PASCO ES-9080A User Manual
Instruction Manual
Basic Electrostatics System
ES-9080A
012-07227G
*012-07227*
Basic Electrostatics System 012-07227G ES-9080A
®
Table of Contents
Equipment List.............................................................................................. 3
Introduction................................................................................................... 4
Equipment Description..........................................................................5 - 10
Electrometer...................................................................................................................................5
Electrostatics Voltage Source ........................................................................................................6
Variable Capacitor .........................................................................................................................7
Charge Producers and Proof Plane.................................................................................................7
Faraday Ice Pail..............................................................................................................................9
Conductive Spheres......................................................................................................................10
Conductive Shapes.......................................................................................................................10
Electrometer Operation and Setup Requirements ..................................... 11
Suggested Demonstrations.................................................................13 - 34
Demonstration 1: Faraday Ice Pail and Charge Production................................................. 13 - 16
Demonstration 2: Charge Distribution................................................................................. 17 - 20
Demonstration 3: Capacitance and Dielectrics.................................................................... 21 - 30
Demonstration 4: Charging and Discharging Capacitors .................................................... 31 - 34
Technical Support, Copyright and Warranty Information ........................... 35
Product End of Life Disposal Instructions................................................... 36
2
®
ES-9080A 012-07227G Basic Electrostatics System
1
2
3
4
5
5
6
7
Basic Electrostatics System
ES-9080A
Equipment List
Included Equipment Model Number*
1. Basic Electrometer (cables not shown) ES-9078A
2. Electrostatics Voltage Source (cable and AC adapter not shown) ES-9077
3. Basic Variable Capacitor (cable not shown) ES-9079
4. Faraday Ice Pail and Shield ES-9042A
5. Charge Producers (2) and Proof Plane (1) ES-9075B
6. Conductive Spheres (2) ES-9059B
7. Conductive Shapes (2) ES-9061
3
Basic Electrostatics System ES-9080A
®
*Use Model Numbers to expedite replacement orders.
Additional Equipment
PASCO data acquisition Interface and software See PASCO catalog
Charge, Equipotential, and Field Mapper ES-9060
Introduction
Demonstrations of electrostatic phenomenon have traditionally been limited to the simplest
experiments, using the most elementary equipment, because of problems with technique and
apparatus. Moreover, the traditional demonstrations usually gave qualitative rather than
quantitative results. PASCO has attempted to remedy this by designing the complete ES9080A Basic Electrostatics system. This guide will give the instructor enough of a step-bystep explanation to master demonstration techniques. The range of demonstrations in this
guide more than covers the material usually presented in an undergraduate unit on
electrostatics.
Keep in mind the following principles for your electrostatic demonstrations:
• Read the “Equipment Description” of this manual, which provides information about using
the equipment.
Equipment orientations - Arrange the apparatus to be used so that it is sufficiently separated
and neatly arranged to insure that the students can clearly see the setup. Each
demonstration includes a diagram of the suggested equipment setup. A preferred setup
would also use a computer with a PASCO® interface to display the readings from the
Electrometer (ES-9078) in a computer screen that all can easily see. (You can use an analog
display, for example, to show the deflections of the needle, or a digits display to show the
voltage.) If a computer is not available, set the basic electrometer upright to allow the meter
to easily be seen. Always consider how the equipment arrangement may affect charge
distributions. For example, a misplaced power supply can easily change the charge
distribution on a nearby sphere. Finally, always stand behind the demonstration table to
avoid obstructing anyone’s view.
• Earth grounds - Although it is not always strictly necessary, the demonstrator should be
connected to an earth ground. Stray charges on the demonstrator can cripple an experiment.
Also, keep the electrometer grounded unless specific instructions are given to the contrary.
• Avoid unnecessary movement - If the demonstrator walks around or waves his/her arms
excessively, charge can build up in clothing and affect the results.
• Humidity - The PASCO basic electrometer has been designed to minimize the effects of
humidity. However, a particularly humid day can cause charges to leak off any of the
apparatus, radically changing the charge distribution. To help minimize leakage, keep all
equipment free of dust and oil (e.g. from fingerprints). On the other hand, a particularly dry
4
®
ES-9080A 012-07227G Basic Electrostatics System
day can cause charge to easily build up in any moving object, including people. Minimize
all movement when demonstrating on a very dry day.
• Practice - Nothing can ruin the instructive value of a demonstration more than failure due to
a demonstrator’s unfamiliarity with the equipment and procedure.
Before presenting a series of electrostatic demonstrations, the student (and of course, the
instructor) should be made aware of the following:
• The theory and use of the Faraday Ice Pail. (This is adequately covered in the “Equipment
Description” section and in Demonstration 1.)
• The possible distortion of charge density due to improper use of the proof plane. (See the
“Equipment Description” section.)
• Residual charge may build up in the plastic insulator between the handle and disk of the
proof plane and charge producers. Make sure to ground these parts before any experiment.
