Transcript ELECTRICITY AND MAGNETISM The magnetic field created by an

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Thank you,
Vicki Hughes
Labs and Activities for this Presentation:
Balloon Hair
Christmas Lights and Batteries
ELECTRICITY AND MAGNETISM
Electric charge is a physical property of particles causing them
to attract or repel each other WITHOUT TOUCHING!
Step 1: Scuff your feet as you walk across carpet.
Step 2: Touch a metal doorknob.
Step 3: Say OUCH! because you just got a shock!
You were shocked by the
doorknob because of
moving electric charges.
Atoms are neutral when they have the same number of
electrons and protons.
-
+
Atoms become positively charged when they have fewer
electrons than protons. They are then called CATIONS.
-
+
Atoms become negatively charged when they have more
electrons than protons. They are then called ANIONS.
-
+
-
All electric charge is based on the protons (+ charge) and
electrons (- charge) in atoms.
Opposites attract!
+
+
Like charges repel.
+
-
-
-
Like charges repel.
Electric Force is the
attraction or repulsion
between charged particles.
An ELECTRIC FIELD is a space around a charged particle where
the particle exerts a force.
+
-
OPPOSITE fields attract each other.
-
+
-
LIKE fields repel each other.
+
+
+
The buildup of charges is
known as static electricity.
Friction and Electric Charge
A balloon rubbed against your
hair will cause it to transfer
electrons from your hair to the
stronger balloon.
The hair becomes + and the
balloon becomes - .
The hair is attracted to the
balloon.
Balloon Hair
Static discharge occurs when built up
static charge is suddenly released.
Electric Current
Electric Current is a continuous flow of electric charges.
Water can flow.
People can flow.
Electrons can flow.
Energy Stick Demo
Current is measured as the amount of charge that flows past a
given point in a certain amount of time.
Electric current can flow in one direction…Direct Current:
or it can keep changing directions…Alternating Current:
Potential Difference (Voltage) = difference between starting point
and ending point of a current.
high
low
Resistance is the opposition to the flow of electric currents.
Resistance is caused by
electrons bumping into
particles in matter.
Resistance is futile?
Nah, but it slows you
down!
Georg Ohm
George Ohm
Conductors have LOW resistance and allow current to flow.
Let the current flow!
George Ohm
Insulators have HIGH resistance and DO NOT allow current to flow.
Stop that current flow!
Conductors and Insulators Electric Fence 0:53
http://www.youtube.com/watch?v=4SIT0aU_FRw
George Ohm
Insulated wire is made of conductive metal wire
surrounded by a nonconductive plastic or rubber coating.
George Ohm
Semiconductor = partially conducts
• circuits can be carved into the surface
• circuits are good conductors
• very energy-efficient
Superconductor = very high conductivity when cold
• more efficient than regular conductors
Any
Questions?
NYC Blackout 10:14
http://www.youtube.com/watch?v=6nt0njgVmv4
MAGNETISM
Aurora Borealis is a result of the response of
Earth’s magnetic field to solar flares.
Properties of MAGNETS
Magnet = object that attracts certain materials such as iron.
Quick Lab: Wooly Willy
Properties of MAGNETS
Magnetic Poles
• A magnetic pole is a region
where the magnet is strongest.
• All magnets have two magnetic
poles.
• The poles are called “north”
and “south” because they
line up with the Earth’s axis.
Properties of MAGNETS
Magnetic Poles
• If you cut a magnet apart in the
middle, it will
establish two new poles.
• Pieces of magnets will always
have a north and south pole.
N
S
Poles are on faces.
N
N
N
S
S
MAGNETIC FORCE
Magnetic Force is the force exerted over a distance.
Repulsion = pushing
Attraction = pulling
REPELS!
ATTRACTS!
N
S
N
Activity: Discovering Magnets
S
MAGNETIC FIELD
A Magnetic field is a space around a magnet that exerts a force.
N
S
N
S
When two OPPOSITE magnetic fields interact, they
bend toward each other and pull.
N
S
N
S
When two of the same magnetic fields interact, they
bend away from each other and push.
N
S
S
N
MAGNETISM
Magnetism is due to the
movement of electrons.
http://www.wimp.com/magnetswork/
ELECTRICITY AND MAGNETISM
Electromagnetism is magnetism produced by an
electric current.
Hello! I am Dr.
Oersted. Please
join me.
Let me tell you
how I discovered
the relationship
between electric
currents and
magnetic fields.
Denmark
1820
ELECTRICITY AND MAGNETISM
It all happened like
this…
I was trying to
show my students
that electricity and
magnetism are not
related. I placed a
wire with electric
S
current flowing
through it next to a
magnet, and
nothing happened.
Denmark
1820
N
ELECTRICITY AND MAGNETISM
After class, a student
held the wire near
the magnet again,
but in a different
direction. To my
surprise, the pointer
of the magnet swung
toward the wire so it S
was no longer
pointing to Earth’s
magnetic north pole.
With more
experiments, I was
able to show the lines
of magnetic fields.
Denmark
1820
N
ELECTRICITY AND MAGNETISM
I’m so proud
of my little
pooky-bear!
Aw, mom!
Denmark
1820
Thank you for visiting. Good
night everyone.
ELECTRICITY AND MAGNETISM
The magnetic field created by an
electric current flowing through
a wire actually surrounds the
wire in circles.
This magnetic field is stronger as
more current flows through the
wire.
The direction of the magnetic
field depends on the direction
the current is flowing.
ELECTROMAGNETISM
Solenoid = a coil of wire with
electric current flowing
through it, giving it a
magnetic field.
ELECTROMAGNETISM
The magnetic field around a
coiled wire has north and
south poles like a bar
magnet.
ELECTROMAGNETISM
The magnetic field around
a coiled wire is stronger
because each
turn of the wire has its
own field.
Therefore, more coils mean
stronger magnetism.
31 coils
16 coils
ELECTROMAGNETISM
Solenoids are the basis for
electromagnets.
Electromagnet =
solenoid wrapped around
a bar of iron.
How to make an electromagnet 4:58
http://www.youtube.com/watch?v=emlzh9XXWgQ
ELECTROMAGNETISM
Electromagnetic induction =
generating electricity in a
wire by moving a magnet
nearby.
How to make an electromagnet 4:58
http://www.youtube.com/watch?v=emlzh9XXWgQ
ELECTROMAGNETISM
Project Assignment: (Works = 100; Doesn’t work = 90)
Projects count as test grades!
Make your own electromagnet using a nail, some wire, and a
battery. We will test your battery in class.
http://www.youtube.com/watch?v=nMmldOU6t8I
ELECTROMAGNETISM
Using electromagnets
http://www.youtube.com/watch?v=JWh2qT9yiTo
ELECTRICITY
Electric transformers use electromagnetic induction (moving
magnetic fields past electric fields) to change the voltage of
electric current.
ELECTRICITY
The number of coils on each side determines if the current is
increased or decreased as it flows through the transformer.
ACT L17
Any Questions?
Power of Electricity (Transformer Explosions) 10:09
http://www.youtube.com/watch?v=yX5TIDLvMyw