Benjamin Franklin was born in 1706, and was fascinated in his youth by electrical
phenomena. In 1732 he founded with his collaborators the Library Company of
Philadelphia with the support of the Penn family, and achieved a new insight into
electrical science with his definition of a ‘single electric fire’. This is equivalent to
the free-electron concept, and implies the principle of the conservation of charge.
In 1750 he showed that a needle brought near to a charged conductor caused
a spark, but when further away discharged the conductor silently (a mechanism today
known as a glow corona). Franklin wrote that: ‘this power of points may be of some
use to mankind’. Foremost in his mind was to achieve protection against lightning,
and in the famous Philadelphia Experiment (performed under Franklin’s direction by
d’Alibard in France in 1752) point discharges were used to prove the electrification
of the thundercloud and to identify correctly the direction of the field formed by
the cloud charges [1]. The public effect of these successes was great, and they were
regarded as the most important work since Newton.
Franklin, in fact, had envisaged from his laboratory tests two complementary
concepts for the function of a lightning rod:
Benjamin Franklin was born in 1706, and was fascinated in his youth by electricalphenomena. In 1732 he founded with his collaborators the Library Company ofPhiladelphia with the support of the Penn family, and achieved a new insight intoelectrical science with his definition of a ‘single electric fire’. This is equivalent tothe free-electron concept, and implies the principle of the conservation of charge.In 1750 he showed that a needle brought near to a charged conductor causeda spark, but when further away discharged the conductor silently (a mechanism todayknown as a glow corona). Franklin wrote that: ‘this power of points may be of someuse to mankind’. Foremost in his mind was to achieve protection against lightning,and in the famous Philadelphia Experiment (performed under Franklin’s direction byd’Alibard in France in 1752) point discharges were used to prove the electrificationof the thundercloud and to identify correctly the direction of the field formed bythe cloud charges [1]. The public effect of these successes was great, and they wereregarded as the most important work since Newton.Franklin, in fact, had envisaged from his laboratory tests two complementaryconcepts for the function of a lightning rod:
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