WHAT IS AN ELECTRICIAN?

An electrician is a tradesman specializing in electrical wiring of buildings and related equipment. Electricians may be employed in the installation of new electrical components or the maintenance and repair of existing electrical infrastructure.

Terminology
In the United States electricians are sometimes referred to as Inside Wireman as opposed to Outside Linemen who work on electric utility company distribution systems at higher voltages. "Electrician" is also used as the name of a role in stagecraft, where electricians are tasked primarily with hanging, focusing, and operating stage lighting. In this context, the Master Electrician is the show's chief electrician. Although theater electricians routinely perform electrical work on stage lighting instruments and equipment, they are not part of the electrical trade and have a different set of skills and qualifications from the electricians that work on building wiring. In the United Kingdom, and Australia "spark" or "sparkie" is slang term for an electrician.

Training and regulation of trade

In most countries, the job of an electrician is a regulated trade for safety reasons due to the many hazards of working with electricity, requiring testing, registration, or licensing. Licensing of electricians is controlled through government and/or professional societies.

United States
In the United States licensing requirements for construction work are controlled by local building officials. Typically, certain types of electrical work are only permitted to be performed by a Journeyman or Master electrician. The requirements for becoming a journeyman or master electrician, and the types of work they are permitted to do, vary between states; however, there are often interstate reciprocity agreements. Not all states offer a statewide journeyman or master electrician license. Before electricians are allowed to work without supervision, they are usually required to serve an apprenticeship lasting from 3 to 5 years under the general supervision of a Master Electrician and usually the direct supervision of a Journeyman Electrician. Schooling in electrical theory and electrical building codes is usually required to complete the apprenticeship program. A Journeyman electrician is a well rounded craftsman trained in all phases of electrical construction installation in various building styles and maintenance of equipment after installation. A Journeyman is usually permitted to perform all types of electrical work except design of electrical systems. A Master Electrician must first be a Journeyman and usually has a minimum of two years more experience and has to pass further testing. A Master Electrician is further trained in layout, estimation, and design of electrical installations. Certification usually requires experience and a passing score on a written test. The written test usually includes questions about the NFPA's National Electrical Code, and load calculations.

WHAT IS ELECTRICITY?

Electricity (from New Latin e-lectricus, "amber-like") is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena such as lightning and static electricity, but in addition, less familiar concepts such as the electromagnetic field and electromagnetic induction.

In general usage, the word 'electricity' is adequate to refer to a number of physical effects. However, in scientific usage, the term is vague, and these related, but distinct, concepts are better identified by more precise terms:

* Electric charge – a property of some subatomic particles, which determines their electromagnetic interactions. Electrically charged matter is influenced by, and produces, electromagnetic fields.

* Electric current – a movement or flow of electrically charged particles, typically measured in amperes.

* Electric field – an influence produced by an electric charge on other charges in its vicinity.

* Electric potential – the capacity of an electric field to do work, typically measured in volts.

* Electromagnetism – a fundamental interaction between the electric field and the presence and motion of electric charge.

Electricity has been studied since antiquity, though scientific advances were not forthcoming until the seventeenth and eighteenth centuries. It would not be until the late nineteenth century, however, that engineers were able to put electricity to industrial and residential use. This period witnessed a rapid expansion in the development of electrical technology. 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. The backbone of modern industrial society is, and for the foreseeable future can be expected to remain, the use of electrical power.

History of Electricity

Knowledge of electric discharge from electric fishes was first reported in 2750 BC by the ancient Egyptians, who referred to it as the "thunderer of the Nile". They were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians. Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by catfish and torpedo rays, and knew that such shocks could travel along conducting objects. Patients suffering from ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them. Similar observations were later reported by Al-Jahiz in medieval Egypt. That certain objects such as rods of amber could be rubbed with cat's fur and attract light objects like feathers was known to ancient cultures around the Mediterranean. Thales of Miletos made a series of observations on static electricity around 600 BC, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians in Mesopotamia (now Iraq) may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artefact was electrical in nature.

Electricity would remain little more than an intellectual curiosity for over two millennia until 1600, when the English physician 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, the Greek word for "amber") to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646. Further work was conducted by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay. In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. He observed a succession of sparks jumping from the key to the back of his hand, showing that lightning was indeed electrical in nature

In 1791 Luigi Galvani published his discovery of bioelectricity, demonstrating that electricity was the medium by which nerve cells passed signals to the muscles. Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used. André-Marie Ampère discovered the relationship between electricity and magnetism in 1820; Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827. While it had been the early 19th century that had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering. Through such people as Nikola Tesla, Thomas Edison, 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 Revolution.

