®
ES-9080B
012-07227G
Basic Electrostatics System
7
Variable Capacitor (ES-9079)
The PASCO experimental variable
capacitor consists of two conductivel
plates, 20 cm in diameter, which can be
adjusted to various separations. The
movable plate is mounted on a calibrated
slide which gives the plate separation
directly in centimeters. Binding posts on
each plate are provided for electrical
connection. Three plastic spacers are
attached to the fixed plate so that when the
movable plate is made to touch these
spacers, the plate separation is 1 mm.
A low-capacitance cable to connect the
plates to the electrometer is included. Keep
the leads of the cable separated as much as
possible to minimize their capacitance.
It is very important that the plates of the
capacitor remain parallel. It is possible that
through mishandling, they will cease to be parallel, and adjustments must be made. On the
back side of the movable plate are two screws for adjusting the plate horizontally and
vertically.
Keep the plate supports clean to prevent charge leakage from the plates.
Charge Producers and Proof Plane (ES-9057B)
The Charge Producers and the Proof Plane are
electrostatic components for use with the PASCO
Electrostatic System. The charge producers are used to
generate charges by contact. The proof plane is used to
measure charge density on a charged surface.
The charge producers consist of two wands, one with
dark material and one with white material attached to a
conductive disk, as shown in Figure 4. If the dark and
white surfaces are briskly rubbed together, the white
surface acquires a positive charge, and the dark surface
acquires a negative charge.
Here are some guidelines in the proper use and care of the charge producers that are
important to remember:
• If a zero charge is desirable, discharge the charge producers by touching the conductive disk
to ground. To be sure the disk is fully discharged, gently breathe on the non-conductive
neck. The moisture from your breath will help remove any stray charge.
Figure 3: Variable Capacitor
Movable
plate
Fixed
plate
Binding
post
Figure 4: Charge Producers
Handle
Non-conductive neck
Non-conductive neck
Conductive knob
