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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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Electricity
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1992-09-03
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47 lines
Electricity is classed as all phenomena
caused by electric charge, whether static
or in motion. Electric charge is caused by
an excess or deficit of electrons in the
charged substance, and an electric current
by the movement of electrons around a
circuit. Some items are electrical
conducyors, such as metals,which allow the
passage of electricity to pass through them,
or insulators, such as rubber, which are
extremely poor conductors. Substances with
relatively poor conductivities that can be
improved by the addition of heat or light are
known as semiconductors.
Electricity generated on a commercial scale
was available from the early 1880s and used
for electric motors driving all kinds of
machinery, and for lighting, first by carbon
arc, but later by incandescent filaments
(first of carbon and then of tungsten),
enclosed in glass bulbs partially filled
with inert gas under vacuum. Light is also
produced by passing electricity through a gas
or metal vapour or a fluorescent lamp. Other
practical applications include telephone,
radio, television, X-ray machines, and many
other applications in electronics.
Electricity is generated at power stations at
a voltage of about 25,000 volts, which is not
a suitable voltage for long- distance
transmission. For minimal power loss,
transmission must take place at very high
voltage (400,000 volts or more). The
generated voltage is therefore increased by a
transformer.
UK electricity generation in th UK was split
into four companies in 1990 in preparation
for nationalization. The nuclear power
stations remain in the hands of the state
through Nuclear Electric (accounting for 20%
of electricity generated); National Power
(50%) and PowerGen (30%) generate electricity
from fossil-fuel and renewable sources.
Subject by: Robert Small