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Electromagnetism
Reversible demonstration alternator
Réf :
292 075
ENGLISH
3.5 Study of the voltage at the coil terminals at no
load (electromotive force) during time
Consider the coil in rotation relative to the magnets:
r
B
N
In the following study, we refer to the face of the coil from which the normal
originates.
Some positions of the coil as it rotates relative to the magnets are marked at
different times. The views are seen from above and the explanations are
given with reference to:
1. Lenz's law
2. the magnetic flux and variations of the flux
r
n
r
B
N
S
Lenz's law
The coil face moving away from the
south pole of the left magnet is a
north
face,
to
oppose
separation: e > 0
Magnetic flux
The flux is positive decreasing.
r
n
r
B
N
S
Lenz's law
The coil face moving towards the
north pole of the right magnet is still
a north face and opposes this
approach. e > 0
Magnetic flux
The flux is negative decreasing.
18
ω
r
n
S
N
S
r
B
N
S
N
S
Lenz's law
The coil face remains a north face
to move away from the left magnet
this
and
move
magnet. e > 0
Magnetic flux
The flux is null.
r
B
N
S
N
S
Lenz's law
The coil face does not have a
magnetic face. e = 0
Magnetic flux
The flux is minimum.
r
n
N
S
towards
the
right
r
n
N
S
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