Transcript Magnetism -the attraction of a magnet for another object

Magnetism
Magnetism – the attraction or repulsion of magnetic materials
History of Magnetism

Magnetism was discovered in Magnesia
Greece (which is now Turkey)
 A mineral in rocks that is magnetic was
discovered. This mineral was called
magnetite. The name of these rocks are
called lodestones.
Three Properties of Magnets
Allowed to swing freely, one part of a
magnet will always point North.
 Magnets contain iron and are attracted
to materials that are made of iron.
 Magnets attract and repel other
magnets.

Magnetic Poles
All magnets have a North and South
Pole. At the poles is where a magnet is
the strongest.
 Like poles repel each other.
 Opposite poles attract each other.

Magnetic Fields
The region around a magnet in which magnetic forces act.
Magnetic Earth
Earth is compared to a bar magnet because it has
a magnetic field, poles, and its core consists of
iron and nickel.
Structure of the Atom
Spinning electrons
produce a magnetic
field. This makes the
electrons behave like
tiny magnets.
Magnetic Domains
Magnetic domains are groups of atoms
that have their magnetic fields aligned.
 Magnetized materials have their
domains arranged in the same direction.

Ferromagnetic Materials
Ferro comes from ferrum which means
iron in Latin.
 Ferromagnetic materials are materials
that show strong magnetic properties.
 Examples: iron, nickel, cobalt,
gadolinium, samarium, neodymium

Making, Changing, and Destroying
Magnets
Permanent magnets are made from
materials that keep their magnetism.
 Temporary magnets are made from
materials the easily lose their
magnetism.
 Heating a magnet, stroking a magnet
back and forth with another magnet,
and striking/dropping a magnet can
destroy its magnetism.

Breaking Magnets

If a magnet is broken in two, you end up
with two magnets each with a North and
South pole.
Electromagnetism
Electric Current and Magnetism
An electric current produces a magnetic
field.
 The relationship between electricity and
magnetism is called
electromagnetism.

Solenoids
A solenoid is a coil of wire with a
current.
 The more coils a solenoid has the
stronger the magnetic field.

Electromagnets
An electromagnet is a solenoid with a
ferromagnetic core.
 This type of magnet can be turned on
and off.

Increasing the Strength of an
Electromagnet
Use a stronger ferromagnetic core
 Add more coils to the solenoid
 Wind the coils of the solenoid closer
together
 Increase the electrical current by adding
more voltage.

Uses of Electromagnets

Junkyard Cranes, Circuit Breakers, and
MRI’s just to name a few.