Immagini

DESCRIPTION

Exhibit 782 is a Ramsden electrostatic machine invented around the end of the 18th century by Jesse Ramsden (1735 - 1800). A complete Ramsden machine is illustrated in fig. 1 from ref-1.

The machine consists of a large glass disk DD' that rotates around its horizontal axis fixed in a sturdy wood support in the form of an inverted horseshoe. The wheel is rotated by a hand crank. The disk is charged positive being rubbed by leather cushions which transfer their negative charge directly to ground. The horizontal metal brushes BB' placed diametrically opposed at the outer rim of the rotating glass disk are charged negatively by induction, polarize the air molecules which release positive ions toward the brushes and negative ions toward the glass disk which requires work done to keep the positive charge and the three cylindrical conductors connected to the brushes become charged positively due to the captured positive ions. For further details see ref.1.

BIBLIOGRAPHY

• [1] Leandro Segalin,"Fisica Sperimentale Ad uso dell'istituto Tecnico Industriale", G.B. Paravia &C. 1933. Pag.192.
• [2] Oreste Murani,"Trattato Elementare di Fisica", Volume secondo, Ottica ed Elettricità, Ulrico Hoepli, Milano. 1931. § 245, pag.381.

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