Transcript Magnet Notes

MAGNET NOTES!
WHAT IS A MAGNET?
• A magnet is any
material that attracts
iron or things made of
iron.
HISTORY OF MAGNETS
• Over 2,000 years ago,
Greeks discovered a
mineral that attracted
things made of iron
• Found in a part of
Turkey called
Magnesia, so they
called it Magnetite
MAGNETIC PROPERTIES
• Magnetic Poles
• Magnetic Forces
• Magnetic Fields
PROPERTIES OF MAGNETS
• Magnetic Poles
• Every magnet has
a north and south
pole-points on a
magnet that have
opposite magnetic
qualities
• Magnetic Forces
– The force of
attraction or
repulsion magnets
exert on each
other
ATTRACTION/REPULSION
• Examples of Repulsion:
• Example of Attraction:
MAGNETIC FIELDS
• The region around
a magnet in which
magnetic forces
can act.
WHAT ARE THE ATOMS INSIDE OF A MAGNET
DOING?
• As negatively charged electrons move around, they
make, or induce, a magnetic field.
• In most material the magnetic field of individual
atoms cancel each other.
• In some materials the north and south poles line up
in a domain (place where groups of atoms are
found).
• If most of the domains in an object align they can
combine to make an entire object magnetic.
WHAT DOES THE INSIDE OF A MAGNET LOOK
LIKE?
Inside a non-magnetic object
Inside a magnetic object
CAN MAGNETS BE DEMAGNETIZED?
• When a magnet’s domains move, the magnet is
demagnetized and loses its magnetic properties.
• This can be done by:
• Dropping a magnet
• Hitting it too hard
• Putting a magnet in a strong magnetic field that is opposite to its
own
• Increasing the magnet’s temperature-with a higher temperature,
atoms vibrate faster and the atoms in the domains may no longer
line up
MAKING A MAGNET
To make a magnet out of something made
of iron, cobalt, or nickel:
•
Line up the domains by rubbing the object with one
pole of a magnet
•
Domains in the object will line up with the magnetic
field of the magnet
•
This is why a magnet can pick up an unmagnetized
object like paper clips
• When a magnet is close to the paper clip, some
of the domains in the paper clip line up with the
field of the magnet.
• When the magnet is removed, the paper clip’s
domains become scrambled again.
KINDS OF MAGNETS
Temporary Magnets
Permanent Magnets
• Made from materials that are
easy to magnetize, but lose their
magnetism easily.
• Difficult to magnetize and keep
their magnetic properties longer
than temporary magnets.
• Soft iron is iron that has not been
mixed with any other materials
and can be made into temporary
magnets
• Some permanent magnets are
made with alnico-an alloy made
up of aluminum, nickel, cobalt,
and iron.
• The paper clip and nail in the
mini-lab were temporary
magnets.
WHAT WOULD HAPPEN IF YOU CUT A MAGNET?
• Would you end up with one north pole and one south pole?
• NO
• When you cut a magnet, you get two magnets, each with its own
north and south pole.
• Why?
• A magnet has poles because its domains are lined up, and
each domain is like a very tiny magnet with a north and
south pole, so even the smallest pieces of a magnet have a
north and south pole.
MAGNETIC FIELD NOTES
MAGNETIC FIELDS
• Region around a magnet in which
magnetic forces can act
• Shape is shown with lines drawn
from the north pole of the
magnet to the south pole, called
magnetic field lines
• The closer together the
magnetic field lines are the
stronger the magnetic force is
• What part of the magnet has the
strongest magnetic force? How
can you tell?
• AT THE POLES – magnetic
field lines are closest together!
MAGNETIC FIELD INTERACTIONS
Two Like Poles
Two Opposite Poles
THE EARTH AS A MAGNET.
• Scientists think that the
earth’s magnetic field is
made by the movement of
electric charges in the
Earth’s liquid outer core,
which is made out of iron and
nickel.
• When the Earth rotates, the
liquid in the core flows
• When the liquid flows, electric
charges move, which makes a
magnetic field
USING A COMPASS
• How does a compass
work?
• The compass needle
points north because
its north pole is
attracted to the earth’s
magnetic south pole.
• What does this mean then?
• The earth has a very
strong magnetic field
NORTHERN/SOUTHERN LIGHTS
• Auroras are made by charged
particles from the sun hitting
oxygen and nitrogen atoms in the
air.
• The atoms become excited and
give off light
• Auroras at north pole are called
northern lights, or aurora borealis
• Auroras at south pole are called
southern lights, or aurora
australis
WHY ARE AURORAS ONLY AT THE POLES?