11-0051_experimentguide

7/29/2019 11-0051_experimentguide

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TABLE OF CONTENTS

INTRODUCTION 2

STATIC ELECTRICITY 2

ATOMS 2

SOLAR SYSTEM MODEL 2

ELECTRON CLOUD MODEL 2

INSULATORS AND CONDUCTORS 3

ELECTRONS INSIDE CONDUCTORS 3

ELECTRONS INSIDE INSULATORS 3

CARDBOARD AND PAPER 3

WATER 3TRIBOELECTRIC CHARGE 4

TRIBOELECTRIC SERIES 4

FUN-FLY-STICK, INSIDE VIEW 4

HOW FUN-FLY-STICK WORKS 5

ELECTROSTATIC INDUCTION 5

POLARIZATION 6

CORONA DISCHARGE 7

LEVITATION PRINCIPLES 8

ARBOR SCIENTIFIC HAS ROYALTY FREE LICENSE TO USE THE WORK PRESENTED HERE

IN COMMERCE.


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Introduction

Playing with the Fun-Fly-Stick is a great way to gain a deep

understanding of static electricity. Fact:

The American physicistRobert Jemison Van de

Graa patented the

Van de Graa genera-

tor in 1931.

The Fun-Fly-Stick is a portable version of the well-knownVan de Graa 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 elds

which are strong enough to be measured, manipulated, felt

directly, played with, and nally grasped at an intuitive level.

Static electricityis the result of an articially 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.

Solar System Model(a.k.a Rutherfords Model ofAtom) 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 dierent 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 Modelclaims 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.

Rutherfords model of atom

( Solar System )

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.

Electron Cloud model of atom


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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 migra-

tion 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 willhave 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 conduc-

tors. If you take a segment of electric wire, you will nd 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 inuenced 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 eld strength that is can withstand

without a breakdown. At the breakdown, the electric eld frees bound electrons, thus

turning the material into a conductor. The breakdown point depends on dierent factors

which include humidity, temperature, thickness of the insulator, as well as the strength ofthe e-eld inuencing 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 conduc-

tive 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 papers high electrical resistance. That is why when we touch the control tube of theFun-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 signicantly 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 impuri-

ties, 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 veryweak 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 denes a place of the material in the triboelectric series. The triboelectricseries 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 tribo-

electric series.

To create static charge we want to choose materials on dierent

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 Graa

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

polyesterpolystyrene

PVC

TeonNegative (captures

electrons)

Fun-Fly-Stick, Inside View

Look at the inner workings of your Fun-Fly-Stick wand. There are two rollers Teon 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.

Ground

Teflon RollerMetal Roller

Rubber Belt

Upper Brush

Lower Brush

TOPBOTTOM


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The Teon 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-Fly-Stick serves as an electric charge accumulator and eectively

replaces the typical spherical metal dome of the Van de Graa

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 touchesthe metal rim surrounding the

button, thus grounding the

Fun-Fly-Stick because the

human body is a great conduc-

tor. 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 Graa generator.

Electrical charges are separated at the point where the rubber belt and Teon rollerspaths separate. As we learned from the triboelectric series, Teon 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 Teon roller and

they ow 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 electrondecient belt. The electrons are carried down to the lower

Teon roller where the cycle is repeated. The lower comb is connected to the operators

nger (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 rst introduce electrostatic induction.

Electrostatic induction is the redistribution of electrical charges in an object caused by

the inuence of nearby charges. In other words, when charged and neutral objects have

no direct contact but the neutral object is placed within the electric eld 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, induc-tion is fairly simple. The electrons either move toward the positive eld 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 electrondecient,

and thus positively charged. This redistribution of charges is called induction.


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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-eld 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 iscalledpolarization.

Lets look closely at the copper combs. First, we have to note that they are excellentconductors 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 eld (e-eld) of the rollers.

Induction in Conductors

Insulator when no e-eld applied

Polarized


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When the e-eld of the negatively charged Teon

roller reaches the tips of the comb, the electrons move

away, leaving the tips of the comb with a positive

charge. The strong e-eld of the roller also ionizes the

surrounding air creating on a very small scale aneect 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 posi-

tively charged tip of the lower comb attracts the

electrons, moving them toward the metal rim of the

power switch to ground them though the operators

body.

The positive ions get attracted to the Teon 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-eld 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-eld of the aluminum roller induces a negative

charge in the comb. The air around the roller becomesionized 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.

Charge Concentration:

Once the charges inside the Fun-Fly-Stick

begin separating, all the charged

components become surrounded by an

electric eld or e-eld. The more chargethe component has or accumulates on it,

the more signicant its electric eld

becomes. The cardboard tube is the

largest charged component with a strong

positive electric eld surrounding it. Each

of the rollers has the second largest

concentration of the charge and the belt

has the weakest electric eld 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 o and power

the Fun-Fly-Stick in a completely dark

room. Observe the insides of the wand.

The discharge will be so insignicant

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 reworksaround the wand.

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 objecttouches 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.


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Levitation Principles

Make a Mylar shape oat following the Quick Start Instructions on the rst page. The

shape oats due to the repelling electric eld 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 distrib-

uted along the entire surface of the shape.

To levitate shapes you need to have two things: a statically charged object (either Fun-

Fly-Stick, latex balloon, or PVC pipe) and a shape able to oat on an electric eld.

To oat, the material has to be lightweight and conductive. For example, a shape made ofthe thinnest paper tissue, Christmas tree tinsel, or a metallic thread will oat because it is

both lightweight and conductive.

Gravity is stronger than the e-eld of the charged object. The material has to be light-

weight to be able to defy gravity. The more weight it has, the lower it sinks (if it even takes

o the wand at all). But why do we choose conductive materials?

A conductive material gets charged almost instantly either on contact or through induc-

tion. 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 redistrib-

uted on the entire surface. Therefore there is little localized repulsion between the insula-

tor and the charged object.

A shape consisting of strands tied together on both ends opens

up into a oating orb, much like a globe with meridians. The

repulsion of like charges within the shape itself causes the shapeto open up and become 3-dimensional.

The shape, when aoat, is surrounded by an e-eld of the same charge as the Fun-Fly-

Stick. It repels only from the control tube of the Fun-Fly-Stick or any other object charged

with the same charge. That is why oating two yers 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-eld. When the oating shape rises higher

and higher, some people try reaching it with the charged Fun-Fly-Stick. This causes the

oating shape rise even higher and escape the e-eld.All the objects surrounding us are mostly neutral. An e-eld approaching a neutral object

causes electrostatic induction in conductors and polarization in insulators. Thus,

when the oating shape nears a wall, a person, furniture, or any other object, its

e-eld causes redistribution of charge in that object. The positive e-eld


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surrounding the oating shape induces negative charge in generally neutral objects. This

in turn causes the oating shape to attract to those neutral objects. If it touches the

object a discharge occurs and the yer loses its charge.

This is why instead of chasing the oating shape that has risen too high with the Fun-Fly-

Stick and repelling it, the best way to get it down is simply to extend your free handtoward it. The Beckoning Hand magic trick when you oat a shape and then make it

follow your hand by approaching its e-eld 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 oating shape with the index

nger 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 againand spring back to life. Repeat several times.

Why does this happen? You body is a conductor. Once

your nger touches a positively charged conductive

shape, the electrons from your body instantly migrate

on to the ying 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 jump-

ing 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-eld 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 oor 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 o.


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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 persons 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 owing 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 nger 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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11-0051_experimentguide