ELECTROMAGNETIC
INDUCTION
Book pg 189 – 192
Syllabus 6.15 – 6.16
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STARTER
v  On your Ipad explain how electricity is generated
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Understand how generators create electricity ALL – State how electricity can be created MOST – Describe how electromagne6c induc6on can be increased SOME – Explain generators work in detail
KEYWORDS: Electromagnetic induction,
Generator, coil, wire, magnet
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MOTOR VS GENERATOR
v  Motors use electricity to produce movement
v  Generator make electricity from movement
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LO: Understand how generators create electricity
ELECTROMAGNETIC
INDUCTION
•  Electromagnetic induction is the term used
to describe how electricity is created in a wire.
•  Moving a magnet in a coil of wire is
ONE of only TWO ways that humans know how to
generate electricity
•  The other way is moving a wire in a
magnetic field
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What is electromagnetic induction?
If a wire is moved across a magnetic
field, a potential difference is induced
across the wire and a current is
produced. This is electromagnetic
induction.
Induction also occurs if a magnet is
moved in a coil of wire, or if a coil of
wire rotates in a magnetic field.
In all these methods of inducing a current, the wire and
magnetic field move perpendicular to each other. If they
move parallel to each other, no current is induced.
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Inducing current in a wire
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Magnet and coil: relative movement
Electromagnetic induction depends on relative movement
between the magnet and the coil.
It doesn’t matter whether it is
the coil (top) or the magnet
(bottom) that is moving.
If there is no movement, then
there will be no electromagnetic
induction and no voltage produced
across the ends of the coil.
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Inducing current in a coil
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Varying the size of the induced voltage
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Factors affecting induced current
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SUMMARY:
H OW T O I N C R E A S E T H E I N D U C E D VO LTAG E
Moving a coil in a magnetic field
Moving a magnet into a coil
v  Moving the wire more quickly
v  Moving the magnet more quickly
v  Using a stronger magnet
v  Using a stronger magnet
v  Wrapping the wire into a coil so
v  Using a coil with more turns
that more pieces of wire move
through the magnetic field
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STRENGTH OF CURRENT
v  A voltage and current are generated when a conductor cuts through a magnetic
field
v  The faster the lines are cut, the larger the induced voltage and current
v  No cutting à no voltage or current
v  If direction of motion is reversed, the direction of induced current is reversed
v  Maximum cutting when the coil is parallel to the field à maximum current induced
v  No cutting when the coil is at ​90↑0 to the field
à no current induced
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How do AC generators work?
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AC generator simulation
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WHAT IS THE DIFFERENCE
BETWEEN DC AND AC
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Plenary: True or false?
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