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History Of Electromagnetic Theory
The history of electromagnetic theory begins with ancient measures to understand atmospheric electricity, in particular lightning. People then had little understanding of electricity, and were unable to explain the phenomena. Scientific understanding and research into the nature of electricity grew throughout the eighteenth and nineteenth centuries through the work of researchers such as André-Marie Ampère, Charles-Augustin de Coulomb, Michael Faraday, Carl Friedrich Gauss and James Clerk Maxwell. In the 19th century it had become clear that electricity and magnetism were related, and their theories were unified: wherever charges are in motion electric current results, and magnetism is due to electric current.Lyons, T. A. (1901). ''A treatise on electromagnetic phenomena, and on the compass and its deviations aboard ship. Mathematical, theoretical, and practical''. New York: J. Wiley & Sons. The source for electric field is electric charge, whereas that for magnetic field is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Electricity
Atmospheric electricity describes the electrical charges in the Earth's atmosphere (or that of another planet). The movement of charge between the Earth's surface, the atmosphere, and the ionosphere is known as the global atmospheric electrical circuit. Atmospheric electricity is an interdisciplinary topic with a long history, involving concepts from electrostatics, atmospheric physics, meteorology and Earth science. Thunderstorms act as a giant battery in the atmosphere, charging up the electrosphere to about 400,000 volts with respect to the surface. This sets up an electric field throughout the atmosphere, which decreases with increase in altitude. Atmospheric ions created by cosmic rays and natural radioactivity move in the electric field, so a very small current flows through the atmosphere, even away from thunderstorms. Near the surface of the Earth, the magnitude of the field is on average around 100 V/m, oriented such that it drives positive charges down. Atmospheric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lodestone
Lodestones are naturally magnetization, magnetized pieces of the mineral magnetite. They are naturally occurring magnets, which can attract iron. The property of magnetism was first discovered in Ancient history, antiquity through lodestones. Pieces of lodestone, suspended so they could turn, were the first magnetic compasses, and their importance to early navigation is indicated by the name ''lodestone'', which in Middle English means "course stone" or "leading stone", from the now-obsolete meaning of '':wikt:lode, lode'' as "journey, way". Lodestone is one of only a very few minerals that is found naturally magnetized. Magnetite is black or brownish-black, with a metallic lustre (mineralogy), luster, a Mohs scale of mineral hardness, Mohs hardness of 5.5–6.5 and a black streak (mineralogy), streak. Origin The process by which lodestone is created has long been an open question in geology. Only a small amount of the magnetite on the Earth is found magnetized as lodest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Eel
The electric eels are a genus, ''Electrophorus'', of neotropical freshwater fish from South America in the family Gymnotidae, of which they are the only members of the subfamily Electrophorinae. They are known for their electric fish, ability to stun their prey by generating electricity, delivering shocks at up to 860 volts. Their electrical capabilities were first studied in 1775, contributing to the invention of the electric battery in 1800. Despite their name, electric eels are not closely related to the true eels (Anguilliformes) but are members of the electroreceptive knifefish Order (biology), order Gymnotiformes. This order is more closely related to catfish. In 2019, electric eels were split into three species: for more than two centuries before that, the genus was believed to be monotypic, containing only ''Electrophorus electricus.'' They are nocturnal, obligate air-breathing animals, with poor vision complemented by Electroreception and electrogenesis#Electrolocati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Catfish
Electric catfish or Malapteruridae is a family of catfishes (order Siluriformes). This family includes two genera, '' Malapterurus'' and '' Paradoxoglanis'', with 21 species. Several species of this family have the ability to generate electricity, delivering a shock of up to 350 volts from its electric organ. Electric catfish are found in tropical Africa and the Nile River. Electric catfish are usually nocturnal and carnivorous. Some species feed primarily on other fish, incapacitating their prey with electric discharges, but others are generalist bottom foragers, feeding on things like invertebrates, fish eggs, and detritus. The largest can grow to about 1.2 meters (3 ft) long, but most species are far smaller. Description The Malapteruridae are the only group of catfish with well-developed electrogenic organs; however, electroreceptive systems are widespread in catfishes. The electrogenic organ is derived from anterior body musculature and lines the body cavity. Electric c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Fish
An electric fish is any fish that can Bioelectrogenesis, generate electric fields, whether to sense things around them, for defence, or to stun prey. Most fish able to produce shocks are also electroreceptive, meaning that they can sense electric fields. The only exception is the Uranoscopidae, stargazer family (Uranoscopidae). Electric fish, although a small minority of all fishes, include both oceanic and freshwater species, and both cartilaginous and bony fishes. Electric fish produce their electrical fields from an Electric organ (biology), electric organ. This is made up of electrocytes, modified muscle or nerve cells, specialized for producing strong electric fields, used to locate prey, for Anti-predator adaptation, defence against predators, and for Signalling theory, signalling, such as in courtship. Electric organ discharges are two types, pulse and wave, and vary both by species and by function. Electric fish have evolved many specialised behaviours. The predatory Cla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient Egypt
Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower Egypt were amalgamated by Menes, who is believed by the majority of List of Egyptologists, Egyptologists to have been the same person as Narmer. The history of ancient Egypt unfolded as a series of stable kingdoms interspersed by the "Periodization of ancient Egypt, Intermediate Periods" of relative instability. These stable kingdoms existed in one of three periods: the Old Kingdom of Egypt, Old Kingdom of the Early Bronze Age; the Middle Kingdom of Egypt, Middle Kingdom of the Middle Bronze Age; or the New Kingdom of Egypt, New Kingdom of the Late Bronze Age. The pinnacle of ancient Egyptian power was achieved during the New Kingdom, which extended its rule to much of Nubia and a considerable portion of the Levant. After this period, Egypt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetism
In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interactions of atoms and molecules. Electromagnetism can be thought of as a combination of electrostatics and magnetism, which are distinct but closely intertwined phenomena. Electromagnetic forces occur between any two charged particles. Electric forces cause an attraction between particles with opposite charges and repulsion between particles with the same charge, while magnetism is an interaction that occurs between charged particles in relative motion. These two forces are described in terms of electromagnetic fields. Macroscopic charged objects are described in terms of Coulomb's law for electricity and Ampère's force law for magnetism; the Lorentz force describes microscopic charged particles. The electromagnetic force is responsible for ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malapterurus Electricus 1
''Malapterurus'' is a genus of catfishes (order Siluriformes) of the electric catfish family (Malapteruridae). It includes 18 species. Distribution The genus ''Malapterurus'' is found throughout western and central tropical Africa and the Nile River. They occur in all major freshwater systems including the Buzi, Niger, Ogooué, Omo, Sanaga, Sabi-Lundi, Senegal, Shari, Congo, and Zambezi River basins, as well as Lakes Albert, Chad, Kainji, Tanganyika, and Turkana. Description ''Malapterurus'' have an elongate and cylindrical body that gives them the general appearance of a sausage. The eyes are small, the lips are rather thick, and the snout is rounded with widely separated nostrils. The gill openings are narrow and restricted to the sides. ''Malapterurus'' species have three pairs of barbels, and lack a dorsal fin. The pectoral, pelvic, and caudal fins are rounded. The swimbladder has two elongate posterior chambers. Species in ''Malapterurus'' are generally grayish-brow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Literature
The history of Chinese literature extends thousands of years, and begins with the earliest recorded inscriptions, court archives, building to the major works of philosophy and history written during the Axial Age. The Han dynasty, Han (202 BC220 AD) and Tang dynasty, Tang (618–907 AD) dynasties were considered golden ages of poetry, while the Song dynasty, Song (960–1279) and Yuan dynasty, Yuan (1271–1368) were notable for their lyrics (''ci''), essays, dramas, and plays. During the Ming dynasty, Ming and Qing, mature novels were written in written vernacular Chinese, an evolution from the preeminence of Literary Chinese patterned off the language of the Chinese classics. The introduction of widespread woodblock printing during the Tang and the invention of movable type printing by Bi Sheng (990–1051) during the Song rapidly spread written knowledge throughout China. Around the turn of the 20th century, the author Lu Xun (1881–1936) is considered an influential voi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomancy
Geomancy, a compound of Greek roots denoting "earth divination", was originally used to mean methods of divination that interpret geographic features, markings on the ground, or the patterns formed by soil, rock (geology), rocks, or sand. Its definition has expanded over time (along with the recognized definition of the suffix ''-mancy''), to include any spiritual, metaphysical, or pseudoscientific practice that is related to the Earth. In recent times the term has been applied to a wide range of other occult and fringe activities, including Earth mysteries and the introduction of ley lines and . Geomancy was one of the forms of divination throughout Africa and Europe in premodern times, but was considered a forbidden practice by Christians in medieval Europe.Johannes Hartlieb (Munich, 1456) ''The Book of All Forbidden Arts''; quoted in In other regions and cultures, geomancy practices include ''Sikidy'' and ''Ifá'' (found in Africa), I Ching and Feng shui (found in China), Ku ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Central America
Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually defined as consisting of seven countries: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama. Within Central America is the Mesoamerican biodiversity hotspot, which extends from southern Mexico to southeastern Panama. Due to the presence of several active geologic faults and the Central America Volcanic Arc, there is a high amount of seismic activity in the region, such as volcanic eruptions and earthquakes, which has resulted in death, injury, and property damage. Most of Central America falls under the Isthmo-Colombian cultural area. Before the Spanish expedition of Christopher Columbus' voyages to the Americas, hundreds of indigenous peoples made their homes in the area. From the year 1502 onwards, Spain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hematite
Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . It has the same crystal structure as corundum () and ilmenite (). With this it forms a complete solid solution at temperatures above . Hematite occurs naturally in black to steel or silver-gray, brown to reddish-brown, or red colors. It is mined as an important ore mineral of iron. It is electrically conductive. Hematite varieties include ''kidney ore'', ''martite'' ( pseudomorphs after magnetite), ''iron rose'' and ''specularite'' ( specular hematite). While these forms vary, they all have a rust-red streak. Hematite is not only harder than pure iron, but also much more brittle. The term ''kidney ore'' may be broadly used to describe botryoidal, mammillary, or reniform hematite. Maghemite is a polymorph of hematite (γ-) with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