Concepts - Electric charge

Electric charge is a property of certain subatomic particles, which gives rise to and interacts with, the electromagnetic force, one of the four fundamental forces of nature. Charge originates in the atom, in which its most familiar carriers are the electron and proton. It is a conserved quantity, that is, the net charge within an isolated system will always remain constant regardless of any changes taking place within that system. Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire. The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other.

The presence of charge gives rise to the electromagnetic force: charges exert a force on each other, an effect that was known, though not understood, in antiquity. A lightweight ball suspended from a string 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 also repel each other. However, if one ball is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb, who deduced that charge manifests itself in two opposing forms, leading to the well-known axiom: like-charged objects repel and opposite-charged objects attract.

The force acts on the charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb's law, which relates the force to the product of the charges and has an inverse-square relation to the distance between them. The electromagnetic force is very strong, second only in strength to the strong interaction,[20] but unlike that force it operates over all distances. In comparison with the much weaker gravitational force, the electromagnetic force pushing two electrons apart is 1042 times that of the gravitational attraction pulling them together.

The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. By convention, the charge carried by electrons is deemed negative, and that by protons positive, a custom that originated with the work of Benjamin Franklin. The amount of charge is usually given the symbol Q and expressed in coulombs; each electron carries the same charge of approximately -1.6022×10-19 coulomb. The proton has a charge that is equal and opposite, and thus +1.6022×10-19 coulomb. Charge is possessed not just by matter, but also by antimatter, each antiparticle bearing an equal and opposite charge to its corresponding particle.

Charge can be measured by a number of means, an early instrument being the gold-leaf electroscope, which although still in use for classroom demonstrations, has been superseded by the electronic electrometer

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. By historical convention, a positive current is defined as having the same direction of flow 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. If another definition is used—for example, "electron current"—it needs to be explicitly stated.

The process by which electric current passes through a material is termed electrical conduction, and its nature varies with that of the charged particles and the material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis, where ions (charged atoms) flow through liquids. While the particles themselves can move quite slowly, sometimes with a average drift velocity only fractions of a millimetre per second, the electric field that drives them itself propagates at close to the speed of light, enabling electrical signals to pass rapidly along wires. Current causes several observable effects, which historically were the means of recognising its presence. That water could be decomposed by the current from a voltaic pile was discovered by Nicholson and Carlisle in 1800, a process now known as electrolysis. Their work was greatly expanded upon by Michael Faraday in 1833. Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840. One of the most important discoveries relating to current was made accidentally by Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in a wire disturbing the needle of a magnetic compass. He had discovered electromagnetism, a fundamental interaction between electricity and magnetics.

In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how the current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative. If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes the form of a sinusoidal wave. Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance. These properties however can become important when circuitry is subjected to transients, such as when first energised.

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 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. Thus gravity is the dominant force at distance in the universe, despite being much the weaker.

An electric field generally varies in space, and its strength at any one point is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point. The conceptual charge, termed a 'test charge', must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of magnetic fields. As the electric field is defined in terms of force, and force is a vector, so it follows that an electric field is also a vector, having both magnitude and direction. Specifically, it is a vector field.

The study of electric fields created by stationary charges is called electrostatics. The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday, whose term 'lines of force' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves.

The principals of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between the charged parts. Air, for example, tends to arc at electric field strengths which exceed 30 kV per centimetre across small gaps. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre. The most visible natural occurrence of this is lightning, caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of a large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh. The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor, the sharp spike of which acts to encourage the lightning stroke to develop there, rather than to the building it serves to protect.

Electric potential

The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work. The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity. This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference, and is the energy required to move a unit charge between two specified points. An electric field has the special property that it is conservative, which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated. The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage. For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged – and unchargeable.

Electric potential is a scalar quantity, that is, it has only magnitude and not direction. It may be viewed as analogous to temperature: as there is a certain 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, or field strength, indicates the direction and magnitude of the driving force behind charge movement. Equally, electric potential may be seen as analogous to height: just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field. The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre, the vector direction of the field is the line of greatest gradient of potential.

