Unit IIA Electricity and Magnetism

Unit IIA
Reference: Ch 20-26
Essential Question: How is
magnetism different from electricity?
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
(north and south)
if you chop them in
half, they retain their
magnetic properties
exert magnetic
forces on each other
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
Electric currents cause all
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
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
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

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