Basic Electrostatics System
012–07227A
12
3. Try rubbing the blue material with a proof plane. Measure the magnitude and
polarity of the charges produced.
4. Construct a list of materials such that if a material lower in the list is rubbed with
a material higher in the list, the higher material is always positive.
Demonstration 2: Charge Distribution
EQUIPMENT NEEDED:
—Electrometer
—Faraday Ice Pail
—Electrostatic Voltage Source (ES-9077)
—Proof Planes
—13 cm Conductive Spheres (2)
—Test Leads
—Earth Ground Connection - Patch cord
Equipment Set Up
* An earth ground for the system is obtained through the DC voltage source wall-mount power supply.
Introduction
The purpose of this demonstration is to investigate the way charge is distributed
over a surface, by measuring variations of charge density. A charged surface will be
sampled with a proof plane. The proof plane will then be inserted in the Faraday Ice
Pail to measure the charge. By sampling different sections of the surface, the
relative charge density can be observed. For example, you may find that the amount
of charge on two equal sized regions on the surface of a conductor may differ in
magnitude or even in sign. This occurs for non-uniform charge distribution. Or you
pail
charged
sphere
sampling
sphere
electrometer, shield
and VDC source
share common
ground
Figure 2.1 Demonstration Setup
DC voltage source*
electrometer
power cord
earth ground
ground VDC source to
earth or to shield