Is It an Electroscope or Electrometer? 

Terminology

There are two methods used to distinguish electroscopes and electrometers. In neither case is the distinction perfectly clear or completely satisfactory. 

The first approach employs the term electroscope for any device used to make a qualitative measurement of an electrostatic charge and to use the term electrometer for a device used to make quantitative measurements. If a scale is used, the device would therefore be considered an electrometer. 

The second method, employed here, is to use the term electroscope for a device that only requires an initial charge to function. The change in this initial charge is measured by observing he movement of a leaf or fiber. No auxiliary potential is necessary. An electrometer, on the other hand, requires the maintenance of a fixed auxiliary potential (e.g., between two pairs of quadrants). The change in the collected charge being measured causes the movement of a vane, needle or fiber within the electric field created by the auxiliary potential. 

Some of the instruments in the collection that have been described as electrometers could just as easily, and perhaps more appropriately, have been described as electroscopes.

Advantages of Electrometers

1.  Electrometers are usually more sensitive than electroscopes

2.  It is fairly easy to change the sensitivity of an electrometer.

Advantages of Electroscopes

1. Electroscopes are unaffected by changes in temperature and humidity

2. They do not require a stable source of power

3. They are simple to set up and use.

4. They are portable and relatively resistant to vibration >

5. They are relatively inexpensive

In general, electroscopes were preferred  by chemists while physicists preferred to use electrometers.  Nevertheless, despite the greater sophistication of the electrometer, the electroscope was often the instrument of choice.

 

Electroscopes                   Museum Directory

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