Transcript What is Magnetism???

What is
Magnetism???
Hmmm…
A strangely “attractive”
topic…
• The term comes from the ancient Greek city of
Magnesia, where many natural magnets were found.
- These natural magnets are called lodestones,
which contain magnetite.
• Chinese, as early as 121 A.D. knew that an iron rod
could be brought near a natural magnet and would
acquire and retain these
magnetic properties.
• The use of magnets can
aid in navigation,
which can be traced back
to the 11th century.
The Science in the History

Not until 1819 was there a connection
made between magnetism and electricity.
Danish scientist, Hans Christian Oersted
observed that a compass needle brought
near a wire carrying an electrical current
would make the compass needle move.
History of Science continued


In 1831, Michael Faraday discovered that
a momentary current existed in a circuit
when the current in a nearby circuit was
started or stopped.
Shortly thereafter, Faraday discovered
that the motion of a magnet toward or
away from a circuit could produce the
same effect.
Where can you find magnets, you
ask?
Here is a list of some places you can find magnets:
Headphones
Speakers
Phone ringers
Seal around refrigerator door
Audio and video tape recording and playback head
Credit card magnetic strip
Computer monitor
Computer hard drive
Power supply transformers
Refrigerator magnets
Telephone receivers
FANS…bathroom, ceiling
Electric toothbrush
Garage door opener
Cell phone vibrator
Clocks and Watches
High Speed Trains
Magnetism
• A force of attraction and repulsion
Magnets

Not all objects are effected by the force of
magnetisms.


Glass, wood, rubber, plastic and paper are
examples of items that are NOT influenced by
magnetism.
Common items that are effected by
magnetism are iron, nickel, and cobalt.
Poles of a Magnet
• Area where the magnetic force is
the strongest
North and South
(N & S)
Law of Magnetic Poles
• Opposites attract & Likes repel
Poles CANNOT
be separated!!!
Charges
Like poles repel each other.
Opposite poles attract each other.
Polar Opposites

Poles – two ends of a magnet

every magnet has two poles

north (N) pole AND south (S) pole
even if you break a magnet in half, each half will
have a north pole and a south pole.
•
Magnetic Field
•A
region around a magnet where the
force is the strongest
N
S
The strength of the
field decreases as
the distance from
the field increases.
Magnetic Domains
NOT A
MAGNET!!!
When all of the domains are lined
up, the object becomes magnetized
Temporary Magnets
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a material that is easily magnetized tends
to lose its magnetism quickly
a magnet made of this kind of material is
called a temporary magnet
Making a Temporary Magnet

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Nails made up of atoms have all electrons
spinning in different directions……by rubbing a
magnet over the nail in one direction will get the
electrons to SPIN all in the SAME direction..
This makes the nail into a temporary magnet.
Electromagnets

electromagnet – temporary magnet made
by wrapping a current-carrying wire
around an iron core

the center of an electromagnet is called the
core and is often made of iron.
Demagnetizing a Magnet
• A magnet is no longer a magnet
• The domains are not lined up anymore
Ways to Demagnetize a Magnet
1) Heating
2) Dropping
3) Other Strong Impact