Electricity

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Electricity (from New Latin ēlectricus, "amberlike") is a general term for a variety of phenomena resulting from the presence and flow of electric charge. This includes many well-known physics phenomena such as lightning, electromagnetic fields and electric currents, and is put to use in Industry applications such as electronics and electric power. These related, but distinct, concepts are better identified by more precise terms:

Electric field — an effect produced by an electrically charged object that exerts a force on other charged objects in its vicinity.
Electric potential — the capacity of an electric field to do work, typically measured in volts (V).
Electric current — a movement or flow of electrically charged particles, typically measured in amperes (A).
Electrical energy — the energy made available by the flow of electric charge through an electrical conductor.
Electric power — the rate at which electric energy is converted to or from another energy form, such as light, heat, or mechanical energy.
Electric charge — a connection conserved property of some subatomic particles, which determines their electromagnetic interactions. Electrically charged matter is influenced by, and produces, electromagnetic fields.
Electromagnetism — a fundamental interaction

History of electricity Electrostatics produced by rubbing objects against fur was known to the ancient ancient Greece, Phoenicians, Parthians and Mesopotamians. Some propose that the Parthians and Mesopotamians may have had some knowledge of electroplating, based on the discovery of the Baghdad Battery, which resembles a galvanic cell, although this is disputed by many scholars.

In 1600 the English scientist William Gilbert first used the New Latin word electricus ("of amber" or "like amber", from ηλεκτρον , the Greek word for "amber") to refer to the property of attracting small objects after being rubbed. This soon gave rise to the English words "electric" and "electricity", in Sir Thomas Browne's Pseudodoxia Epidemica of 1646.

Further work was conducted by Otto von Guericke, Robert Boyle, Stephen Gray (scientist) and C. F. du Fay. In the 18th century, Benjamin Franklin conducted extensive research in electricity. He had theories on the relationship between lightning and static electricity, including his famous kite-flying experiment,which was a key attached to a wet string and kite. During a lightning storm a small spark struck his finger showing that lightning is electricity. This experiment was proved false on an episode of mythbusters on the episode entitled "Franklin's Kite" where it was shown that the electricity carried down the string would have been enough to kill him. It sparked the interest of later scientists whose work provided the basis for modern electrical technology. Most notably these include Luigi Galvani (1737–1798), Alessandro Volta (1745-1827), Michael Faraday (1791–1867), André-Marie Ampère (1775–1836), and Georg Ohm (1789-1854).

The late 19th and early 20th century produced such giants of electrical engineering as Nikola Tesla, Antonio Meucci, Thomas Edison, George Westinghouse, Werner von Siemens, Charles Steinmetz, Alexander Graham Bell and William Thomson, 1st Baron Kelvin.

Electric potential The Potential difference between two points is defined as the Mechanical work done (against electrical forces) per unit of charge in moving a positive point charge slowly between two points. If one of the points is taken to be a reference point with zero potential, then the electric potential at any point can be defined in terms of the work done per unit charge in moving a positive point charge from that reference point to the point at which the potential is to be determined. For isolated charges, the reference point is usually taken to be infinity. The potential is measured in volts. (1 volt = 1 joule/coulomb) The electric potential is analogous to temperature: there is a different temperature at every point in space, and the temperature gradient indicates the direction and magnitude of the driving force behind heat flow. Similarly, there is an electric potential at every point in space, and its gradient indicates the direction and magnitude of the driving force behind charge movement.

Electric current

An electric current is a flow of electric charge, and its intensity is measured in amperes. Examples of electric currents include metallic conduction, where electrons flow through a Electrical conductor such as a metal wire, and electrolysis, where ions (charged atoms) flow through liquids. The particles themselves often move quite slowly, while the electric field that drives them propagates at close to the speed of light. See electrical conduction for more information.

Devices that use charge flow principles in materials are called electronics.

A direct current (DC) is a unidirectional flow, while an alternating current (AC) reverses direction repeatedly. The time average of an alternating current is zero, but its energy capability (root mean square value) is not zero.

Ohm's law is an important relationship describing the behaviour of electric currents, relating them to voltage.

For historical reasons, electric Current (electricity) is said to flow from the most positive part of a circuit to the most negative part. The electric current thus defined is called conventional current. It is now known that, 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. If another definition is used - for example, "electron current" - it should be explicitly stated.

Electric field The concept of electric fields was introduced by Michael Faraday. The electrical field force acts between two charges, in the same way that the gravitational force acts between two masses. However, the electric field is a little bit different. Newton's law of universal gravitation depends on the masses of two bodies, whereas electric force depends on the electric charges of two bodies. While gravity can only pull masses together, the electric force can be an attractive or repulsive force. If both charges are of same sign (e.g. both positive), there will be a repulsive force between the two. If the charges are opposite, there will be an attractive force between the two bodies. The magnitude of the force varies inversely with the square of the distance between the two bodies, and is also proportional to the product of the unsigned magnitudes of the two charges.

Electric charge Electric charge is a property of certain subatomic particles (e.g., electrons and protons) which interacts with electromagnetic fields and causes attractive and repulsive forces between them.Electric charge is a fundamental conserved property of matter and can be precisely quantified. It couples to the electromagnetic field, one of the four fundamental forces of nature.

In this sense, the phrase "quantity of electricity" is used interchangeably with the phrases "electric charge" and "quantity of charge". There is fundamentally only one type of electric charge, and only one variable is needed to keep track of the amount of charge.One Kind of Charge The amount of charge may be positive or negative. Through experimentation, we find that like-charged objects repel and opposite-charged objects attract one another. The magnitude of the force of attraction or repulsion is given by Coulomb's law.

See also

Electrical engineering
Electricity generation
Electricity distribution
Electricity meter
Electrical phenomena
Electrostatics

Safety

Electric shock
High voltage

Electrical phenomena in nature

Matter: — since atoms and molecules are held together by electric forces.
Lightning: electrical discharges in the atmosphere.
The Earth's magnetic field — created by electric currents circulating in the planet's core.
Sometimes due to solar flares, a phenomenon known as a voltage spike can be created.
Piezoelectricity: the ability of certain crystals to generate a voltage in response to applied Stress (physics).
triboelectric effect: electric charge taken on by contact or friction between two different materials.
Bioelectromagnetism: electrical phenomena within Organism; Many animals are sensitive to electric fields, some (e.g., sharks) more than others (e.g., people). Most also generate their own electric fields.

Gymnotiformes, such as the electric eel, deliberately generate strong fields to detect or stun their prey.
Neurons in the nervous system transmit information by electrical impulses known as action potentials.

References

External links

Energy and Electricity Information
Tyndall: Faraday as Discovery: Identity of Electricities
US Energy Department Statistics
Read Congressional Research Service (CRS) Reports regarding Electricity
Answers to several question of curious kids about electricity
Illustrated view of how an American home's electrical system works
How to save on your electricity bills
Electricity around the world
A Comprehensive Collection of Franklin’s Electrical Works: The Electrical Writings of Benjamin Franklin, Created and Collected by Robert A. Morse (2004)
Understanding Electricity and some Electronics in 10 minutes (Steve Rose, Maui)
Electricity Misconceptions
Electricity and Magnetism