Electricity

ELECTRICITY:

What:

Electricity is from the New Latin ēlectricus, "amber-like", from the Greek electron meaning amber. It is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include lightning and static electricity. Electricity travels through what's called a circuit, going around and through objects until it gets back to where it started.You can't store electricity. Once you generate it, you have to use it right away or it disappears. In the Pacific Northwest, a lot of electricity is generated by the dams you see on the Columbia River and other local rivers. At these dams, water flows through turbines and spins those turbines, which generates electricity.

Here is a picture of lightning:



Picture found at:

http://www.google.com/search?ie=UTF-8&oe=UTF-8&sourceid=navclient&gfns=1&q=google

In general usage, the word "electricity" refers to a number of physical effects. In scientific usage, however, the term is vague, and these related, but distinct, concepts are better identified by more precise terms. Electrical phenomena have been studied since antiquity, though advances in the science were not made until the seventeenth and eighteenth centuries. Practical applications for electricity however remained few, and it would not be until the late nineteenth century that [|engineers] were able to put it to industrial and residential use. The rapid expansion in electrical technology at this time transformed industry and society. Electricity's extraordinary versatility as a source of energy means it can be put to an almost limitless set of applications which include [|transport] [|heating], [|lighting], [|communications], and [|computation]. Electrical power is the backbone of modern industrial society, and is expected to remain so for the foreseeable future.[|[1]] Long before any knowledge of electricity existed people were aware of shocks from [|electric fish]. aware of shocks from [|electric fish]. [|Ancient Egyptian] texts dating from [|2750 BC] referred to these fish as the "Thunderer of the [|Nile]", and described them as the "protectors" of all other fish.

Who and When:

People think Benjamin Franklin discovered electricity with his famous kite-flying experiments in 1752. T

hat isn’t the whole story. Electricity was not “discovered” all at once. Electricity is an action—not really a thing—so different forms of electricity had been known in nature for a long time. Lightning and static electricity were two forms. Mr. Edison & His Light In 1879, Thomas Edison focused on inventing a practical light bulb, one that would last a long time before burning out. The challenge was finding a strong material to be used as the filament, the small wire inside the bulb that conducts the electricity. Finally, Edison used ordinary cotton thread that had been Image courtesy of NOAA Photo Library soaked in carbon. The filament Image courtesy of U.S. Library of Congress did not burn—instead, it Thomas Edison in his lab in 1901. In the early years, electricity became associated with light. After all, electricity lights up the sky during a thunderstorm. Likewise, static electricity creates tiny, fiery sparks. People wanted a cheap and safe way to light their homes, and scientists thought electricity could do it.While it was the early 19th century that had seen progress in electrical science, in the late 19th century, we would see the greatest progress in [|electrical engineering]. Through such people as [|Nikola Tesla], [|Thomas Edison], [|Ottó Bláthy], [|Ányos Jedlik], [|Sir Charles Parsons],[|George Westinghouse], [|Ernst Werner von Siemens], [|Alexander Graham Bell] and [|Lord Kelvin], electricity was turned from a scientific curiosity into an essential tool for modern life, becoming a driving force for the [|Second Industrial Revolutio]

Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist [|William Gilbert] made a careful study of electricity and magnetism, distinguishing the [|lodestone] effect from static electricity produced by rubbing amber.] He coined the [|New Latin] word //electricus// ("of amber" or "like amber", from //ήλεκτρον// [//elektron//], the Greek word for "amber") to refer to the property of attracting small objects after being rubbed.

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 particles; most commonly these are electrons, but any charge in motion constitutes a current. By historical convention, a positive current is defined as having the same direction of fl

ow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called [|conventional current]. The motion of negatively charged electrons around an [|electric circuit], one of the most familiar forms of current, is thus deemed positive in the //opposite// direction to that of the electrons. However, depending on the conditions, an electric current can consist of a flow of [|charged particles] in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation.

Electric Field:

The concept of 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 always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero.

