabic al-kîmiyâ) Occult science of the Middle Ages, which, based on mineral and planetary symbolism, sought to establish correspondences between the material and spiritual worlds and to discover the philosopher's stone.
Alcohol: (n.) (from the Arabic al meaning the and kohol meaning subtle thing) There are several types of alcohol. The most common is ethanol or ethyl alcohol with the formula CH₃-CH₂-OH. Ethanol is found in beverages and is used in pharmacy as a disinfectant.
Alessandro Volta (1745-1827): Italian physicist. In 1792, he understood the importance of Galvani's discovery and replicated his experiments. His research allowed him to draft an electrical classification of metals (1793) and led to the invention of the electric battery. He gave his name to the unit of electrical potential difference.
Alloy: (n.) Substance with metallic characteristics that can be considered a metal containing a certain proportion of impurities. It can be a well-defined compound, a heterogeneous mixture, or any combination of metals. The most common are those of iron (special steels), copper (bronze, brass, copper-nickel, German silver), lead (antifriction), and aluminum (aluminum bronze, Duralumin, Alpax). Light alloys are mainly based on aluminum and magnesium.
Alpax: (n.) Alloy of aluminum and silicon that is easily molded.
Alternating Voltage: (n.) Voltage that varies, taking alternately positive and negative values.
Alternating: (adj.) Refers to anything that successively takes positive and then negative values. In electricity, the most common example is the mains voltage, whose value changes sign 100 times per second, going from 330 V to -330 V and then from -330 V to 330 V, and so on.
Alternator: (n.) Generator of alternating voltage. It consists of magnets rotating in front of coils. It operates on the principle of induction. By moving a magnet in front of a coil, an induced current is created in the coil. This phenomenon is exploited in power plants. Car engines have alternators to continuously recharge the battery. While the engine is running, the alternator is driven by a belt connected to the engine.
Aluminum Brass: (n.m.) Copper containing a small amount of aluminum.
Aluminum Bronze: (n.m.) Alloy of copper and aluminum, containing 4 to 13% aluminum by mass.
Aluminum: (n.) Atom with atomic number Z equal to 13. It has 13 electrons. Its symbol is Al. Aluminum is a white-gray metal, very light, ductile, and malleable, with little alteration in air. Its melting point is 660°C. Its boiling point is 2270°C. Its density is 2.6 kg/L. It is used in the manufacture of household items, due to its lightness, pure or in alloys (Duralumin, Alpax, etc.) in the automotive and aeronautics industries, and in the electrical industry.
Ammeter: (n.) Device for measuring the intensity of electric current. It is connected in series with the dipole being studied, meaning in the same branch as the dipole being studied. Since the intensity is the same at every point in a branch of an electrical circuit, the position of the ammeter in the branch does not matter, and we accurately measure the intensity of the current passing through the components of this branch.
Ampere: (n.) Legal unit of current intensity (Symbol A).
Amplitude: (n.) Maximum value of a quantity that varies periodically. In the case of mains voltage, the amplitude is 330 V.
Ampère, André-Marie (1775-1836): French scientist. Author of works in mathematics (Considerations on the Mathematical Theory of Games, 1802) and chemistry. He became famous from 1820 for his discoveries in the field of electromagnetism and electrodynamics. He built a theory in which he introduced particulate currents and gave the formula for the reciprocal action of currents. He was the first to have the idea of current intensity and used a quantity in his calculations that bears his name.
Anders Celsius (1701-1744): Swedish astronomer and physicist who participated in the first expedition to Lapland to measure the terrestrial meridian and proposed a temperature scale of 100 degrees. The point 0°C is the boiling temperature of pure water, and the point 100°C is the freezing temperature of pure water.
Anhydrous Copper Sulfate: (n.) A solid used to perform the water identification test. In the presence of water, anhydrous copper sulfate turns blue.
Anhydrous: (adj.) Does not contain water. Without water.
Anion: (n.) Negatively charged ion. It is an atom or a group of bonded atoms that has gained one or more electrons. The chloride ion Cl^- is a chlorine atom Cl that has gained an electron. The phosphate ion PO₄^3- is the group of bonded atoms PO₄ that has gained 3 electrons.
Antifriction: (n.) Alloy based on antimony, used to make the bearings of machine journals to reduce friction.
Aqueous: (adj.) Refers to a liquid solution mainly containing water.
Archimedes (287-212 BC): Ancient scholar, born in Syracuse. He found the formulas for the surface area and volume of the cylinder and the sphere, invented various mechanical devices: lever, pulley, endless screw, gear wheel. He held off the Romans besieging Syracuse for three years. It is said that he had found, using mirrors reflecting and concentrating solar light, a way to set fire to enemy boats from a distance. When the city was taken, Marcellus, the Roman general, gave orders to spare the great man. But the latter, absorbed in the research of a problem, did not notice the capture of the city, and was killed by a soldier who, not knowing him, became irritated at not being able to get any answer from him. A circumstance in Archimedes' life is related to the discovery of a fundamental principle of hydrostatics. Hiero, king of Syracuse, suspected a goldsmith who had made him a gold crown of having alloyed it with silver. He consulted Archimedes on how to discover this fraud while keeping the crown intact. The illustrious scholar reflected on it for a long time, until the day when, in his bath, he noticed that his limbs, immersed in water, lost part of their weight. Thus was found Archimedes' principle: Any body immersed in a fluid experiences a vertical buoyant force, directed upwards, equal to the weight of the displaced fluid. In the enthusiasm of this discovery, he got out of the bath and ran into the street shouting: "Eureka! Eureka! I have found it, I have found it."
Artificial Chemical Species: (n.) A chemical species that does not exist in nature.
Astronomical Unit: (n.f.) Average distance from the Sun to the Earth, which is 150 million kilometers (1.5 × 10¹¹ meters).
Atmosphere: (n.) Gaseous layer surrounding the Earth.
Atmosphere: (n.) Unit of pressure (Symbol atm). 1 atm = 1,013 hPa.
Atom: (n.) "Very small bricks" constituting the matter around us. There are a little over a hundred atoms that are listed in the periodic table of elements or Mendeleev's table. Atoms are invisible. Modern physics has revealed the internal structure of the atom. It has a nucleus at its center composed of a certain number of neutrons and protons. At its periphery, electrons, which like the eight planets around the Sun, revolve around the nucleus. The nucleus plus electrons ensemble is globally neutral.
Atomic nucleus: (n.m.) The central part of an atom, positively charged and constituting almost the entire mass of the atom. It is composed of positively charged protons and neutrons.
Attraction by a Magnet: (n.) Magnetic action used to identify the metal iron and its alloys.
Attractive Action: (n.) Action directed towards the object exerting the action.