Unit IIA
Magnetism
Reference: Ch 20-26
Essential Question: How is
magnetism different from electricity?
Magnetic
Properties
Permanent
Magnets

A magnet is a material
that has the ability to
attract and repel other
magnetic materials
 Permanent magnet
– Material that keeps its
magnetic properties,
even when it is not
close to other
magnets—always a
magnet!
Poles
(north and south)
Even
if you chop them in
half, they retain their
magnetic properties
Magnets
exert magnetic
forces on each other
The
forces between
magnets depend on the
alignment of the poles
–Like poles repel
–Opposite poles attract
Magnetic Field

Developed to describe how a magnet
exerts magnetic force
 Every magnet creates an energy field in
the space around it
 The field exerts forces on any other
magnet that is within its range
Permanent magnets & Electromagnets


Creating electromagnets
– Send an electrical current
through a coil of wire
wrapped around some iron
– Current controls the strength
of an electromagnet—more
current, stronger magnet
Uses:Magnetically levitated
trains (monorails) and roller
coasters



Electric currents cause all
magnetism
Electrons move creating
small loops of current
Iron attracts magnets
because its atoms are free
to rotate and align their
north & south poles
Force & Induction

Electromagnetic force
– An electrical and magnetic force between electrical
charges

Electromagnetic induction
– A current is created in a wire by a moving magnet
– The reverse is also true
– Because a moving magnet induces electrical current to
flow
Generators
Electric Motor

Uses a permanent and
an electromagnet.
 The electromagnet
rotates in the
permanent magnet’s
magnetic field
 Creates current.

Generators-make AC
current using a coil of wire
rotating in a magnetic field.
 This produces a current.
 Wire rotated by outside
forces.