Electroscope
electrometer - electroscope - charge and voltage measurement
What it shows:
The electroscope, or electrometer, is an instrument that measures
electric charge or voltage by means of repulsive electrostatic force.
How it works:
We have essentially discontinued use of the "gold-leaf" electroscope
in favor of the Braun type shown below.
The Braun electroscope has a light needle pivoted on a horizontal axis.
The needle is balanced in a vertical position. The action is similar
to that of the "gold-leaf" type in that, when support rod and needle
are charged similarly, electrostatic forces cause the needle to rotate
to a new equilibrium position which depends on the amount of charge.
The needle deflection is calibrated directly in volts.
1
Setting it up:
The large electroscope does not require any visual aids (it was made large
for that reason). The movement of the small electroscope needle may well
be made visible to the class by video projection. Use back lighting by
placing a photographic light box (slide-viewer) behind the electroscope -
this will give a high-contrast silhouette image.
Comments:
The electroscope may be an old instrument, but its elegant simplicity makes
it a must for electrostatic experiments. Rating ****
1 One is 1500V maximum deflection and the other is 3500V; the other two are uncalibrated.