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Magnetism
 Electric Motors
Computer Disc Drives
 Alarm Systems
Electricity and Magnetism
What is the difference between MAGNET
and MAGNETIC?
Properties of
Magnets
• Magnets have two
opposite poles.
– north
– south
• Magnets exert forces on
each other.
• The forces depend on the
alignment of the poles.
Magnetism works because the
magnetic force is greater than the
gravitational force.
Magnetic Magnetic forces exist in what we
Field call a “magnetic field”.
http://www.youtube.com/watch?v=uj0DFDfQajw
The number of field lines indicates
the strength of the source of the
magnet.
• Every magnet creates an energy
field
• The field exerts forces on any
other magnet that is within its
range.
Unlike poles of magnets attract
each other and like poles of
magnets repel.
• Magnetic lines of force
NEVER cross.
• Two or more magnetic fields
overlapping COMBINE.
The earth is
like a giant
magnet!
The nickel iron
core of the earth
gives the earth a
magnetic field
much like a bar
magnet.
Types of Temporary Magnets
Magnets
~These magnets tend to lose
their magnetism after a while
EX: Some refrigerator magnets
when dropped again and again
will no longer be attracted to
metal.
Types of Electromagnets
Magnets
~Created when there is
electric current flowing
through a coil of wire
wrapped around a magnet or
metal core.
Permanent
Magnets
Keep their magnetism.
A mixture of iron, aluminum,
nickel, & cobalt.
Natural
Magnets
Found in nature.
Example: lodestone-used in
compasses.
Electricity and Magnetism – how
are they related?
When an electric current passes through a
wire a magnetic field is formed.
What is electromagnetic induction?
Moving a loop of wire through a magnetic field
produces an electric current. This is electromagnetic
induction.
A generator is used to convert
mechanical energy into electrical energy by
electromagnetic induction.
Electromagnetic
Induction
• Process by which a current
is produced by a changing
magnetic field.
• By either moving the
magnet or the wire,
electricity is produced.
• Ex: Generators-used to
convert mechanical energy
into electrical energy by
electromagnetic induction.
Generating • A power plant generator contains a
turbine that turns magnets inside
Electricity
loops of wire to generate electricity.
What are electric motors?
An electric motor is a device which changes electrical
energy into mechanical energy.
MAGLEV TRAINS!!
https://www.youtube.com/watch?
v=aIwbrZ4knpg
Vocabulary!!
ELECTRIC CURRENT
ELECTROMAGNET
ELECTROMAGNETISM
GENERATOR
INDUCTION
MAGNETIC FIELD
MAGNETIC FORCE
MOTOR