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TABLE OF CONTENTS
INTRODUCTION
STATIC ELECTRICITY
ATOMS
SOLAR SYSTEM MODEL
ELECTRON CLOUD MODEL
INSULATORS AND CONDUCTORS
ELECTRONS INSIDE CONDUCTORS
ELECTRONS INSIDE INSULATORS
CARDBOARD AND PAPER
WATER
TRIBOELECTRIC CHARGE
TRIBOELECTRIC SERIES
FUN-FLY-STICK, INSIDE VIEW
HOW FUN-FLY-STICK WORKS
ELECTROSTATIC INDUCTION
POLARIZATION
CORONA DISCHARGE
LEVITATION PRINCIPLES
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Introduction
Playing with the Fun-Fly-Stick is a great way to gain a deep
understanding of static electricity.
The Fun-Fly-Stick is a portable version of the well-known
Van de Graaff generator (VDG). Large VDG machines are
often used in museums as a fun demo tool to make your
hair stand on end. VDG machines produce electric fields
which are strong enough to be measured, manipulated, felt
directly, played with, and finally grasped at an intuitive level.
Fact:
The American physicist
Robert Jemison Van de
Graaff patented the
Van de Graaff generator in 1931.
Static electricity is the result of an artificially or naturally created imbalance of charges.
Since all matter around us is made up of atoms, which are usually neutral in charge, we
need to understand how this imbalance can be created.
Atoms:
An atom encapsulates positive (protons), neutral (neutrons), and negative (electrons)
charges within it. The positive and neutral charges make up the core or nucleus of the
atom, while electrons carrying a negative charge surround the nucleus. There are several
theories and corresponding models used to describe the structure of an atom. The most
popular models are the Solar System Model and the Electron Cloud Model.
Solar System Model (a.k.a Rutherford’s Model of
Atom) is the most common way to picture an atom.
The model describes electrons orbiting around the
nucleus in a fashion similar to planets orbiting the
Sun. Just like planets have their orbits and are
located at different distances from the Sun, the
electrons have their own trajectory and distance
from the nucleus. This model is still popular in
teaching physics as it is easier to visualize.
The Electron Cloud Model claims that there are no
orbitals. Instead, the electrons are located around
the nucleus within certain boundaries or shells.
These shells are described as the most probable
locations for electrons to be found. The boundaries
are fuzzy and the precise location of the electrons is
unknown. This model is considered more advanced
and is commonly used in chemistry and quantum
mechanics.
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Rutherford’s model of atom
( Solar System )
Electron Cloud model of atom
Typically, the number of electrons equals the number of protons. The outer electrons are
located farthest from nucleus and are held more loosely than the rest. On contact
between two materials, electrons may migrate from one material to another. This migration will create an imbalance of charges. The object whose atoms lost electrons will be left
with a positive charge on it and the object that received or “captured” the electrons will
have a negative charge. This imbalance of charges is what creates static electricity.
Insulators and Conductors
Materials made of atoms that hold on to their electrons very tightly are called insulators.
Materials made of atoms that have a weak attraction to their electrons are called conductors. If you take a segment of electric wire, you will find both types of materials in it. The
silicon that wraps around the metal is an insulator, and the metal inside is a conductor.
Electrons inside conductors are free to move as influenced by various forces. They either
move inside the conductor itself or can migrate to another conductor.
Electrons inside insulators can only move within atoms themselves. They may
stretch the atoms or rotate them but never leave the atoms under normal circumstances.
Nevertheless, every insulator has a maximum electric field strength that is can withstand
without a breakdown. At the breakdown, the electric field frees bound electrons, thus
turning the material into a conductor. The breakdown point depends on different factors
which include humidity, temperature, thickness of the insulator, as well as the strength of
the e-field influencing it.
Cardboard and paper are normally insulators. Cardboard is made of layers of paper so
that we do not have to make a distinction between the two as they are very similar. The
voltage generated by Fun-Fly-Stick turns the paper that we use in the Fun-Fly-Stick and
for the experiments into a conductor with high electrical resistance. This means conductive paper gets to have free electrons. The number of free electrons is much lower than it
would have been in a “normal” conductor and they move much slower within paper due
to paper’s high electrical resistance. That is why when we touch the control tube of the
Fun-Fly-Stick, the electrons from our body run onto the cardboard/paper control tube
very slowly, eliminating instant static discharge through an electric shock. If we were to
touch metal under the same circumstances, we would be significantly zapped.
Water also deserves separate explanation. There is a theory that pure, distilled water is an
insulator. It also has been said that impurities in tap water, (salts and minerals) make
water conductive. In reality, even if you test triple distilled water free of salts and impurities, it shows conductivity. Another theory, which we tend to support, says that water can
ionize in an aqueous (liquid) form to H3O+ and OH- ions. This causes water to be a very
weak electrolyte no matter how many times it is boiled or deionized.
