Electric Charge and Static
Electricity
Electric Charge
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1.
2.
3.
All matter is made up of atoms
Atoms contain
Protons (+)
Neutrons (0)
Electrons (-)
What is Static Electricity?
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Static electricity occurs when there
is a build up of electric charge on
the surface of a material.
It is called static electricity because
the charges don’t move.
The electricity we use everyday
involves moving charges.
What is charge?


To understand charge we have to
look at things on an extremely small
scale.
We have to try and understand
things that we can’t even see with
the most powerful microscope.
Atoms!
The atom
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Everything we see around us
everyday is made of atoms.
We can’t see individual atoms
because they are so small.
In fact the diameter of an atom is
about 0.0000000001m
In the air in your classroom there are
about
1500000000000000000000000000
atoms.
What is inside the atom?

The atom is made of 3 sorts of
particles.
The electron
The proton
The neutron

We can imagine each as a tiny little
ball.
Inside an atom

The protons and
neutrons sit
together in a
lump in the
middle called the
nucleus.

The electrons
orbit around the
nucleus, a bit
like the planets
orbiting the Sun.
Most of the atom is empty space if
atoms were the size of football
fields, the nucleus would be a
grain of sand in the middle and the
electrons would be orbiting around
the edge.
.
Charge
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The electron is negatively charged.
The proton is positively charged.
The neutron has no charge, it is
neutral.
Charge
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Most things have the same number
of electrons and protons in them.
They don’t have any overall charge.
If this isn’t true interesting things
can happen.
How do charges behave?


What do you know about magnets?
2 north poles will repel each other,
but a north and a south put
together will attract one another.
opposites attract, likes
repel.
How do charges behave?

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Exactly the same thing happens
with charges.
2 positive charges put together will
repel each other.
Put a positive charge near a
negative charge and they will
attract each other.
A charged object may even attract a
neutral one. WHY?
Law of Electric Charges

The law of electric charges states
that like charges repel, and
opposite charges attract.

Protons are positively charged and
electrons are negatively charged,
so they are attracted to each other.

Without this attraction, electrons
would not be held in atoms.
Recall This?
The Fundamental Forces
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The strong nuclear interaction is very
strong, but very short-ranged. It acts only
over ranges of order 10-13 centimeters and
is responsible for holding the nuclei of
atoms together. It is basically attractive,
but can be effectively repulsive in some
circumstances.
The electromagnetic force causes electric and magnetic effects such as the repulsion
between like electrical charges or the interaction of bar magnets. It is long-ranged, but
much weaker than the strong force. It can be attractive or repulsive, and acts only
between pieces of matter carrying electrical charge.
The weak nuclear force is responsible for radioactive decay and neutrino interactions. It
has a very short range and, as its name indicates, it is very weak.
The gravitational force is weak, but very long ranged. Furthermore, it is always
attractive, and acts between any two pieces of matter in the Universe since mass is its
source.
How bout This?
The Fundamental Forces

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
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The strong nuclear interaction is very strong, but very short-ranged. It acts only over
ranges of order 10-13 centimeters and is responsible for holding the nuclei of atoms
together. It is basically attractive, but can be effectively repulsive in some
circumstances.
The electromagnetic force causes electric
and magnetic effects such as the repulsion
between like electrical charges or the
interaction of bar magnets. It is longranged, but much weaker than the strong
force. It can be attractive or repulsive, and
acts only between pieces of matter carrying
electrical charge.
The weak nuclear force is responsible for radioactive decay and neutrino interactions. It
has a very short range and, as its name indicates, it is very weak.
The gravitational force is weak, but very long ranged. Furthermore, it is always
attractive, and acts between any two pieces of matter in the Universe since mass is its
source.
What is Static Electricity?
Law of Electric Charges:
1. Opposite charges attract
What is Static Electricity?
Law of Electric Charges:
1. Opposite charges attract
2. Like charges repel
What is Static Electricity?
Law of Electric Charges:
1. Opposite charges attract
2. Like charges repel
3. Charged objects attract neutral objects
Law of Electric Charges
What?
Electric Force
The force between the
charged objects is an
electric force.
The size of the electric force depends on 2 things:
1.
2.
The amount of charge (the greater the charge,
the greater the force)
The distance between charges (the further the
distance, the less the force)
Talk more about this
later…
Electric Field
An electric field is the region around
a charged object where electric
forces can be exerted on another
charged object.
(Repelled or attracted)

Talk more about this
later…
Charged Objects
Atoms do not have a charge
because the number of electrons
and protons cancel each other out.
Ex.
3 protons (+) & 3 electrons (-) = 0

