Transcript MagnetsHx

Do Now
Given the following objects, a piece of aluminum foil,
a nickel, a plastic figure, a piece of wood, a glass
vase, and some paper clips, predict which objects
will be attracted to a magnet. How do you know?
 Magnetism
repulsion
– force of attraction or
• not all objects are affected by the force of
magnetism
 ex. wood, glass, paper, plastic
• common metals affected by magnetism are iron,
nickel, and cobalt
 They
have a south pole.
 They have a north pole.
• The north and south pole are forces that act on
each other.
 They
are surrounded by a magnetic field.
• Magnetic Poles are points on a
magnet that have opposite magnetic
qualities.
• North and South The pole of a
magnet that points to the north is called
the magnet’s north pole. The opposite
end of the magnet, called the south
pole, points to the south.
 the
north pole of a magnet points North
• it is often called “North-seeking”
 like
magnetic poles repel each other
 unlike
 if
magnetic poles attract each other
the north pole of one magnet is brought
near the north pole of another magnet,
they will repel each other
 if two south poles are brought together,
they will repel each other
•
Magnetic Forces When you bring two
magnets close together, the magnets
each exert a magnetic force on the
other. These magnetic forces result from
spinning electric charges in the magnets.
The force can either push the magnets
apart of pull them together.
 Magnetic
Fields A magnetic field exists
in the region around a magnet in which
magnetic forces can act.
 Atoms
and Domains In materials such
as iron, nickel, and cobalt, groups of
atoms are in tiny areas called domains.
The north and south poles of the atoms in
a domain line up and make a strong
magnetic field.
•
Losing Alignment When domains
move, the magnet is demagnetized, or
loses its magnetic properties.
•
Making Magnets You can make a
magnet from demagnetized material if
you line up its domains with another
magnet.

Cutting a Magnet When you cut a
magnet in half, you end up with two
magnets.
•
Atoms and Domains Some magnets, called
ferromagnets, are made of iron, nickel, cobalt, or
mixtures of those metals. Another kind of magnet
is the electromagnet. This is a magnet made by
an electric current.
•
Temporary and Permanent Magnets
Temporary magnets are made from materials
that are easy to magnetize. But they tend to lose
their magnetization easily. Permanent magnets
are difficult to magnetize, but tend to keep their
magnetic properties longer.

magnetic induction – process by which a
material can be made into a magnet.
 some materials are easy to magnetize
• ex. iron
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
 materials
that are hard to magnetize will
also stay magnetized for a long time
a
magnet that is hard to magnetize but
tends to keep its magnetism is called a
permanent magnet.
•
One Giant Magnet Earth behaves as if it has a
bar magnet running through its center.
•
Poles of a Compass Needle The point of a
compass needle is attracted to the south pole of a
magnet. Opposite poles of magnets attract each
other.
•
South Magnetic Pole near North Geographic
Pole A compass needle points north because
the magnetic pole of Earth that is closest to the
geographic North Pole is a magnetic south pole
•
The Core of the Matter Scientists think
that the Earth’s magnetic field is made by
the movement of electric charges in the
Earth’s core.
•
A Magnetic Light Show Earth’s
magnetic field plays a part in making
auroras. An aurora is formed when
charged particles from the sun hit oxygen
and nitrogen atoms in the air.
 Magnetic
Force and Electric Current
An electric current can cause a compass
needle to move. The needle is a small
magnet. This property is useful in electric
motors.
 Aurora
Borealis
 Aurora
Australis
the interaction between
electricity and magnetism