Electromagnetism

Ørsted's discovery in 1821 that a magnetic field existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces, the two forces of nature then known. The force on the compass needle did not direct it to or away from the current-carrying wire, but acted at right angles to it. Ørsted's slightly obscure words were that "the electric conflict acts in a revolving manner." The force also depended on the direction of the current, for if the flow was reversed, then the force did too. Ørsted did not fully understand his discovery, but he observed the effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by Ampère, who discovered that two parallel current carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing current flowing in opposite directions are forced apart. The interaction is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere.

This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. Faraday's homopolar motor consisted of a permanent magnet sitting in a pool of mercury. A current was allowed to flow through a wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained. Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as electromagnetic induction, enabled him to state the principal, now known as Faraday's law of induction, that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. Exploitation of this discovery enabled him to invent the first electrical generator in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy. Faraday's disc was inefficient and of no use as a practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work.

Faraday's and Ampère's work showed that a time-varying magnetic field acted as a source of an electric field, and a time-varying electric field was a source of a magnetic field. Thus, when either field is changing in time, then a field of the other is necessarily induced. Such a phenomenon has the properties of a wave, and is naturally referred to as an electromagnetic wave. Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell discovered a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that such a wave would necessarily travel at the speed of light, and thus light itself was a form of electromagnetic radiation. Maxwell's Laws, which unify light, fields, and charge are one of the great milestones of theoretical physics.

Electric circuits

An electric circuit is an interconnection of electric components, usually to perform some useful task, with a return path to enable the charge to return to its source. The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics. Electronic circuits contain active components, usually semiconductors, and typically exhibit non-linear behavior, requiring complex analysis. The simplest electric components are those that are termed passive and linear: while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli. The resistor is perhaps the simplest of passive circuit elements: as its name suggests, it resists the flow of current through it, dissipating its energy as heat. Ohm's law is a basic law of circuit theory, stating that the current passing through a resistance is directly proportional to the potential difference across it. The ohm, the unit of resistance, was named in honour of Georg Ohm, and is symbolised by the Greek letter ?. 1 ? is the resistance that will produce a potential difference of one volt in response to a current of one amp.

The capacitor is a device capable of storing charge, and thereby storing electrical energy in the resulting field. Conceptually, it consists of two conducting plates separated by a thin insulating layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance. The unit of capacitance is the farad, named after Michael Faraday, and given the symbol F: one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current to flow as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit a steady state current to flow, but instead blocks it. The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current flowing through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality is termed the inductance. The unit of inductance is the henry, named after Joseph Henry, a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second. The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current to flow, but opposes the flow of a rapidly changing one.

Production and uses -

Generation

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. 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. 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 in bulk. Electrical energy 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. 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. The invention in the late nineteenth century of the transformer meant that electricity could be generated at centralised power stations, benefiting from economies of scale, and be transmitted across countries with increasing efficiency. 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. 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, a rate of growth that is now being experienced by emerging economies such as those of India or China. Historically, the growth rate for electricity demand has outstripped that for other forms of energy, such as coal. 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.

Uses

Electricity is an extremely flexible form of energy, and 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 burgeoning market for electrical lighting. The Joule heating effect employed in the light bulb also sees more direct use in electric heating. While this is versatile and controllable, it can be seen as wasteful, since most electrical generation has already required the production of heat at a power station. A number of countries, such as Denmark, have issued legislation restricting or banning the use of electric heating in new buildings. Electricity is however a highly practical energy source for refrigeration, with air conditioning representing a growing sector for electricity demand, the effects of which electricity utilities are increasingly obliged to accommodate. Electricity is used within telecommunications, and indeed the electrical telegraph, demonstrated commercially in 1837 by Cooke and Wheatstone, was one of its earliest applications. With the construction of first intercontinental, and then transatlantic, telegraph systems in the 1860s, electricity had enabled communications in minutes across the globe. Optical fibre and satellite communication technology have taken a share of the market for communications systems, but electricity can be expected to remain an essential part of the process. The effects of electromagnetism are most visibly employed in the electric motor, which provides a clean and efficient means of motive power. A stationary motor such as a winch is easily provided with a supply of power, but a motor that moves with its application, such as an electric vehicle, is obliged to either carry along a power source such as a battery, or by collecting current from a sliding contact such as a pantograph, placing restrictions on its range or performance. Electronic devices make use of the transistor, perhaps one of the most important inventions of the twentieth century,[63] and a fundamental building block of all modern circuitry. A modern integrated circuit may contain several billion miniaturised transistors in a region only a few centimetres square.