Links:

http://www.wikipedia.org http://www.clarkpublicutilities.com/community/homeworkHelp/whatIsElectricity http://www.google.com.hk/search?q=history+of+electricity&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

Production and uses:
Thales' experiments with amber rods were the first studies into the production of electrical energy. While this method, now known as the [|triboelectric effect], is capable of lifting light objects and even generating sparks, it is extremely inefficient.[|[][|50][|]] 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 energy chemically and make it available on demand in the form of electrical energy.[|[][|50][|]] The battery is a versatile and very common power source which is ideally suited to many applications, but its energy storage is finite, and once discharged it must be disposed of or recharged. For large electrical demands electrical energy must be generated and transmitted continuously over conductive transmission lines. Electrical power is usually generated by electro-mechanical [|generators] driven by [|steam] produced from [|fossil fuel] combustion, or the heat released from [|nuclear reactions]; or from other sources such as [|kinetic energy] extracted from wind or flowing water. The modern [|steam turbine] invented by [|Sir Charles Parsons] in 1884 today generates about 80 percent of the [|electric power] in the world using a variety of hea

t sources. Such generators bear no resemblance to Faraday's homopolar disc generator of 1831, but they still rely on his electromagnetic principle that a conductor linking a changing magnetic field induces a potential difference across its ends.[|[][|51][|]] 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.[|[][|52][|]][|[][|53][|]] Since electrical energy cannot easily be stored in quantities large enough to meet demands on a national scale, at all times exactly as much must be produced as is required.[|[][|52][|]] This requires [|electricity utilities] to make careful predictions of their electrical loads, and maintain constant co-ordination with their power stations. A certain amount of generation must always be held in [|reserve] to cushion an electrical grid against inevitable disturbances and losses. Demand for electricity grows with great rapidity as a nation modernises and its economy develops. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century,[|[][|54][|]] a rate of growth that is now being experienced by emerging economies such as those of India or China.[|[][|55][|]][|[][|56][|]] Historically, the growth rate for electricity demand has outstripped that for other forms of energy.[|[][|57][|]] [|Environmental concerns with electricity generation] have led to an increased focus on generation from [|renewable sources], in particular from [|wind] and [|hydropower]. While debate can be expected to continue over the environmental impact of different means of electricity production, its final form is relatively clean.[|[][|58][|]]

Electricity and the natural world:
Main article: [|Electric shock] 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.[|[][|68][|]] 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.[|[][|69][|]] If the current is sufficiently high, it will cause muscle contraction, [|fibrillation] of the heart, and [|tissue burns].[|[][|68][|]] The lack of any visible sign that a conductor is electrified makes electricity a particular hazard. The pain caused by an electric shock can be intense, leading electricity at times to be employed as a method of [|torture]. Death caused by an electric shock is referred to as [|electrocution]. Electrocution is still the means of [|judicial execution] in some jurisdictions, though its use has become rarer in recent times.[|[][|70][|]]

Cultural perception
In the 19th and early 20th century, electricity was not part of the everyday life of many people, even in the industrialised [|Western world]. The [|popular culture] of the time accordingly often depicts it as a mysterious, quasi-magical force that can slay the living, revive the dead or otherwise bend the laws of nature.[|[][|76][|]] This attitude began with the 1771 experiments of [|Luigi Galvani] in which the legs of dead frogs were shown to twitch on application of [|animal electricity]. "Revitalization" or resuscitation of apparently dead or drowned persons was reported in the medical literature shortly after Galvani's work. These results were known to [|Mary Shelley] when she authored //[|Frankenstein]// (1819), although she does not name the method of revitalization of the monster. The revitalization of monsters with electricity later became a stock theme in horror films. As the public familiarity with electricity as the lifeblood of the [|Second Industrial Revolution] grew, its w

ielders were more often cast in a positive light,[|[][|77][|]] such as the workers who "finger death at their gloves' end as they piece and repiece the living wires" in [|Rudyard Kipling]'s 1907 poem //[|Sons of Martha]//.[|[][|77][|]] Electrically powered vehicles of every sort featured large in adventure stories such as those of [|Jules Verne] or the //[|Tom Swift]// books.[|[][|77][|]] The masters of electricity, whether fictional or real—including scientists such as [|Thomas Edison], [|Charles Steinmetz] or [|Nikola Tesla]—were popularly conceived of as having wizard-like powers.[|[][|77][|]] With electricity ceasing to be a novelty and becoming a necessity of everyday life in the later half of the 20th century, it required particular attention by popular culture only when it //stops// flowing,[|[][|77][|]] an event that usually signals disaster.[|[][|77][|]] The people who //keep// it flowing, such as the nameless hero of [|Jimmy Webb]’s song "[|Wichita Lineman]" (1968),[|[][|77][|]] are still often cast as heroic.

