Basic Electrostatics System
ES-9080B
26
®
3B.4: V Measured, C Variable, Q Constant
1.
Figure 3.4 shows the equipment set up. The Variable Capacitor is connected to the
electrometer and the electrometer is grounded to earth (through the COM port on the voltage
source). The voltage source will be used to only momentarily charge the capacitor.
2.
With the plate separation at 2 mm, charge the plates by momentarily connecting them
across the voltage source, set at 30 V. Adjust the scale sensitivity of the electrometer so
that the initially charged plates represent a meter reading of about 1/5 scale.
3.
Increase the plate separation and note the electrometer’s readings at various separations.
How does the potential vary with capacitance?
NOTE:
An alternative method is to charge one of the spheres and then transfer some charge
to the capacitor. The charge, however, will not be as high.
Procedure 3C: Dielectric Coefficients
The dielectric coefficient
is the dimensionless factor by which the capacitance increases
(relative to the value of capacitance before the dielectric) when a dielectric is inserted
between the plates. It is a fundamental property of the dielectric material and is independent
of the size or shape of the capacitor. Table 3.1 lists the dielectric coefficients of some
common materials.
Figure 3.4: Demonstration Setup