• The capacitance of the electrometer must be considered when calculating the magnitude of
a charge from the voltage reading of the electrometer. (See Demonstration 3 for the
procedure necessary to determine the electrometer’s capacitance.)
By following the above principles and by practicing, the demonstrator should have a high
degree of success with the demonstrations and find their educational effect of great value.
Equipment Description
Electrometer (ES-9078A)
The Model ES-9078A Electrometer is a voltmeter used for direct measurements of voltage
and indirect measurements of current and charge. Because of its high (“infinite”) impedance
of 1014 it is especially suited for measuring charge in electrostatic experiments. It has a
sensitivity nearly one thousand times that of a standard gold-leaf electroscope, a center-zero
meter that directly indicates charge polarity, and a digits display. The electrometer measures
-11
charges as low as 10
The electrometer includes a signal input cable (shielded), a banana plug patch cord, a signal
output (interface) cable, and a grounding cable (for use with the ES-9079 Basic Variable
Capacitor).
coulombs.
5
Basic Electrostatics System ES-9080A
®
meter display
zero button, ground and
remove excess charge
output for interface
(not shown)
connect to earth ground
connect signal input
cable here
push to turn ON/OFF
Figure 1: Front Panel Controls of the Electrometer
push to select
voltage range
(3, 10, 30, 100) VDC
light emitting diodes
(LEDs) show the
selected range
ground
Figure 2: Electrostatics Voltage Source
30 V
1 kV
2 kV
3 kV
With these features, you’ll find that your electrostatics demonstrations and labs are easier to
perform and, with quantitative data, are more informative.
The electrometer is powered by four AA-alkaline batteries (included) that can be replaced by
opening the back casing of the electrometer. One of the front panel range-indicator light
emitting diodes (LEDs) will blink slowly when the batteries need to be replaced. When
replacing batteries, do not touch any of the components or wires on the integrated circuit
panel because they are all static sensitive.
Electrostatics V oltage Source (ES-9077)
The ES-9077 is a high voltage, low current power
supply designed exclusively for experiments in
electrostatics. It has outputs at 30 volts DC for
capacitor plate experiments, and 1 kV, 2 kV, and 3 kV
outputs for the Faraday ice pail and conductive sphere
experiments. All of the voltage outputs (except for
the 30 volt output) have a series resistance associated
with them which limits the available short-circuit
output current to about 8.3 microamps. The 30 volt
output is regulated, but is capable of delivering only
about 1 milliamp before falling out of regulation. An
AC adapter (not shown) is included.
6
®
ES-9080A 012-07227G Basic Electrostatics System
Figure 3: Variable Capacitor
Movable
plate
Fixed
plate
Binding
post
Figure 4: Charge Producers
Handle
Non-conductive neck
Non-conductive neck
Conductive knob
V ariable Cap acitor (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 char ge 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.
7
Basic Electrostatics System ES-9080A
®
Figure 5: Proof Plane
-
Handle
Non-conductive neck
Aluminum
surface
Conductive knob
Non-conductive neck
in sampled area
equals charge
Figure 6: Proof Plane in Faraday Ice Pail
• Avoid touching the neck during normal use. The oils from your hands will provide a path
for charges to leak off. If you experience a lot of leakage, wash the white non-conductive
neck with soap and water, rinsing generously; the leakage should disappear. Occasionally
clean the disk surfaces with alcohol.
• When you first use the charge producers, or just after cleaning, they may not produce
charges readily. Rub the white surface vigorously on the conductive proof plane disk.
• The charge producers are designed to be used with the ES-9078 Electrometer. They do not
produce sufficient charge for use with a standard electroscope.
The Proof Plane
As shown in Figure 5, the proof plane is an
aluminum-covered conductive disk attached to an
insulated handle. The conductive disk material is
carbon-filled black polycarbonate (about 10
3
) with
an aluminum surface. The nonconductive neck is
14
white polycarbonate (about 10
).
The proof plane can be used to sample the charge
density on charged conductive surfaces. A Faraday
Ice Pail and Electrometer can then be used to
measure the charge density on the proof plane (see
Figure 6).
By touching the proof plane to a surface, the proof
plane will acquire the same charge distribution as
the section of the surface it touched. By measuring
the charge on the proof plane, the charge density
on that part of the surface can be determined. The
greater the charge on the proof plane, the greater
the charge density on the surface where the proof
plane made contact.
When a proof plane is touched to a conductive
surface, the proof plane becomes part of the
conductive surface. If the effect on the shape of the
surface is significant, the sampling of the charge
density will not be accurate. Therefore, always
touch the proof plane to the conductor in such a way as to minimize the distortion of the
shape of the surface.
8
®
ES-9080A 012-07227G Basic Electrostatics System
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Figure 7: Proper use of a
proof plane to sample charge
Proof plane IS tangent to the
surface of the conductor.
Proof plane IS NOT tangent to
the surface of the conductor.
YES!NO!