Time Line:


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|| Thales, a Greek, found that when amber was rubbed with silk it attracted feathers and other light objects. He had discovered static electricity. The Greek word for amber is ëelectron', from which we get ëelectricity' and ëelectronics'. 1600: William Gilbert invented the term electricity William Gilbert, scientist and physician to Queen Elizabeth I, invented the term electricity (from the Greek word for amber, elecktra). He was the first person to describe the earth's magnetic field and to realise that there is a relationship between magnetism and electricity. 1705: Francis Hauksbee invented Neon Light Francis Hauksbee created electrical effects by putting some mercury into a glass globe, pumping out the air and then spinning it. When he did this in the dark, and then rubbed the globe with his bare hand, it glowed. (He didn't realise it, but he had invented the neon light!) 1752: Franklin proved that lightning is a form of electricity Benjamin Franklin, famous U.S. politician, flew a kite with a metal tip into a thunderstorm to prove that lightning is a form of electricity. He was very lucky he wasn't killed. Don't try this at home! 1700s: The Wimshurst machine was invented The Wimshurst machine was invented. It is used to produce static electricity easily and reliably. Two parallel plates are rotated in opposite directions, which produces a charge around the edges of the plates. The charge is collected by a system of combs.†Voltages as high as 50,000 volts can be produced, depending on humidity and other conditions, as well as sparks up to four inches long. 1780: Luigi Galvani's dead frog's legs An Italian called Luigi Galvani discovered that when he touched a dead frog's leg with a knife, it twitched violently. Alessandro Volta later showed that this was because electricity is created when moisture (from the frog) comes between two different types of metal (the steel knife and a tin plate). 1800: Volta's Pile
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 * ^  ||   || The timeline ||
 * Main events ||
 * 600BC: Static electricity

Volta created the first simple battery. He used pure silver and zinc discs, sandwiched between muslin damped in a salt solution, developed from Galvani's earlier experiments with a frog's leg. 1800: Sir Humphry Davy discovered Electrolysis Sir Humphry Davy discovered that when he passed an electric current through some substances they decomposed. This process later became known as electrolysis. Davy's experiments with electrolysis led to the discovery of a number of elements, including magnesium, calcium, strontium and barium. 1820: Hans Christian Oersted discovered magnetic fields caused by electricity Hans Christian Oersted of Denmark found that when electricity flows through a wire, it produces a magnetic field that affects the needle of a nearby compass. 1821: Michael Faraday's discovery that led to the invention of electric motors Michael Faraday discovered that when a magnet is moved inside a coil of copper wire, a tiny electric current flows through the wire. This discovery later led to the invention of electric motors. 1821: Thomas Johann Seebeck discovered Thermo-electricity Thomas Johann Seebeck found that when the junction of certain metals is heated, electricity flows ñ thermo-electricity. 1826: André Ampère explained the electro-dynamic theory André Ampère published his theories about electricity and magnetism. He was the first person to explain the electro-dynamic theory. The unit of electric current was named after Ampère. 1827: Georg Ohm published his complete mathematical theory of electricity German college teacher Georg Ohm published his complete mathematical theory of electricity. The unit of electrical resistance was later named after him. 1829: Joseph Henry's discovery into electromagnetism Joseph Henry showed that a wire wrapped in coils produces a greater electromagnetism than a straight one. 1830: Joseph Henry discovered the principles of the dynamo Joseph Henry discovered the principles of the dynamo. 1831: Michael Faraday demonstrated electromagnetic induction Michael Faraday demonstrated electromagnetic induction by passing a magnet through a coil of wire. 1831: The First Telegraph Machine Charles Wheatstone and William Fothergill Cooke created the first telegraph machine. 1834: Charles Wheatstone measured the velocity of electricity Charles Wheatstone used a revolving mirror and four miles of wire to measure the velocity of electricity. 1838: Samuel Morse invented Morse Code At an exhibition in New York, Samuel Morse demonstrated sending 10 words a minute by his new

