Electricity is the set of physical phenomena associated with the presence and motion of

matter that has a property of electric charge. Electricity is related to magnetism, both
being part of the phenomenon of electromagnetism, as described by Maxwell's equations.
Various common phenomena are related to electricity, including lightning, static
electricity, electric heating, electric discharges and many others.

Lightning is one of the most dramatic effects of electricity.

The presence of an electric charge, which can be either positive or negative, produces
an electric field. The movement of electric charges is an electric current and produces
a magnetic field.
When a charge is placed in a location with a non-zero electric field, a force will act on it.
The magnitude of this force is given by Coulomb's law. If the charge moves, the electric
field would be doing work on the electric charge. Thus we can speak of electric
potential at a certain point in space, which is equal to the work done by an external agent
in carrying a unit of positive charge from an arbitrarily chosen reference point to that
point without any acceleration and is typically measured in volts.
Electricity is at the heart of many modern technologies, being used for:

 electric power where electric current is used to energise equipment;

Electrical phenomena have been studied since antiquity, though progress in theoretical
understanding remained slow until the seventeenth and eighteenth centuries. The
theory of electromagnetism was developed in the 19th century, and by the end of that
century electricity was being put to industrial and residential use by electrical engineers.
The rapid expansion in electrical technology at this time transformed industry and
society, becoming a driving force for the Second Industrial Revolution. Electricity's
extraordinary versatility means it can be put to an almost limitless set of applications
which include transport, heating, lighting, communications, and computation. Electrical power
is now the backbone of modern industrial society.[1]
Production and uses
Generation and transmission
Main article: Electricity generation

See also: Electric power transmission and Mains electricity

Early 20th-century alternator made in Budapest, Hungary, in the power generating hall of a hydroelectric station

In the 6th century BC, the Greek philosopher Thales of Miletus experimented with amber rods
and these experiments were the first studies into the production of electrical energy. While this
method, now known as the triboelectric effect, can lift light objects and generate sparks, it is
extremely inefficient.[64] 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.[64] 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 heat 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.
[65] 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.[66][67]
Wind power is of increasing importance in many countries

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.[66] 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,[68] a rate of growth that is now being experienced by emerging
economies such as those of India or China.[69][70] Historically, the growth rate for electricity
demand has outstripped that for other forms of energy.[71]:16
Environmental concerns with electricity generation have led to an increased focus on generation
from renewable sources, in particular from wind and solar. While debate can be expected to
continue over the environmental impact of different means of electricity production, its final
form is relatively clean.[71]:89
Applications

The light bulb, an early application of electricity, operates by Joule heating: the passage
of current through resistance generating heat

Electricity is a very convenient way to transfer energy, and it has been adapted to a huge, and
growing, number of uses.[72] 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.[73] Public utilities were set up in many cities
targeting the burgeoning market for electrical lighting. In the late 20th century and in modern
times, the trend has started to flow in the direction of deregulation in the electrical power sector.
[74]
The resistive Joule heating effect employed in filament light bulbs 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.[75] A number
of countries, such as Denmark, have issued legislation restricting or banning the use of resistive
electric heating in new buildings.[76] Electricity is however still a highly practical energy source
for heating and refrigeration,[77] with air conditioning/heat pumps representing a growing sector
for electricity demand for heating and cooling, the effects of which electricity utilities are
increasingly obliged to accommodate.[78]
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 transcontinental, and then transatlantic, telegraph systems in the 1860s,
electricity had enabled communications in minutes across the globe. Optical fibre and satellite
communication 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 to collect current
from a sliding contact such as a pantograph. Electrically powered vehicles are used in public
transportation, such as electric buses and trains,[79] and an increasing number of battery-
powered electric cars in private ownership.
Electronic devices make use of the transistor, perhaps one of the most important inventions of
the twentieth century,[80] 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.[81]