Other liquids like sugar or car antifreeze, do not break down into ions in liquid
form, therefore they do not conduct electricity unless they have impurities.
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Triboelectric Charge
Charge separation that happens due to rubbing or contact between materials is known
as triboelectricity. The tendency for a material to acquire a net positive charge by rubbing
or contact defines a place of the material in the triboelectric series. The triboelectric
series is often referred to as an electronegativity scale. A chemical property that describes
the ability of an atom to attract electrons towards itself is called electronegativity.
If a material is more apt to "capture" electrons when in contact
with another material, it is more negative in the triboelectric
series. If a material is more apt to give up electrons when in
contact with another material, it is more positive in the triboelectric series.
To create static charge we want to choose materials on different
ends of triboelectric table.
Triboelectric series are widely used by those who work on
preventing the triboelectric charge and by those who want to
create it on purpose. For example, static charge buildup can
damage semiconductor devices upon electrostatic discharge
(ESD), thus companies use materials that do not charge each
other upon contact when handling, packaging, and storing
ESD-sensitive electronic devices.
On the other hand, companies that utilize the triboelectric
charge to create static electricity, like to build a Van de Graaff
generator, base selection of the materials that comprise the
“heart” of the VDG machine on the triboelectric series.
Triboelectric series
Positive (gives up electrons)
glass
hair
nylon
wool
fur
silk
aluminum
paper
cotton
rubber
copper
polyester
polystyrene
PVC
Teflon
Negative (“captures”
electrons)
Fun-Fly-Stick, Inside View
Look at the inner workings of your Fun-Fly-Stick wand. There are two rollers – Teflon on
the bottom and aluminum on top.
A rubber belt runs over the rollers.
There are two copper combs/brushes, one on top and one on the bottom. They come as
close as possible to contact with the belt, but never actually touch the belt directly.
BOTTOM
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TOP
Ground
Lower Brush
Teflon Roller
Rubber Belt
Upper Brush
Metal Roller
The Teflon roller on the bottom is mounted on top of the axel
of the motor powering the wand. Lastly, two AA batteries
power the motor. A cardboard control tube snaps on top of
the Fun-Fly-Stick coming into a tight contact with the exposed
part of the upper brush. The cardboard tube of the Fun-FlyStick serves as an electric charge accumulator and effectively
replaces the typical spherical metal dome of the Van de Graaff
generator. The standard VDG device looks like a big aluminum
ball mounted on a pedestal. If you touch the aluminum ball, it
will result in an electric shock discharge, unless you isolate
yourself from the ground. With Fun-Fly-Stick you do not have
to worry about that, you can touch it and nothing will happen
because of the high electrical resistance of paper.
Fun-Fly-Stick Secret:
The lower brush is connected to
the metal rim of the power
button by a wire. By pressing the
power button the user touches
the metal rim surrounding the
button, thus grounding the
Fun-Fly-Stick because the
human body is a great conductor. If an operator is not isolated
from the ground by rubber-soled
shoes or another insulator, the
Fun-Fly-Stick will work the best!
How Fun-Fly-Stick Works
Press the power button on the Fun-Fly-Stick and observe the mechanism of the wand
through the translucent walls.
Below is the general explanation for students who begin learning the basics of static
electricity and the Van de Graaff generator.
Electrical charges are separated at the point where the rubber belt and Teflon roller’s
paths separate. As we learned from the triboelectric series, Teflon “captures” the electrons
from the belt leaving the belt with a positive charge moving toward the aluminum roller.
Immediately, the lower comb “sweeps” the excess electrons from the Teflon roller and
they flow to the ground via the operator. As the positive belt passes over the top metal
roller, free electrons from the accumulator (control tube) are sucked in via the upper
comb and onto the electrondeficient belt. The electrons are carried down to the lower
Teflon roller where the cycle is repeated. The lower comb is connected to the operator’s
finger (ground) through the metal rim of the button.
A smart student will undoubtedly raise the question: “How do combs sweep charges if
they never come into contact with the belt or the rollers?” To answer this question we
should first introduce electrostatic induction.
Electrostatic induction is the redistribution of electrical charges in an object caused by
the influence of nearby charges. In other words, when charged and neutral objects have
no direct contact but the neutral object is placed within the electric field of the charged
one, a separation of the internal charges occurs inside the neutral object.
When a neutral object is a conductor, which means it has freely movable electrons, induction is fairly simple. The electrons either move toward the positive field of a charged
object of move away from it if the object is negatively charged. The electrons concentrate
on one side of the object leaving the opposite side electrondefficient,
and thus positively charged. This redistribution of charges is called induction.
