Post on 07-Apr-2022
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.