®
ES-9080B
012-07227G
Basic Electrostatics System
27
The ideal procedure to measure
would be to simply slip a piece of dielectric material
between a set of charged capacitor plates and then note the changes in potential. However,
sliding a dielectric between the plates of the capacitor when they are too close together can
generate a significant static charge that will alter the measurements. Hence, it is best to
proceed as follows:
NOTE:
Depending on the model of parallel plate capacitor you have, there may be only one
plate that is movable. If your model allows both plates to be moved, choose one to keep fixed
and the other to be the movable one.
1.
Connect the electrometer across the plates of the capacitor and set the separation between
the plates to about 3 mm.
2.
Raise the side of the set up nearest the movable plate by setting a block about 3 cm high
below it, as shown in Figure 3.5.
3.
Use the voltage source to momentarily touch the plates and charge them to about 4/5 full
scale. Record the voltage reading of the electrometer,
V
i
.
4.
Carefully increase the separation of the plates until it is enough to insert the dielectric
without forcing it. It should be enough so that you can simply lean the dielectric sheet
against the stationary plate. Make sure the dielectric you are using is free of residual
charge before inserting it.
Figure 3.5: Demonstration Setup
Block