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Induction in Conductors
Insulators hold on to their electrons very tightly.
Charge redistribution still happens but on a much
smaller scale. Electrons move only within atoms
themselves, thus pointing in the same direction
when placed within the e-field of a charged object.
If the charged object is positive, then the electrons
face the object, while if it is negative then the
electrons point away. This re-orientation of atoms is
called polarization.
Insulator when no e-field applied
Polarized
Let’s look closely at the copper combs. First, we have to note that they are excellent
conductors and their electrons move freely inside them. Second, the combs have sharp or
pointy tips which are helpful to induce air ionization around them. Third, the
comb tips are situated within the electric field (e-field) of the rollers.
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When the e-field of the negatively charged Teflon
roller reaches the tips of the comb, the electrons move
away, leaving the tips of the comb with a positive
charge. The strong e-field of the roller also ionizes the
surrounding air creating – on a very small scale – an
effect known as corona discharge. The air breaks
down into electrons and positive ions. The roller
repels the electrons that are in the air and the positively charged tip of the lower comb attracts the
electrons, moving them toward the metal rim of the
power switch to ground them though the operator’s
body.
The positive ions get attracted to the Teflon roller,
adding positive charge to the belt as it moves toward
the roller. The belt carries the positive charge to the
aluminum roller. The roller accumulates the charge.
The pointy tip of the upper brush is situated within
the e-field of the aluminum roller. The other end of
the upper brush is exposed and directly contacts the
inside of the conducting cardboard tube. The positive
e-field of the aluminum roller induces a negative
charge in the comb. The air around the roller becomes
ionized as a result of small scale corona discharge. The
roller attracts electrons from the air while pushing
away positive ions. At the same time, the negatively
charged comb attracts positively charged ions and
repels the electrons. The electrons moving toward the
positive roller encounter the belt on the way. The
electrons give the belt negative charge that gets
carried on to the roller that “captures” electrons.
The cardboard control tube is a conductor with high
electrical resistance. The control tube and the exposed
end of the upper comb have tight contact when the
control tube is mounted on top of the Fun-Fly-Stick.
This allows the control tube to become an extension of
the comb as two conductors join.
On the other hand, the control tube presents itself not
just as a conductor, but
also as a conductive container. When a charged object
touches a conductive container on the inside, the
container receives all the charge. The excess of the
charge concentrates on the outside of the container
and begins dissipating into the air.
Charge Concentration:
Once the charges inside the Fun-Fly-Stick
begin separating, all the charged
components become surrounded by an
electric field or e-field. The more charge
the component has or accumulates on it,
the more significant its electric field
becomes. The cardboard tube is the
largest charged component with a strong
positive electric field surrounding it. Each
of the rollers has the second largest
concentration of the charge and the belt
has the weakest electric field of all.
Charge on the Belt:
The belt in a VDG generator carries both
charges at the same time. Half of the
belt carries positive charge toward the
roller that gives up electrons and the
other half carries negative charge to the
roller that acquires electrons.
+ + + + + + + + + + +
- - - - - - - - - - - - - - - -
Corona Discharge:
Take the cardboard tube off and power
the Fun-Fly-Stick in a completely dark
room. Observe the insides of the wand.
The discharge will be so insignificant
that you may not even see it. However,
touch the exposed end of the copper
comb and you should see a glow around
the rollers. Now, put the cardboard top
back on and power the wand. You may
observe corona discharge around the
wand so bright that the glowing around
the rollers will be seen but visually
disrupted by explosive “fireworks”
around the wand.
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Levitation Principles
Make a Mylar shape float following the Quick Start Instructions on the first page. The
shape floats due to the repelling electric field of the Fun-Fly-Stick.
When you turn the Fun-Fly-Stick on, it begins separating positive and negative charges.
The positive charge gets accumulated on the control tube – the cardboard tube mounted
on top of the wand. When the shape touches the control tube, it acquires positive charge
and immediately repels from the control tube because they now have the same charge.
The shape opens up because it repels within itself due to the same charge being distributed along the entire surface of the shape.
To levitate shapes you need to have two things: a statically charged object (either FunFly-Stick, latex balloon, or PVC pipe) and a shape able to float on an electric field.
To float, the material has to be lightweight and conductive. For example, a shape made of
the thinnest paper tissue, Christmas tree tinsel, or a metallic thread will float because it is
both lightweight and conductive.
Gravity is stronger than the e-field of the charged object. The material has to be lightweight to be able to defy gravity. The more weight it has, the lower it sinks (if it even takes
off the wand at all). But why do we choose conductive materials?
