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MAGNETISM
Magnetism – a force to be
reckoned with
Magnetism is the force that
attracts and repels materials
when all the electrons in the
material flow in the same
direction.
Nonmagnetic materials, such as
plastic, glass and wood, have
electrons that flow in different
directions.
Making Magnets
Many metal objects can be
magnetized rubbing them
along a magnet in one
direction.
Demagnetization may
occur when these materials
are heated or if the magnet
is dropped or struck with a
hard blow.
Magnetism
A magnetic pole is the
area of a magnet where
the magnetic effect is
strongest. A tiny area of
each magnet, called the
domain, is magnetized
due to the flow of
electrons.
Attraction and repulsion
Magnetic Fields
When a magnet touches a paper
clip, the electrons in the paper
clip begin to spin in the same
direction as the electrons in the
magnet, making the paper clip
magnetic.
Once the paper clip is pulled
outside the magnet's magnetic
field, it loses its magnetism, and
the electrons in the paper clip
begin spinning in all sorts of
different directions again.
Magnetic Fields
• A magnetic field is the region of magnetic force
around a magnet.
• A magnetic domain is when all magnetic fields
are lined up in the same way.
Magnets
Metals can be made
into magnets by
placing them in a
strong magnetic field
However they will
lose magnetism
quickly after being
removed from the
magnetic field.
A permanent magnet is a
magnet made of a material
that maintains magnetism,
such as iron, nickel, and
cobalt. Iron is the strongest.
More Magnetism
If you cut a magnet is
cut in half, each piece
retains its magnetic
properties. This will
happen no matter how
many times you cut it
since you are making a
physical change.
Earth as a Magnet
Earth has a magnetic field with two
main poles. This magnetic field
enables us to use compasses
Our planet's rotation causes molten
iron-nickel in its outer core to
circulate, creating electrical currents
and a magnetic field (right). Think
electromagnet on a planet size scale.
Electromagnets
Electromagnets are strong
temporary magnets. A
changing magnetic field
causes current to flow in a
conductor.
Scientists call this property
electromagnetic induction.
It allows us to convert
mechanical energy, a form
of the kinetic energy of
motion, into electricity.
Michael Faraday
http://www.magnet.fsu.edu/education/tutorials/java/electromagneticinduction/inde
x.html
In this interactive, replicate Faraday’s experiment to prove that electricity could be
generated from magnetism, now known as electromagnetic induction
A magnetic field is in the same direction as the electric
current.
Magnetism can be
turned on and off
You can make an
electromagnet by
wrapping a wire
around a piece of
iron and sending a
current through the
wire with a battery.
To increase the strength of
an electromagnet:
Increase the voltage or
current
Increase the number of
loops of wire
Make the loops of wire
tighter
Increase the amount of
metal in the core
Use iron as the core
Classroom electromagnet
vs. commercial electromagnet
Motors
Generators
A generator is a motor opeating
backwards. It converts
mechanical energy into
electricity.
Most of the electrical energy we
use comes from electric
generators.
The picture to the left shows an
early model of a General Electric
alternating current generator.
Transformers
• A transformer is a device that increases or
decreases voltage.
• transformer – consists of two separate
coils of insulated wire wrapped around an
iron core
• step-up transformer – a transformer that
increases voltage
• step-down transformer – a transformer
that decreases voltage
Medical uses – the MRI
•
MRI scanners, like X-rays and CT scanners, take internal pictures by generating three
dimensional images in any orientation and at any depth in the body. Doctors can
examine soft tissues like the spinal column and cord, identify multiple sclerosis,
tumors, tendonitis, strokes and many other conditions. They produce better oictures
than Xrays and CT scans but are also more costly.
Internet resources
http://www.albany.edu/~ms547669/enacmag.html Interactive pictured
below. What will a magnet pick up?
http://www.magnet.fsu.edu/education/tutorials/timeline/
Historical timeline
http://www.fossweb.com/modules3-6/MagnetismandElectricity/
Foss Webs interactives
Internet review games (easy)
http://www.quia.com/rr/245161.html
Marta’s Magnets (elementary review,
millionaire style)
http://www.quia.com/cb/54471.html
Jeopardy style magnet and electricity
Internet review games (harder)
http://www.quia.com/quiz/2902523.html
Quiz
http://www.quia.com/ba/174414.html
Battleship style review
http://www.quia.com/quiz/2407324.html
Quiz based on Pearson chapters 1 & 3 electromagnets and
magnetism
http://www.quia.com/pop/89861.html
Uses of magnetism cloze activity
http://www.quia.com/rr/95479.html
Millionaire style review of electricity and magnetism
Compasses in Magnetic Fields
http://www.magnet.fsu.edu/education/tutorials/java/magcompass/index.htmlCompasses in Magnetic Fields
A tutorial that allows you to experiment with a compass to see how it
responds to magnetic fields