Charged Objects
How do objects get charged?
 They either gain or lose electrons.
 Why not protons?
Ex.
3 protons (+) & 5 electrons (-) =
7 protons (+) & 2 electrons (-) =
What is Static Electricity?
We don't draw atoms, just "+" and "–" to
illustrate the overall charges
e.g. a neutral object
5+
5overall charge 0
What is Static Electricity?
We don't draw atoms, just "+" and "–" to
illustrate the overall charges
e.g. a positive object
5+
3overall charge 2+
What is Static Electricity?
We don't draw atoms, just "+" and "–" to
illustrate the overall charges
e.g. a negative object
5+
8overall charge 3 -
Hi!
How Can You Charge Objects?
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There are 3 ways objects can be charged:
Can you name them?
1.
2.
3.
Friction
Conduction
Induction
**In each of these, only the electrons move. The
protons stay in the nucleus**
Static electricity
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It is this imbalance of positive and
negative charges that causes:
Balloons to stick to walls.
Your hair to stand on end when
brush your hair on a dry day.
And the electric shock you
sometimes get from the door
handle.
Friction
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Charging by friction occurs when
electrons are “wiped” from one object
onto another.
Ex.
If you use a cloth to rub a plastic ruler,
electrons move from the cloth to the ruler.
The ruler gains electrons and the cloth
loses electrons.
Static electricity
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Static electricity is caused when
certain materials are rubbed against
each other.
Electrons can be rubbed off one
material and on to another.
The material that has got extra
electrons is now negatively charged
The material which has lost
electrons is positively charged.
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Conduction
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Charging by conduction happens when
electrons move from one object to another
through direct contact (touching).
Ex. Suppose you touch an uncharged piece of
metal with a positively charged glass rod.
Electrons from the metal will move to the
glass rod. The metal loses electrons and
becomes positively charged.
Induction

Charging by induction happens when charges in
an uncharged object are rearranged without
direct contact with a charged object.
Ex.
If you charge up a balloon through friction
and place the balloon near pieces of paper,
the charges of the paper will be rearranged
and the paper will be attracted to the balloon.
Conservation of Charge
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When you charge something by any
method, no charges are created or
destroyed.
The numbers of electrons and protons
stay the same. Electrons simply move
from one atom to another, which makes
areas that have different charges.
Conductors and
Insulators
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An electrical conductor is a material in
which charges can move easily.
Most metals are good conductors because
some of their electrons are free to move.
Conductors are used to make wires. For
example, a lamp cord has metal wire and
metal prongs.
Copper, aluminum, and mercury are good
conductors.
Conductors and
Insulators
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An electrical insulator is a material in
which charges cannot move easily.
Insulators do not conduct charges very well
because their electrons cannot flow freely.
The electrons are tightly held in the atoms of
the insulator.
The insulating material in a lamp cord stops
charges from leaving the wire and protects
you from electric shock.
Plastic, rubber, glass, wood, and air are
good insulators.
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Static Electricity

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Static electricity
is the electric
charge at rest on
an object.
When something
is static, it is not
moving.
The charges of
static electricity do
not move away
from the object
that they are in.
So, the object
keeps its charge.
Ex. Clothes taken
out of a dryer
Electric Discharge
The loss of static electricity as charges
move off an object is called electric
discharge.
Sometimes,
electric
Sometimes,
discharge
electric
happens
discharge
quickly.
happens
slowly.
Ex. wearing

Ex: static on
clothes
rubber-soled
shoes on
carpet,
lightning
Lightning
What causes lightning?
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Lightning is
actually just
static electricity
on a much larger
scale.
The rubbing is
caused by air
moving around
In thunderclouds
bottom is usually
negative and top
is positive.
Thunder
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
When the lightning flash happens it
heats the air to a temperature 5
times hotter than the surface of the
sun.
This causes nearby air to expand
and vibrate forming the sound we
hear as thunder.
Interesting facts
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Lightning bolts can travel at speeds
of up to 60,000 miles per second.
Every second around 100 bolts of
lightning strike the Earth.
One lightning bolt has enough
electricity to power 200,000 homes.
You are more likely to be struck by
lightning than be eaten by a shark.
Some myths
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Lightning never strikes in the same
place twice.
False, the Empire State Building is
reportedly struck 100 times a year.
Wearing rubber shoes will protect me
in a thunder storm.
False, Lighting is too powerful to be
stopped by half an inch of rubber or
several hundred feet of rubber for
that matter.
How Lightning Forms
Lightning
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Lightning usually strikes the highest point in a
charged area because that point provides the
shortest path for the charges to reach the ground.
Anything that sticks up or out in an area can
provide a path for lightning.
A lightning rod is a pointed rod connected to the
ground by a wire.
Objects, such as a lightning rod, that are joined to Earth by a
conductor, such as a wire, are “grounded.” Any object that is
grounded provides a path for electric charges to move to Earth.
Because Earth is so large, it can give up or absorb charges without
being damaged.
When lightning strikes a lightning rod, the electric charges are carried
safely to Earth through the rod’s wire. By directing the charge to
Earth, the rods prevent lightning from damaging buildings.