A conductive material gets charged almost instantly either on contact or through induction. Within conductors the charge is free to move about. Thus the excess charges will
move within the conductor until they can no longer move and that will be when they
reach the surface and can go no farther. Therefore, the excess charge on a conductive
shape will be located on the entire surface, causing every part of the shape to repel from
every other part due to repulsion of like charges.
In the insulator the charge is forced to stay where it is located. It does not get redistributed on the entire surface. Therefore there is little localized repulsion between the insulator and the charged object.
A shape consisting of strands tied together on both ends opens
up into a floating orb, much like a globe with meridians. The
repulsion of like charges within the shape itself causes the shape
to open up and become 3-dimensional.
The shape, when afloat, is surrounded by an e-field of the same charge as the Fun-FlyStick. It repels only from the control tube of the Fun-Fly-Stick or any other object charged
with the same charge. That is why floating two flyers at the same time is a challenge; they
repel each other. When you press the button on the Fun-Fly-Stick you increase the charge
on the control tube and thus expand the e-field. When the floating shape rises higher
and higher, some people try reaching it with the charged Fun-Fly-Stick. This causes the
floating shape rise even higher and escape the e-field.
All the objects surrounding us are mostly neutral. An e-field approaching a neutral object
causes electrostatic induction in conductors and polarization in insulators. Thus,
when the floating shape nears a wall, a person, furniture, or any other object, its
e-field causes redistribution of charge in that object. The positive e-field
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surrounding the floating shape induces negative charge in generally neutral objects. This
in turn causes the floating shape to attract to those neutral objects. If it touches the
object a discharge occurs and the flyer loses its charge.
This is why instead of chasing the floating shape that has risen too high with the Fun-FlyStick and repelling it, the best way to get it down is simply to extend your free hand
toward it. “The Beckoning Hand” magic trick when you float a shape and then make it
follow your hand by approaching its e-field and moving the hand away with the same
speed the shape attracts to it, makes people think that your hand has some magnetic
powers. Now we know that it really gains those magnetic powers by induction!
Experiment: Launch a shape and let it rise up to your
eye level. Touch the floating shape with the index
finger of your free hand. It collapses and drops down
lifelessly. Catch it with the control tube of your
activated Fun-Fly-Stick. The shape will expand again
and spring back to life. Repeat several times.
Why does this happen? You body is a conductor. Once
your finger touches a positively charged conductive
shape, the electrons from your body instantly migrate
on to the flying shape, causing it to lose the charge and collapse. Touching it with the
Fun-Fly-Stick charges the shape again. Once the shape has the charge, it repels within
itself and from the wand, creating a feeling of magic.
Experiment: Launch any small shape and put the
palm of your free hand above it. Trapping the shape
between the control tube of the Fun-Fly-Stick and
your palm causes the shape to bounce back and forth.
The process repeats itself creating a vision of a “jumping” shape.
Why? Touching the control tube of the activated Fun-Fly-Stick causes the shape to
become charged with the same charge as the Fun-Fly-Stick and repel. On the way up the
shape meets your hand, touches it, and instantly discharges because your body and the
shape are conductors.
The e-field of the Fun-Fly-Stick pulls the shape toward the wand where it gets recharged
upon contact (or by induction) and repels again, moving up toward your hand. You can
also do the same trick bouncing the shape horizontally.
Experiment: Isolate a person from the ground by having him or her stand on an insulator.
For insulation, you can use interlocking foam floor tiles, rubber-soled shoes, a plastic
sheet, or another insulating material.
Have the person extend one hand with an open palm facing up. Place the Mylar shape on
the open palm. Have the person hold the control tube of the Fun-Fly-Stick with the
other hand. Turn on the Fun-Fly-Stick and observe the Mylar shape slowly expand
and take off.
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Why? Isolating the person from the ground is the same as isolating a large conductive
object from the ground. When the person holds the control tube of the activated wand,
all the charge created by the Fun-Fly-Stick gets transferred onto the conductive object –
the person. The contact between the wand and the isolated person drains the electrons
from the person’s body leaving him/her positively charged. This gives the charged person
the power to levitate the shapes with his/her hands instead of using the Fun-Fly-Stick.
If the charged person, who is being isolated touches another person who is not charged,
this will produce a spark or a zap caused by the electrons flowing from the non-charged
person into the charged person through the point of contact. If the point of contact is the
nose of one person and index finger of another, the spark may be very visible and will
often makes students laugh.
When you charge the person isolated from the ground with the Fun-Fly-Stick, they
receive a positive charge. However, you can also charge yourself with the opposite
charge. To do so you have to also be isolated and hold the Fun-Fly-Stick while charging
another person. Alternatively, you can isolate yourself from the ground and touch a large
conductive object (a door knob, a conductive wall). The positively charged control tube
attracts electrons from the conductive object it touches and transfers them onto you via
the belt and the metal rim of the button.
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