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Franklin, Benjamin

electrical electricity charge using

(1706–90) US statesman: classic experimenter and theorist on static electricity.

Franklin had an unusually wide range of careers: he was successful as a printer, publisher, journalist, politician, diplomat and physicist. Trained as a printer and working in New England and for nearly 2 years in London (UK), Franklin found he also had talents as a journalist; when he was 27 he published Poor Richard’s Almanac . In this, he ‘filled all the little spaces that occurred between the remarkable days in the calendar with proverbial sentences’ which he concocted. Most are trite platitudes of the ‘honesty is the best policy’ kind, but some show the sly irony of his journalism (of which the best-known sample is probably his advice to young men to take older mistresses, ‘because they are so grateful ’). The almanac made him both famous and prosperous and, by franchises in printing shops and other businesses in which he provided a third of the capital and took a third of the profit, he made himself wealthy.

When he was nearly 40 he became interested in electricity, which at that time provided only amusing tricks, but at least the dry air of Philadelphia made these more reproducible than in damper climates. Franklin’s experiments and ideas turned electrical tricks into a science, made him the best-known scientist of his day and, perhaps for the first time, showed that what we would now call pure research could have important practical uses.

Franklin proposed that electrical effects resulted from the transfer or movement of an electrical ‘fluid’ made of particles of electricity (we would now call them electrons) that can permeate materials (even metals) and which repel each other but are attracted by the particles of ordinary matter. A charged body on this theory is one that has either lost or gained electrical fluid, and is in a state he called positive or negative (or plus or minus). Linked with this ‘one fluid’ idea was the principle or law of conservation of charge: the charge lost by one body must be gained by others so that plus and minus charges appear, or neutralize one another, in equal amounts and simultaneously. Franklin’s logic had its defects, but it was a major advance; and he continued to experiment, and worked on insulation and grounding. He examined the glow that surrounds electrified bodies in the dark, and it may have been this which caused a friend to show that a grounded metallic point could quietly ‘draw off’ the charge from a nearby charged object. This led Franklin to his idea that it should be possible to prove whether clouds are electrified (as others had suggested) and also to propose that ‘would not these pointed rods probably draw the electrical fire silently out of a cloud before it came nigh enough to strike, and thereby secure us from that most sudden and terrible mischief?’ He planned in 1750 an experiment using a metal rod passing into a sentry box mounted on the steeple of a new church; but delay in building it led him to try using a kite instead, and he found that the wet string did indeed conduct electricity from the thundercloud and charge a large capacitor. The electrical nature of such storms was proved, lightning conductors became widely used, Franklin became famous and others trying such experiments were killed. Benjamin Franklin aged about 70, portrayed shortly before the War of Independence. He is wearing the bifocal spectacles he invented, and a cap enhances his homespun image. Engraving by A de Saint-Aubin.

He was in London for most of the years 1757–75 representing the American colonies and trying to prevent the rising conflict. When, despite his efforts, war began, he was active in support of the revolution and was one of the five men who drafted the Declaration of Independence in 1776. In the same year he went as ambassador to France and, largely through his fame as a scientist and his popularity, secured an alliance in 1778. Afterwards he continued to be active in American politics; despite being an Anglophile, a womanizer and a tippler, he was increasingly seen as the virtuous, homespun, true American sage. His work in physics amused him but was always directed to practical use; he devised the Franklin stove with an efficient underfloor air-supply for heating, invented and used bifocal spectacles, used a flume for testing ships by using models, and his work on the Gulf Stream was a pioneering study in oceanography. By having ship’s captains record its temperature at various depths and its velocity, he mapped the Gulf Stream and studied its effects on weather.

In the 1780s he was present at the first ascents by hydrogen balloons made by at Versailles and enthused over the possibility of studying the atmosphere and of aerial travel; he foresaw aerial warfare. His book, Experiments and Observations on Electricity made at Philadelphia in America (1751) not only founded a new science, but had the incidental result of interesting in science, with momentous results for chemistry.

Franklin, Benjamin (1706-1790) [next] [back] Franklin, Benjamin - Overview, Personal Life, Career Details, Social and Economic Impact, Chronology: Benjamin Franklin

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