Faraday, Michael
Faraday, Michael (1791-1867), British physicist and chemist who made
major advances in the study of magnetism, electricity, and the chemical effect
of a current.
He started his working life as a bookbinder, but in 1813
became laboratory assistant to Humphry Davy at the Royal Institution, where
he eventually became director. Working as an analytical chemist, he discovered
benzene in 1825 and prepared the first known compounds of carbon and chlorine.
He also investigated the composition of alloy steels and optical glasses.
But his greatest achievements were in electromagnetism. In 1821 he constructed
a simple form of electric motor, applying Hans Christian Oersted's discovery
that electric currents produce a magnetic effect. After much research Faraday
showed that the converse was also true--that a magnetic field can induce an
electric current.
In 1831 he published his laws of electromagnetic
induction and put them to practical use in the dynamo and the transformer, two
inventions that are fundamental to large-scale electricity generation and supply.
His laws of electrolysis, published in 1834 and named after him,
described the changes caused by electric current passing through liquids. Other
discoveries included diamagnetism (a weak magnetic effect present in all materials),
and the rotation of light waves by strong magnetic fields. Arguably one
of the most outstanding experimental scientists, he refused a knighthood and
the Presidency of the Royal Society because he feared that such honours would
undermine his integrity and his intellectual freedom.
Electromagnetic
induction, the production of an electrical potential difference (p.d.) or voltage
across a conductor situated in a changing magnetic field. Faraday was able
to describe this behaviour mathematically: he found that the size of the p.d.
produced is proportional to the rate of change of the magnetic flux. This applies
whether the flux itself changes in strength or the conductor is moved through
it.
Electromagnetic induction fundamentally underlies the operation
of generators, electric motors, and most other electrical machines, along with
the complementary law ascribed to Andre-Marie Ampere, who in 1820 demonstrated
that if a conductor carrying an electrical current is placed in a magnetic field
at right angles to current flow, the conductor will experience a force on
it at right angles to both field and current.
Foale, William (Life Span Unknown)
Very little is known about this engineer, but
he is recorded in the Trinity House archives as being the designer of the North
Low light at Killingholme established in 1852.
Foster, John (1786-1846)
This engineer/architect was associated with another architect
named Cockerell. He was appointed as the Chief Architect/Surveyor for the Corporation
of Liverpool in 1824. He took over this position from his father who
died the same year. He is recorded as being the designer for the Rock Lighthouse
on the Mersey in 1830.
Fresnel, Augustine Jean (1788-1827)
French physicist and civil engineer. He took up the study
of polarized light in 1814 and postulated that light moved in a wave-like motion,
which had already been suggested by, among others, Christiaan Huygens and Thomas
Young.
They, however, assumed the waves to be longitudinal, while
by 1821 Fresnel was sure that they vibrated transversely to the direction
of propagation, and he used this to explain successfully the phenomenon of double
refraction. He invented a large lens, made up of a series of concentric rings,
for lighthouses and searchlights (Fresnel lens).
He is accredited with the developement and invention of dioptric and
catadioptric principles with glass.
His optical invention was originally
based upon the refracting qualities of glass. Like an object viewed in water
it looks distorted. This is the easiest way to understand refraction or the
bending properties.
His original discovery relating to lenses appears
to have been an accident, when he noticed how the sun's rays were concentrated
or magnified as the beams passed through bull's eye panes of glass used in domestic
windows. He also noticed how it singed the curtains.
Experiments
were then carried out with prism shaped sections of glass laid along side
a bull's eye pane of glass. It was then noticed that the sun's rays were redirected
back through the central piece of glass, if these prisms were set at specific
angles.
When first tested with a 20 candle power (candelas) oil
lamp, it was recorded that the beam was increased by 500 times.
The
first Fresnel optic was installed in the Corduan lighthouse in France on the 23rd
July 1823.
The first Fresnel optic used in a Scottish light was in
October 1825 by Alan Stevenson, the Engineer-in-Chief for the Commissioners of
the Northern Lights.
The first Fresnel optic was not introduced to
the Trinity House lights until 1836.
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