Electricity retailing

Electricity retailing is the final process in the delivery of electricity from generation to the consumer. The other main processes are transmission and distribution.

Beginnings
Electricity retailing began at the end of the 19th century when the bodies who generated electricity for their own use made supply available to third parties. In the beginning, electricity was primarily used for street lighting and trams. The general public were allowed to purchase electricity only after large scale electric companies were started. The provision of these services was generally the responsibility of electric companies or municipal authorities who either set up their own departments or contracted the services from private entrepreneurs. Residential, commercial and industrial use of electricity was confined, initially, to lighting but this changed dramatically with the development of electric motors, heaters and communication devices. The basic principle of supply has not changed much over time. The amount of energy used by the domestic consumer, and thus the amount charged for, is measured through an electricity meter that is usually placed near the input of a home to provide easy access to the meter reader. Customers are usually charged a monthly service fee and additional charges based on the electrical energy (in kWh) consumed by the household or business during the month. Commercial and industrial consumers normally have more complex pricing schemes. These require meters that measure the energy usage in time intervals (such as a half hour) to impose charges based on both the amount of energy consumed and the maximum rate of consumption, i.e. the maximum demand, which is measured in kVA.

Monopoly supply
The rapid growth in electric appliance usage in the early part of the 20th century contributed to an explosive growth in electrification around the world. The supply of electricity to homes, offices, shops, factories, farms, and mines became the responsibility of public utilities, which were either private organizations subject to monopoly regulation or public authorities owned by local, state or national bodies. In some countries a statutory or government-granted monopoly was created, which was controlled by legislation (for example Eskom in South Africa). Home electrical meters Home electrical meters Electricity retailing in the period from approximately 1890 to 1990 consisted of managing the connection, disconnection and billing of electricity consumers by the local monopoly supplier. In many utilities there was a marketing function which encouraged electricity usage when there was excess capacity to supply and encouraged conservation when supply was tight.

Creating a market
In 1990 there was a significant development in the way electricity was bought and sold. In many countries, the electricity market was deregulated to open up the supply of electricity to competition. In the United Kingdom the Electricity Supply Industry was radically reformed to establish competition. This trend continued in other countries (see New Zealand Electricity Market and deregulation) and the role of electricity retailing changed from what was essentially an administrative function within an integrated utility to become a risk management function within a competitive electricity market. Electricity retailers now provide fixed prices for electricity to their customers and manage the risk involved in purchasing electricity from spot markets or electricity pools. This development has not been without casualties. The most notable example of poor risk management (coupled with poor market regulation) was the 2001 California electricity crisis, when Pacific Gas and Electric and Southern California Edison were driven into bankruptcy by having to purchase electricity at high spot prices and sell at low fixed rates. Customers may choose from a number of competing suppliers. They may also opt to pay more for "green" power, i.e. electricity sourced from renewable energy generation such as wind power or solar power. An electricity provider is often known as "the electric company" or "the power company".

Rates
The rates charged for electricity vary between countries, regions and states. The reason for the variation is primarily regulation and the way it is generated. For example, some states in the US have large hydroelectric generation facilities that are largely subsidized and relatively efficient, and rates are as low as $0.06 per kWh, as in Idaho. In other states, such as California, which has to import electricity from neighboring states, the rates can be as high as $0.38 per kWh during peak hours for high-use residential customers that pay based on time of use . As of 2006 (May), the average rate for electricity in the US was approximately $0.106 per kWh .

