Question

Explain the construction of a gold leaf electroscope.

Answer 1

It consists of a vertical metal rod, usually brass, from the end of which hang two parallel strips of thin flexible gold leaf. A disk or ball terminal is attached to the top of the rod, where the charge to be tested is applied. To protect the gold leaves from drafts of air they are enclosed in a glass bottle, usually open at the bottom and mounted over a conductive base. Often there are grounded metal plates or foil strips in the bottle flanking the gold leaves on either side. These are a safety measure; if an excessive charge is applied to the delicate gold leaves, they will touch the grounding plates and discharge before tearing. They also capture charge leaking through the air that could accumulate on the glass walls, and increase the sensitivity of the instrument. In precision instruments the inside of the bottle was occasionally evacuated, to prevent the charge on the terminal from leaking off through ionization of the air.