telegraph machine. He used a system of dots and dashes, which later became standard throughout the world, known as Morse code. 1870s: Thomas Edison built a DC electric generator Thomas Edison built a DC (direct current) electric generator in America. He later provided all of New York's electricity. 1876: Alexander Graham Bell invented of the telephone Alexander Graham Bell, inventor of the telephone, used electricity to transmit speech for the first time. 1878: Joseph Swan demonstrated the first Electric Light Joseph Swan, a British scientist, demonstrated the first electric light with a carbon filament lamp. A few months later, Thomas Edison made the same discovery in America. 1880s: Nikola Tesla developed an AC motor Nikola Tesla developed an AC (alternating current) motor and a system of AC power generation. Edison saw Tesla's system as a threat to his DC supply and spread stories that it wasn't not safe. But, after Tesla's system was used to power 100,000 electric lights at Chicago's World Fair in 1893, AC became the established power supply in the USA. 1880s: Nikola Tesla invented the Telsa Coil Nikola Tesla used the ëTesla coil' to step up ordinary household current to produce extremely high frequency current. Tesla used this high frequency current to develop some of the first neon and fluorescent lights. 1881: The first public electricity supply The first public electricity supply was generated in Godalming, Surrey using a waterwheel at a nearby mill. 1883: Magnus Volks built the first electric railway The first electric railway opened on Brighton seafront, built by electrical engineer Magnus Volks. The Volks Railway, built just for pleasure rides, is one mile long and still runs during the summer season. 1884: Charles Parsons built his first turbine Charles Parsons built his first turbine. This is a type of engine which is operated by jets of high pressure gases. This type of engine was later developed to drive the propellers of boats, including the Titanic. 1886: Heinrich Hertz produced and detected electric waves Heinrich Hertz produced and detected electric waves in the atmosphere. 1890: Turbine driven generators

Turbine driven generators were introduced to produce electricity. 1892: Hendrik Lorentz published his electron theory. Dutch physicist Hendrik Lorentz published his electron theory. 1895: The first electric hand drill The first electric hand drill became available, invented by Wilhelm Fein. 1895: Discovery of X-rays The German phsyicist Wilhelm Roentgen discovered invisible rays that made a distant screen glow and passed through objects. These were X-rays. 1896: Nikola Tesla's hydroelectric power generators Nikola Tesla's hydroelectric power generators at Niagara Falls came into operation. Within a few years, Tesla's generators at Niagara Falls were supplying electricity to New York City for the elevated railways, the subways and even the lights on Broadway. 1897: Marconi sends radio message Guglielmo Marconi sends a radio message from The Isle of Wight to Poole (20 miles away). Later he sends a message across the Atlantic. 1905: Albert Einstein and photovoltaic cells Albert Einstein demonstrated that light energy could be used to produce electricity ñ the idea behind photovoltaic cells was born. 1918-19: Washing machines and refrigerators Electric washing machines and refrigerators first became available. 1926: First National Grid was introduced Electricity Supply Act ñ the first National Grid was introduced. 1930-40s: Hydro-electric power stations Hydro-electric power stations were built in Scotland and Wales, but the majority of electricity generation was from burning coal. 1930-40s: Electrical household appliances introduced Mains powered radios, vacuum cleaners, irons and fridges were becoming part of every household. 1936: John Logie Baird pioneered the television. 1956: First large-scale nuclear power station The world's first large-scale nuclear power station opened at Calder Hall in Cumbria. The reactors were a prototype of the Magnox gas cooled reactor. 1960s: Advanced gas cooled reactors: The UK decided to develop advanced gas cooled reactors to succeed the earlier Magnox stations. Around the same time, France and the USA decided to adopt water cooled reactor technology. 1994: The UK's first pressurised water reactor The UK's first pressurised water reactor (PWR) was opened at Sizewell B in Suffolk. It had taken 7 years to build, after the largest ever public enquiry in the UK. No further nuclear reactors have been built in the UK since then. 2000: The world's first commercial wave power station The world's first commercial wave power station on the Scottish island of Islay began to generate electricity. Devices are placed on the shoreline or out at sea that use wave motion to compress air to drive a turbine or hydraulic pumps. The station is called LIMPET (Land-Installed Marine-Powered Energy Transformer) and can provide enough electricity for about 400 homes. ||  ||
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