Czech Gold-Leaf Electroscope (early 1900s)

This is a gold leaf electroscope intended for qualitative demonstrations of electrostatic phenomena.

Unfortunately, it has no markings on it that would identify the manufacturer. However my understanding is that it came from a university in the Czech Republic. As such, it is referred to as a Czech electroscope (even though it might have been manufactured elsewhere).

The body is glass. The condenser (Volta) plate, conduction rod and collar are brass. The two gold leaves attached to the bottom of the vertical conductor (support) rod are in good condition. 

As a rule, it was desirable to employ electrically conductive glass for the body of an electroscope. This minimized the possibility that a static charge would accumulate on the surface of the glass - such a charge could affect the movement of the leaves.

Quoting Kolbe (1888): "It is important to choose a glass which conducts well, in order to get rid of the disturbing influence of the glass sides. Moreover the glass vessel must be so spacious that the leaves, even when charged, are at a distance of 0.5 to 1 centim. from the glass. If the glass is not a good conductor, the vessel should be so wide that the leaves (when horizontal) are at a distance of 2 to 2.5 centim. from the glass."

Kolbe notes that electroscopes made of insulating glass "often fail in dry air; for such glass acts like a condenser, and only discharges slowly. . . Among 184 kinds [of glass] which I tried I only found 19 which I could use, and only three of these were very good."

 

It might be worth pointing out the long tubular glass insulator that surrounds the conduction rod - for this application, you would not want conductive glass. By having it extend the entire length of the conducting rod, you minimize any leakage current across its surface.

In general, a device known as an electrophorus would be used to transfer a charge to the condenser (the horizontal plate on the top).  For an explanation of how an electroscope can be charged and how an electrophorus works, click here. 

There is nothing particularly remarkable about this particular electroscope, but it is well made and in excellent condition.

Size: ca. 12" high, 4.5" diameter (maximum)

References:

Kolbe, B. Electroscope for Purposes of Demonstration. Zet. fur Phys. und Chem. Unterricht. Vol. IV. 1888.

Electroscopes               Museum Directory

Last updated: 07/25/07
Copyright 1999, Oak Ridge Associated Universities