Download Charges and Static Electricity

Lets begin with some questions.
1) What is electricity made of?
2) How are static electricity and the electricity
found in our homes similar and different?
3) What is electricity's relationship with
magnetism?
Static Electricity and Charges
Magnets, Static Electricity,
Electricity, OH MY!!
• You are all familiar with magnets, static
electricity, and electricity. However did you
know that all three are related to one another?
• All three (magnets, static electricity, and
electricity) are the result of a single property
of matter...electric charge.
Atoms
• The electron is negatively charged.
• The proton is positively charged.
• The neutron has no charge, it is neutral.
Charge
• Most things have the same number of electrons
and protons in them, and they don’t have any
overall charge.
• If this isn’t true though interesting things can
happen.
Gaining Charge
– What are atoms made of?
– What does a neutral charged atom look like?
– What does a positively charged atom look like?
– What does a negatively charged atom look like?
– What is the only thing that moves in an atom that
makes it positively, negatively, or neutrally
charged?
– Remember protons and neutrons do no move from
atom to atom. Its only the electrons.
Charge
Lets imagine that we have an object that is
filled with atoms. Well some of these atoms
can have different “charges” based on the
number of positive and negative atoms the
object will have a positive, negative, or neutral
charge.
We will draw atoms, just "+" and "–" to
illustrate the overall charges
Charge
We will draw atoms, just "+" and "–" to
illustrate the overall charges
e.g. a neutral object
5+
5overall charge 0
Charge
We will draw atoms, just "+" and "–" to
illustrate the overall charges
e.g. a positive object
5+
3overall charge 2+
Charge
We will draw atoms, just "+" and "–" to
illustrate the overall charges
e.g. a negative object
5+
8overall charge 3 -
What is Static Electricity?
Static Electricity: an imbalance of electric
charge on the surface of an object.
• The object that has got extra electrons is now
negatively charged
• The object which has lost electrons is positively
charged.
• Its called static electricity because the charges
build up in only one area.
What is Static Electricity?
Law of Electric Charges:
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
Review
• What are atoms made of?
• What is the only thing that makes an atom or an
object “charged” or neutral?
• What does a positively charged atom look like?
• Negative?
• Neutral?
• An object has become positively charged. What has
happened?
• Negative?
Review
• Your science teacher has prepared the room for
the class's entry by suspending several inflated
balloons from the ceiling. Upon entering the
science room, you observe two balloons being
drawn towards each other. The attraction of
these balloons for one another provides
evidence that ______.
• As you look around the room, you observe two
other balloons being pushed away from each
other. The repulsion of these balloons from one
another provides evidence that ______.
Changing Charge
• How can we change a charge of an object?
– In order to change a charge we need to have
electrons move from one object to another.
– We can charge objects 3 ways
• Friction
• Induction
• Conduction
Friction
• Transfer of electrons between the two objects
that are rubbed together.
• When object A is rubbed against object B the
atoms in object A pull the electrons away from
object B.
• Both objects are now charged. Object A is
negative and B is positive.
A
B
Friction
• Different materials have different affinities for
electrons. Some have a strong affinity (love)
for gaining electrons. Others have a lower
affinity and easily give off or lose electrons.
Triboelectric Series
• The materials highest on
the table will have the
greatest tendency to
acquire the negative
charge. Those below it
would give up their
electrons easily and
become positively
charged.
Triboelectric Series
Celluloid
Sulfur
Rubber
Copper, Brass
Amber
Wood
Cotton
Skin
Silk
Cat Fur
Wool
Glass
Induction
• Charging can occur when materials are not in
contact with one another. The build up of
charge without direct contact is called
induction.
•
Page 141
Induction
Conduction
• Charging by conduction involves the contact
of a charged object to a neutral object. The
neutral object will take on the same charge as
the object that it comes in contact with.
Conduction
Conduction
What about the shock?
• When an object builds up a large amount of
charge it wants to get back to “normal”. It
wants to get back to being balanced.
• When an object comes close that is either the
opposite charge or a neutral charge, the
electrons literally jump to the other object.
• This is called a static discharge. Once this
happens both objects usually return to a neutral
state.
What about when there is not a
shock?
• Sometimes we objects can absorb charge and
the charge moves to the ground. This is called
grounding.
• There is no shock because it has moved away
from the person/object and into something
else.
• If the object is “grounded” the charge will be
absorbed in the ground and the object/person
will have no electrical charge.
Static Electricity
•
•
•
•
What is electricity made of?
Why do we call it “static” electricity?
How do we build up a charge?
What happens when we rub to objects
together?
• Why does it shock you?
• What charge do the objects have after the
shock?
• What are the law of electric charges?
Why not static electricity?
• If static electricity and electrical current are the
same thing (electrons), why don’t we use it as
a power source?
– Static electricity is not stable enough to be a
continuous or regular source of energy.
Potential and Kinetic Energy
Remember all forms of energy have kinetic and
potential energy.
Analogy
The electric field is the space
around an electrical charge
just like
a gravitational field is the space
around a mass.
Electric Field
• Space around a charge.
What is the difference?
Electric Field Lines
Electric Field Lines of two Positive
Charges
Electric Field Lines
• Lines that indicate the strength and
direction of the electric field.
• The more dense the lines, the stronger the
field.
Which field is stronger?
• A
B
Electrical Potential
• Electricity has potential:
– This energy comes from the charge particle has
due to its position in an electric field.
– Because like charges repel, it takes energy to push
a charged particle closer to another particle with a
like charge. That energy is stored as the electric
potential energy. These particles can move and
want to/will when it is free to move.