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China,[h] officially the People's Republic of China (PRC),[i] is a country in East Asia. With a population exceeding 1.4 billion, it is the world's second-most populous country after India. China spans the equivalent of five time zones and borders fourteen countries by land.[j] With an area of nearly 9.6 million square kilometers (3,700,000 sq ...
Taiwan,[II][k] officially the Republic of China (ROC),[I][l] is a country[27] in East Asia.[o] It is located at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the northeast, and the Philippines to the south. The territories controlled by the ...
China's was the only major world economy to experience GDP growth in 2020, when its GDP increased by 2.3%. [101] However, it posted one of its worst economic performances in decades because of COVID-19 in 2022. [102] In 2023, IMF predicted China to continue being one of the fastest growing major economies. [103]
the free encyclopedia that anyone can edit. "The Day Before the Revolution" is a science fiction short story by American writer Ursula K. Le Guin (pictured). First published in Galaxy in August 1974, it was republished in Le Guin's The Wind's Twelve Quarters (1975). Set in her fictional Hainish universe, the story has strong connections to her ...
- History
- Concepts
- Production, Storage and Uses
- Electricity and The Natural World
- Cultural Perception
- References
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Long before any knowledge of electricity existed, people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BCE described them as the "protectors" of all other fish. Electric fish were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians. Several ancient writers, such as Pliny th...
Electric charge
The presence of charge gives rise to an electrostatic force: charges exert a force on each other, an effect that was known, though not understood, in antiquity.: 457 A lightweight ball suspended by a fine thread can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod als...
Electric current
The movement of electric charge is known as an electric current, the intensity of which is usually measured in amperes. Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current. Electric current can flow through some things, electrical conductors, but will not flow through an electrical insulator. By historical convention, a positive current is defined as having the same direction of flow as any positive charge it c...
Electric field
The concept of the electric field was introduced by Michael Faraday. An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses, and like it, extends towards infinity and shows an inverse square relationship with distance.However, there is an important difference. Gravity...
Generation and transmission
In the 6th century BC the Greek philosopher Thales of Miletus experimented with amber rods: these were the first studies into the production of electricity. While this method, now known as the triboelectric effect, can lift light objects and generate sparks, it is extremely inefficient. It was not until the invention of the voltaic pile in the eighteenth century that a viable source of electricity became available. The voltaic pile, and its modern descendant, the electrical battery, store ene...
Transmission and storage
The invention in the late nineteenth century of the transformer meant that electrical power could be transmitted more efficiently at a higher voltage but lower current. Efficient electrical transmission meant in turn that electricity could be generated at centralised power stations, where it benefited from economies of scale, and then be despatched relatively long distances to where it was needed. Normally, demand of electricity must match the supply, as storage of electricity is difficult. A...
Applications
Electricity is a very convenient way to transfer energy, and it has been adapted to a huge, and growing, number of uses. The invention of a practical incandescent light bulb in the 1870s led to lighting becoming one of the first publicly available applications of electrical power. Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories.Public utilities were set up in many cities targeting the...
Physiological effects
A voltage applied to a human body causes an electric current through the tissues, and although the relationship is non-linear, the greater the voltage, the greater the current. The threshold for perception varies with the supply frequency and with the path of the current, but is about 0.1 mA to 1 mA for mains-frequency electricity, though a current as low as a microamp can be detected as an electrovibration effect under certain conditions. If the current is sufficiently high, it will cause mu...
Electrical phenomena in nature
Electricity is not a human invention, and may be observed in several forms in nature, notably lightning. Many interactions familiar at the macroscopic level, such as touch, friction or chemical bonding, are due to interactions between electric fields on the atomic scale. The Earth's magnetic field is due to the natural dynamo of circulating currents in the planet's core. Certain crystals, such as quartz, or even sugar, generate a potential difference across their faces when pressed. This phen...
It is said that in the 1850s, British politician William Gladstone asked the scientist Michael Faraday why electricity was valuable. Faraday answered, "One day sir, you may tax it."However, according to Snopes.com "the anecdote should be considered apocryphal because it isn't mentioned in any accounts by Faraday or his contemporaries (letters, news...
Benjamin, Park (1898), A history of electricity: (The intellectual rise in electricity) from antiquity to the days of Benjamin Franklin, New York: J. Wiley & SonsHammond, Percy (1981), "Electromagnetism for Engineers", Nature, 168 (4262), Pergamon: 4–5, Bibcode:1951Natur.168....4G, doi:10.1038/168004b0, ISBN 0-08-022104-1, S2CID 27576009Morely, A.; Hughes, E. (1994), Principles of Electricity (5th ed.), Longman, ISBN 0-582-22874-3Nahvi, Mahmood; Joseph, Edminister (1965), Electric Circuits, McGraw-Hill, ISBN 978-0071422413Basic Concepts of Electricity chapter from Lessons In Electric Circuits Vol 1 DC book and series.Xi Jinping (/ˈʃiː dʒɪnˈpɪŋ/, or often /ˈʒiː/; Chinese: 习近平; pinyin: Xí Jìnpíng, pronounced [ɕǐ tɕîn.pʰǐŋ];[a] born 15 June 1953) is a Chinese politician who has been the general secretary of the Chinese Communist Party (CCP) and chairman of the Central Military Commission (CMC), and thus the paramount leader of ...
ISO 3166-1 ( Codes for the representation of names of countries and their subdivisions – Part 1: Country codes) is a standard defining codes for the names of countries, dependent territories, and special areas of geographical interest. It is the first part of the ISO 3166 standard published by the International Organization for Standardization .
