Alexander Volta invented an electrophorus model, in which the two pendulums are reached by threading two thin metallic wires, suspended by two small, mobile, silver rings, in two straws (straw electrometer).
This new structure allowed him to obtain:
- Less electricity dispersion, thanks to the insulating action of the straws;
- a better approach of the two elements sensitive to repulsion;
- a more regular behaviour with respect to the small sphere of elder pith, as well as the gold leaves.
Alexander Volta predisposed, then inside the electroscope, a gradated quadrant in order to measure the spread and therefore the amount of electricity. This way, the electroscope literally became an electrometer. For a better reading, on the gradated scale, of the spread of the straws, bottles were needed.
It is an electrometer realised by means of a single, mobile, pivoted pendulum in its extreme superior, to a small rod of conducting material.
The pendulum is made up of a fine rigid conductor with a small sphere of light material (cork or elder pith) on the end of it.
If the device is loaded, the pendulum, by a repulsive action between the charge of the same sign, rises, rotating around the pivot, by angle, the size of depends on the charge present on the electrometer.
Many trips depart from Brunate: just 2 km way is S. Maurizio, where in 1927 the Voltaic Lighthouse (a 29 m. octagonal tower), visible by most of Lake Como, and from which opens a very vast panorama of the Alps and Mt. Rosa.
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