Electrostatics Notes (644)

Charge!

! Have you ever walked across the carpet and

gotten “shocked” when you touched the

doorknob?

! What about static

cling? Have you ever

gotten to school only

to be embarrassed

when someone points

out the sock sticking

to your back?

What’s going on in these cases?

Why did they occur?

Review: Atomic Structure

3 Basic Particles make

up Atoms:

1.___________

2.___________

3.___________

Charge

! Protons & Electrons have a property called

_________ ________

– Protons: ________ electric charge (+)

– Electrons: _________ electric charge (-)

– The strength of the positive charge on a proton

is the ______ as the strength of the negative

charge on the electron

Charge cont.

! Neutrons ___ _____ have charge

– Neutrons: __________

Neutrons must be

from Switzerland

Particle Charge Summary:

! Particles may be charged (positive or

negative) or neutral (not charged)

Electrons

Neutrons

Protons

ChargeParticle

Basically…! Oppositely charged particles _______ each other

– Ex: Protons (+) and Electrons (-) attract

! Particles with the same charge ______ each other

– Ex: 2 Electrons (-) would repel each other

– Ex: 2 Protons (+) would repel each other

! Particles with neutral charge _____ ______

interact

– Neutrons do not attract or repel each other

– Neutrons do not attract or repel electrons or protons

In the real world, we rarely deal

with individual charged particles

! Everyday objects are made of _____ of

atoms

! Most atoms have an ______ number of

protons and electrons

! Therefore, atoms are _____________

– Remember, even though atoms are neutral,

they are still made of charges

What does it mean to say that an

object is neutral?

! A neutral object has ____ net (overall)

charge

! A neutral object has ________ amounts of

positive and negative charge

What does it mean to say that an

object is charged?

! A __________ object has a net charge

! A _______ charged object has a greaterquantity of positive charge than negativecharge

! A ________ charged object has a greaterquantity of negative charge than positivecharge

Electrons move, Protons don’t!

! Protons ________ move!

– Protons are very massive. They have too much

inertia.

– They are in the center of the atom.

! Electrons are outside the nucleus.

– It is easier to move particles on the perimeter.

What do you have to do to make

an object positively charged?

! You need to ___________________

! _____________________________

! _____________________________

What do you have to do to make

an object negatively charged?

! You need to __________________

! ____________________________

! ____________________________

So, a charged sock can stick to

my shirt… Does that mean that

my shirt is charged?

! ________________

! Remember that a neutral object is made upof _____________ positively andnegatively charged particles.

! A charged object (positive or negative) willbe attracted to a neutral object.

– We’ll discuss exactly why later…

Conductors vs. Insulators

! Conductors:

– _________ bound

electrons

– ______ the flow of

electrons

– Examples:

___________

! Insulators:

– _______ bound

electrons

– _____ the flow of

electric charge

– Examples:

________________

____________

So what is happening when you

rub a balloon on your head and it

becomes charged? Is friction

creating charge?

! No! Charge cannot

be___________ or

_____________

– Conservation of Charge

! Charges are being

______________…

There are 3 Charging Methods

! Objects can be charged by

– _________________

– _________________

– _________________ (triboelectricity)

Conduction! Requires the objects to be in __________ (or

close enough for a spark)

! ___________ are exchanged

! Works best from conductor to ___________

Induction! A charged object charges a neutral conductor

____________ contact

! The conductor _____ make contact with a_________ object (often the ground)

! The conductor ends up with a charge __________that of the charged object brought near

Triboelectric (friction)

! Two __________

materials are

brought into contact

and charge is exchanged

! The contact often

involves ____________

! Works best with

_____________

More on Triboelectricity

! Charge _________ occurs when two

insulators are rubbed together

! One of the insulators is more likely to

_______ electrons and the other insulator is

more likely to donate electrons

! CHARGE IS NOT CREATED! Electrons

are simply being _______________.

" Electron Donors(objects that give electrons

become positive)

(objects that take electrons

become negative)

" Electron Grabbers

The Triboelectric Series

You rub a balloon against your hair, and the hairbecomes positively charged. This means that

A. Electrons moved from the balloon to your hair.

B. Protons moved from the balloon to your hair.

C. Protons moved from your hair to the balloon.

D. Electrons moved from your hair to the balloon.

E. The rubbing destroyed electrons in your hair,leaving it positive.

Triboelectric Charging

A Triboelectric Sequence

ELECTRON GRABBERS ELECTRON DONORS

Rubber Amber Cotton Silk Cat fur Wool Glass Rabbit fur

If you rub cotton with amber, which becomes positive?A. Amber B. Neither C. Cotton

Which of the following can make glass negative?A. Amber B. Cat fur C. Rabbit fur

Triboelectric Series

Neutralizing/Grounding Objects

! When a charged object comes in contact

with a very large, neutral conductor, the

object becomes _______________.

! ______ itself is a large, neutral conductor,

so it neutralizes charged objects quite well.

Review

! Charged objects exert forces:Like repels like

Opposites attract

Charged objects and neutral objects attract

! How objects get charged or neutralized:Conduction

Induction

Triboelectric

Grounding

The End!

HOORAY!!!