012–07227A
Basic Electrostatics System
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Demonstration 1: Faraday Ice Pail and Charge Production
EQUIPMENT NEEDED:
—Electrometer
—Faraday Ice Pail
—Charge Producers
—Test Leads
—Earth Ground Connection
—Proof Plane (optional)
Suggestions for Introducing the Experiment
Start by showing that the electrometer is directly measuring potential difference by
connecting a battery to it and measuring its voltage. You can explain that when
using the ice pail, you will be only indirectly measuring charge, knowing that the
amount of charge is proportional to the voltage. The readings will be in volts, not in
coulombs. Change the polarity of the leads to show how the meter needle deflects
in the opposite direction. Explain how this can tell us the type of charge in the ice pail.
Equipment Set Up
Introduction
The purpose of this demonstration is to investigate the relation between the charge
induced on the ice pail by a charged object placed in the pail, and the charge of the
object. This demonstration is also useful for investigating the nature of charging an
object by contact as compared to charging it by induction, and to demonstrate the
conservation of charge.
Before beginning any experiment using the ice pail, the pail must be momentarily
grounded. When the ice pail is connected to the electrometer, and the electrometer is
connected to an earth-ground, simply press the ZERO button whenever you need to
discharge both the pail and the electrometer. While conducting an experiment, it is
electrometer
grounded
shield
Figure 1.1 Demonstration Setup
earth ground
shield
pail