The electroscope is provided with a charging rod C. In a dry atmosphere sulphur or amber is an early perfect insulator, and hence if the air in the interior of the box is kept dry by calcium chloride, the electroscope will hold its charge for a long time.
A third great use of the electroscope is therefore to detect electric conductivity either in the air or in any other body.
Well as of discharging a charged electroscope (Com.
It was then found that when the end plates of Volta's pile were connected to an electroscope the leaves diverged either with positive or negative electricity.
On the plate of a gold-leaf electroscope place a metal canister having a loose lid.
For this purpose the following apparatus should be provided: - (i) two small metal tea-trays and some clean dry tumblers, the latter preferably varnished with shellac varnish made with alcohol free from water; (2) two sheets of ebonite rather larger than the tea-trays; (3) a rod of sealing-wax or ebonite and a glass tube, also some pieces of silk and flannel; (4) a few small gilt pith balls suspended by dry silk threads; (5) a gold-leaf electroscope, and, if possible, a simple form of quadrant electrometer (see Electroscope and Electrometer); (6) some brass balls mounted on the ends of ebonite penholders, and a few tin canisters.
Another type of sensitive electroscope is one devised by C. T.
If, without removing the electrified body, the plate or knob of the electroscope is touched, the leaves collapse.
As already mentioned, Faraday remedied this defect by coating the inside of the glass vessel in which the gold-leaves were suspended to form an electroscope with tinfoil (see fig.
Volta made use of such an electroscope in his celebrated experiments (1790-1800) to prove that metals placed in contact with one another are brought to different potentials, in other words to prove the existence of so-called contact electricity.