Figure 8: Faraday Ice Pail
Shield
Pail
insulators
Figure 7 shows the recommended method for using the proof plane to sample charge on a
conductive sphere.
Use the conductive knob on the end of the proof plane to sample the charge density inside a
hollow sphere (such as ES-9061 Conductive Shapes).
Faraday Ice Pail (ES-9042A)
The PASCO Faraday Ice Pail is shown in Figure 8.
Originally designed by Michael Faraday, it works on the
principle that any charge placed inside a conducting
surface will induce an equal charge on the outside of the
surface. It is an excellent product for sampling charges
and charge distributions. The PASCO version illustrated
above consists of two wire mesh cylinders, one inside the
other, mounted on a molded plastic bottom.
The outer cylinder is called the shield. It provides
complete visibility to the inside of the pail and, when
grounded, helps eliminate stray charges and AC fields.
The inner cylinder is the actual pail. The pail is mounted on insulated rods; the pail is 10 cm
in diameter and 15 cm high. When a charged object is placed inside the pail, but without
touching it, a charge of the same magnitude is induced on the outside of the pai (see Figure
6)l. An electrometer connected between the pail and the shield will detect a potential
difference. The greater the charge, the greater the potential difference. So even though the
electrometer will give readings of voltage, it is possible to use those values as relative charge
measurements.
9
Basic Electrostatics System ES-9080A
®
Support base
Conductive sphere
Non-conductive rod
Thumbscrew
Conductive hollow sphere
Conductive
conical shape
Non-conductive rod
Support base
To prevent stray charges from producing erroneous results, it is extremely important that the
Faraday Ice Pail be momentarily grounded prior to starting any experiment. The demonstrator
must also be continually grounded while performing an experiment.
The Charge Producers are used as charged objects to lower into the ice pail. The Proof Plane
is used to sample surface charge densities.
Conductive Spheres (ES-9059C)
The conductive spheres are used to store electrical
charge. The spheres are 13 centimeters (cm) in
diameter and are made of nickel-plated acrylonitrile
butadiene styrene (ABS) plastic. Each is mounted
on a non-conductive rod of polycarbonate (about
1014 ohms) and attached to a stable support base.
Each sphere has a thumbscrew terminal on the lower
half of the sphere for attaching a ground cable or a
lead from a voltage source. The sphere and
insulating rods should be kept free of dirt, grease,
and fingerprints to minimize charge leakage from
the sphere.
Conductive Shapes (ES-9061)
The conductive shapes are special objects upon
which to store electrical charges. Both shapes are
made of nickel-plated ABS plastic. The Conductive
Hollow Sphere is 13 centimeters (cm) in diameter
and has a 3.8 cm (1.5 inch) diameter hole at the top
that allows access to the inside of the sphere. The
Conductive Conical Shape is spherical on one side
and tapers to a bulbous shape on the other side. Each
is mounted on a non-conductive rod of
14
polycarbonate (about 10
stable support base. Each shape has a thumbscrew
ohms) and attached to a
terminal on the lower half of the shape for attaching
a ground cable or a lead from a voltage source.
The Conductive Hollow Sphere allows you to
measure the amount of charge on the inside of a
charged conductive sphere.
The Conductive Conical Shape allows you to
measure the difference in charge density from one
end to the other of the shape and compare the
distribution of charge density to that of a charged
conductive sphere.
10
®
ES-9080A 012-07227G Basic Electrostatics System
NOTE: When handling the conductive shapes, take care to keep each shape and nonconductive rod free of dirt, grease, and fingerprints to minimize leakage of charge from the
shapes.
Five binding posts allow the voltage source and/or the electrometer to be connected to
components.
NOTE: The proof planes can be used to test for charge polarity on conductors of any shape.
However, for accurate readings of charge density, the conductor surface sampled has to be
considerably larger than the disk of the proof plane and have a relatively large radius of
curvature at the point of contact.
Electrometer Operation and Setup Requirements
The controls on the front panel of the electrometer are explained in Figure 1. Whether you are
using the electrometer to measure voltage, current or charge, the setup procedure should be
followed each time you turn on the electrometer.
Warning:
To avoid electrical shock and/or injury, observe the following safety precautions:
1. Never use the electrometer for measuring potentials more than 100 volts.
2. Never connect the electrometer to an electrostatic generator, such as a Van de Graff
generator of a Wimshurst machine.
3. Never touch the signal input leads until you have grounded yourself to an earth ground. A
person walking across a rug on a cool, dry day can easily acquire a potential of several
thousand volts.
Setup
1. Connect the signal input test lead to the signal input BNC connector of the electrometer.
2. Connect the ground post of the electrometer to an earth ground.
3. Push the power button ON. One of the range switch LEDs will blink twice in quick
succession.
4. Press the ZERO button to z ero the meter . The LE D in the meter display will align with “0”
and the digits display will read “0.0”. You’re now ready to use the electrometer to measure
charge, current or voltage.
11
Loading...