Transcript Electric Potential

Electromagnetic Induction
What’s Next?
Electromagnetic Induction
 Faraday’s Discovery
 Electromotive Force
 Magnetic Flux
 Electric Generators
 Lenz’s Law
 Self-Inductance
 Transformers
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What do we know?
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Hans Christian Oersted showed that moving
charges create a magnetic field.
Faraday’s Hypothesis
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If moving charges produced a
magnetic field, could a moving or
changing magnetic field produce a
current?
Faraday’s Discovery
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Faraday discovered that he could induce
current by moving a wire loop through a
magnetic field or moving the magnetic field
through a wire loop.
Faraday’s Discovery is known as
Electromagnetic Induction
Faraday's Discovery
Electromotive Force
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Last week we learned the Lorentz Force.
FB = qvB sinθ = BIL sinθ
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When a conductor moves through a magnetic
field, a force is exerted on these charges causing
them to separate, inducing an EMF.
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Electromotive Force
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We know: W = Fd and V = W/q.
V = Fd/q
Using algebra and solving for F:
F = Vq/d
F = qvB
Set these two relationships equal to one another and then
solve for V, which will now be represented as EMF:
EMF (V) = vBL
Where: L is the length of a conductor passing through a
magnetic field.
EMF = Electromotive Force (Volts)
Electromagnetic Induction
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Why is it important?
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Motors
Generators
Transformers
Electric Generators
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Invented by Michael Faraday.
Convert mechanical energy into electrical
energy.
Similar to an electric motor, but function in an
opposite manner.
Electrical power generation is the foundation by
which electricity is supplied to homes and
businesses around the world.
Electricity is generated in many ways hydroelectric, nuclear, coal, gas, oil fired, wind
solar, geothermal.
Magnetic Flux
What is magnetic flux?
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Like electric flux
A measure of the strength of the magnetic field, B,
passing through a surface perpendicular to the field.
For a bar magnet, the flux is maximum at the poles.
The more magnetic field lines, the higher the flux.
=BAcos
Lenz’s Law
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The induced EMF resulting from a changing
magnetic flux has a polarity that leads to an
induced current whose direction is such that
the induced magnetic field opposes the original
flux change.
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If the magnetic field is increasing, a current will
develop to oppose the increasing magnetic field.
If the magnetic field is decreasing, a current will
develop to create a magnetic field in the same
direction as the one that is decreasing.
A current will form that attempts to keep the
magnetic field constant.
Lenz’s Law abides by the laws of conservation of
energy.
Lenz’s Law
Lenz's Law
Key Ideas
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Electromagnetic induction: is the process
by which current is generated by moving
a conductor through a magnetic field or a
magnetic field through a conductor.
The induced current is maximum when
the relative motion of the conductor is
perpendicular to the magnetic field.
The induced voltage is called EMF (=vBL).
Magnetic flux is a measure of the
strength of the magnetic field passing
through a surface.
Key Ideas
A generator is a device that converts
mechanical energy into electrical
energy.
 Generators are similar to motors.
 Lenz’s Law: The induced EMF
resulting from a changing magnetic
flux has a polarity that leads to an
induced current whose direction is
such that the induced magnetic field
opposes the original flux change.
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