012-07227A
Basic Electrostatics System
1
Introduction
Due to problems of technique and apparatus, demonstrations of electrostatic phenomenon have
traditionally been limited to the simplest experiments using the most elementary equipment.
Moreover, the traditional demonstrations usually gave qualitative rather than quantitative results.
PASCO has attempted to remedy this by designing the complete ES-9079 Basic Electrostatics
system. This guide will give the instructor enough of a step-by-step explanation to master
demonstration techniques. The range of demonstrations in this guide more than covers the material
usually presented in an undergraduate unit on electrostatics.
There are several essential principles of electrostatic demonstrations that should be remembered.
• Read the first section of this manual regarding theory and use of the electrostatic accessories.
• Equipment orientations - Arrange the apparatus to be used so that it is sufficiently separated and
neatly arranged to insure that the students can clearly see the set-up. Each demonstration
includes a diagram of suggested equipment set-up. A preferred set-up would also use a
computer with a Science Workshop interface to display the readings from the Electrometer (ES-
9078) in a computer screen that all can easily see. (You can use an analog display, for example,
to show the deflections of the needle; or a digits display to show the voltage.) If a computer is
not available, set the demonstration electrometer upright to allow the meter to be seen more
easily. Always consider how the equipment arrangement may affect charge distributions. For
example, a misplaced power supply can easily change the charge distribution on a nearby
sphere. Finally, always stand behind the demonstration table to avoid obstructing anyone’s
view.
• Earth grounds - Although it is not always strictly necessary, the demonstrator should be
connected to an earth ground. Stray charges on the demonstrator can cripple an experiment.
Also keep the electrometer grounded unless specific instructions are given to the contrary.
• Avoid unnecessary movement - If the demonstrator walks around or waves his/her arms
excessively, charge can build up in clothing and affect the results.
• Humidity - The PASCO demonstration electrometer has been designed to minimize the effects
of humidity. However, a particularly humid day can cause charges to leak off various apparatus,
radically changing the charge distribution. To help minimize leakage, keep all equipment free of
dust and oil (e.g. from fingerprints). On the other hand, a particularly dry day can cause charge
to easily build up in any moving object, including people. Minimize all movement when
demonstrating on a very dry day.
• Practice - Nothing can ruin the instructive value of a demonstration more than failure due to a
demonstrator unfamiliar with the equipment and procedure.
Before presenting a series of electrostatic demonstrations, the student (and of course, the instructor)
should be made aware of the following: