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The first electroscope was a pivoted needle (called the versorium), invented by British physician William Gilbert around 1600. [1] [2] The pith-ball electroscope and the gold-leaf electroscope are two classical types of electroscope [2] that are still used in physics education to demonstrate the principles of electrostatics.
English: Diagram showing how a pith-ball electroscope works. The molecules (yellow ovals) that make up the pith ball (A) consist of positive charges (atomic nuclei) and negative charges (electrons) close together. Bringing a charged object (B) near the pith ball causes these charges to separate
Canton is now mainly remembered for his work in electrostatics, [2] particularly the invention of the pith ball electroscope, and his studies in atmospheric electricity. [8] He is honoured with a blue plaque at the site of his old school in his hometown of Stroud. [9]
A gold-leaf electroscope (E), a sensitive detector of electric charge, is attached by a wire to the outside of the pail. When the charged ball is lowered into the pail without touching it, the electroscope registers a charge, indicating that the ball induces charge in the metal container by electrostatic induction. An opposite charge is induced ...
Torsion is used to give a measurement more sensitive than repulsion of gold leaves or cork-balls. It consists of a glass cylinder with a glass tube on top. In the axes of the tube is a glass thread, the lower end of this holds a bar of gum lac, with a gilt pith ball at each extremity.
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The collector, consisting of a series of metal points, was added to the machine by Benjamin Wilson about 1746, and in 1762, John Canton of England (also the inventor of the first pith-ball electroscope in 1754 [38]) improved the efficiency of electric machines by sprinkling an amalgam of tin over the surface of the rubber. [11]
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