ELECTRICIAN ORANGE COUNTY, ELECTRICIANS IN ORANGE COUNTY, ELECTRICAL CONTRACTOR ORANGE COUNTY, COMMERCIAL ELECTRICIANL, INDUSTRIAL ELECTRICIAN, RESIDENTIAL ELECTRICIAN, Anaheim, 92801, 92802, 92803, 92804, 92805, 92806, 92807, 92808, 92809, 92812, 92814, 92815, 92816, 92817, 92825, 92850, 92899, Brea, 92821, 92822, 92823, Buena Park, 90620, 90621, 90622, 90623, 90624, Costa Mesa, 92626, 92627, 92628, Cypress, 90630, Fountain Valley, 92708, 92728, Fullerton, 92831, 92832, 92833, 92834, 92835, 92836, 92837, 92838, Garden Grove, 92840, 92841, 92842, 92843, 92844, 92845, 92846, Huntington Beach 92605, 92615, 92646, 92647, 92648, 92649, Irvine, 92602, 92603, 92604, 92606, 92612, 92614, 92616, 92618, 92619, 92620, 92623, 92650, 92697, 92709, 92710, La Habra, 90631, 90632, 90633, La Palma, 90623, Los Alamitos, 90720, 90721, Orange, 92856, 92857, 92859, 92861, 92862, 92863, 92864, 92865, 92866, 92867, 92868, 92869, Placentia 92870, 92871, Santa Ana, 92701, 92702, 92703, 92704, 92705, 92706, 92707, 92708, 92711, 92712, 92725, 92728, 92735, 92799, Seal Beach, 90740, Stanton, 90680, Tusin, 92780, 92781, 92782, Villa Park, 92861, 92867, Westminister, 92683, 92684, 92685, Yorba Linda, 92885, 92886, 92887,Aliso Viejo, 92653, 92656, 92698, Dana Point, 92624, 92629,Laguna Beach, 92607, 92637, 92651, 92652, 92653, 92654, 92656, 92677, 92698, Laguna Hills, 92637, 92653, 92654, 92656, Laguna Niguel, 92607, 92677, Laguna Woods, 92653, 92654, Lake Forest, 92609, 92630, Mission Viejo, 92675, 92690, 92691, 92692, 92694, Newport Beach, 92657, 92658, 92659, 92660, 92661, 92662, 92663, Rancho Santa Margarita, 92688, San Clemente, 92672, 92673, 92674, San Juan Capistrano, 92675, 92690, 92691, 92692, 92693, 92694, Ladera Ra,nch, 92694, Coto De Caza 92679 Anaheim Hills, 92807, 92808, 92809, 92817, Dove Canyon, 92679, Coto De Caza, 92679, Newport Coast, 92657, Corona Del Mar, 92625, El Modena, Las Flores, Midway City, Orange Park Acres, Rossmoor, Silverado Canyon, Sunset Beach, Surfside, Trabuco Canyon, Talega, Tustin Foothills , OC

ABOUT ORANGE COUNTY CALIFORNIA:

Orange County is a county in Southern California, United States. Its county seat is Santa Ana. According to the 2000 Census, its population was 2,846,289, making it the second most populous county in the state of California, and the fifth most populous in the United States. The state of California estimates its population as of 2007 to be 3,098,121 people, dropping its rank to third, behind San Diego County. Thirty-four incorporated cities are located in Orange County; the newest is Aliso Viejo.

Unlike many other large centers of population in the United States, Orange County uses its county name as its source of identification whereas other places in the country are identified by the large city that is closest to them. This is because there is no defined center to Orange County like there is in other areas which have one distinct large city. Five Orange County cities have populations exceeding 170,000 while no cities in the county have populations surpassing 360,000. Seven of these cities are among the 200 largest cities in the United States.

Orange County is also famous as a tourist destination, as the county is home to such attractions as Disneyland and Knott's Berry Farm, as well as sandy beaches for swimming and surfing, yacht harbors for sailing and pleasure boating, and extensive area devoted to parks and open space for golf, tennis, hiking, kayaking, cycling, skateboarding, and other outdoor recreation. It is at the center of Southern California's Tech Coast, with Irvine being the primary business hub.

The average price of a home in Orange County is $541,000. Orange County is the home of a vast number of major industries and service organizations. As an integral part of the second largest market in America, this highly diversified region has become a Mecca for talented individuals in virtually every field imaginable. Indeed the colorful pageant of human history continues to unfold here; for perhaps in no other place on earth is there an environment more conducive to innovative thinking, creativity and growth than this exciting, sun bathed valley stretching between the mountains and the sea in Orange County.

Orange County was Created March 11 1889, from part of Los Angeles County, and, according to tradition, so named because of the flourishing orange culture. Orange, however, was and is a commonplace name in the United States, used originally in honor of the Prince of Orange, son-in-law of King George II of England.

Incorporated: March 11, 1889 Legislative Districts: * Congressional: 38th-40th, 42nd & 43 * California Senate: 31st-33rd, 35th & 37 * California Assembly: 58th, 64th, 67th, 69th, 72nd & 74 County Seat: Santa Ana County Information: Robert E. Thomas Hall of Administration 10 Civic Center Plaza, 3rd Floor, Santa Ana 92701 Telephone: (714)834-2345 Fax: (714)834-3098 County Government Website: http://www.oc.ca.gov