13.1 Electromagnetic Induction

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13.1 Electromagnetic Induction
Electromagnetic Induction
• The production of current in a conductor
moving through a magnetic field
Law of Electromagnetic Induction
• A change in magnetic field in the region of a
conductor induces a voltage in the conductor,
causing a induced current.
Faraday’s Experiment
• Two circuits connected by an iron ring
• Primary circuit has a power source which produce a current
that induces a magnetic field in the iron ring.
• The change in magnetic field in the iron ring induces a current
in the secondary circuit.
Factors Increasing
Electromagnetic Induction
• Coiled conductors vs straight conductors
• Increasing number of loops
• Increasing the rate of change of the magnetic field
(sliding magnet in and out quicker)
(Faraday-increase current more
quickly in the primary circuit)
• Increasing the strength of the inducing magnetic field
(stronger magnet)
(Faraday-higher current in primary circuit)
Applications
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Generators
Transformers
Induction cooking (induces an electric current in the pot/pan)
Metal detectors (induce an electric field in metal being
detected)
• Induction chargers (electric toothbrush)
13.2 Lenz’s Law
Direction of Induced Current
• Heinrich Lenz formulated a law to describe
the direction of the induced current.
If the changing magnetic field induces a
current in a coil, the electric current is in such
a direction that its own magnetic field
opposes the change that produced it.
• The coil opposes whatever the magnet is
trying to do
http://k12resources.nelson.com/science/9780176390785/stude
nt/attachments/ott/ani/school_flash.html?file=13_2_a_moving_
magnet_in_a_coil
Drop Tower Rides
• Breaking systems use Lenz’s Law
• Frictional breaks wear quickly
• Electromagnetic breaking system is
more reliable and automatic
• Each seat has a permanent magnet underneath
• The bottom 3rd of the tower has copper strips
mounted vertically on the tower
• Carts fall past the copper strips, magnets induce an
electric current in copper, the current produces a
magnetic field which opposes that of the magnets
on the seats and therefore stops the ride!
Homework
• Pg 591 #’s 1-6 (requires you to go back in the notes and read
about the applications)
• Pg 594 #’s 1-4

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