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Electromagnetism
Reversible demonstration alternator
Réf :
292 075
ENGLISH
r
B
N
S
Lenz's law
The coil face moving away from the
north pole of the right magnet is a
south
face,
to
oppose
separation. e < 0
Magnetic flux
The flux is negative increasing.
r
B
r
n
N
S
Lenz's law
The coil face moving towards the
south pole of the left magnet is a
south face to oppose this approach.
e < 0
Magnetic flux
The flux is positive increasing.
The variations of the induction e.m.f. can be summarized in the following table:
positions
Flux Φ
0
dΦ
=
−
> 0 > 0 > 0
e
d
t
3.6 Experimental verification
The experiment is carried out under conditions described and illustrated
above, after marking the polarities of magnets using a magnetized needle.
The coil is connected to an interface connected to the computer (u
coil is rotated using a pen located in the orifice provided for it, in the upper
plate, at the same time as the acquisition is started.
The experimental verification gives:
19
r
B
r
n
N
N
S
S
Lenz's law
The coil face remains a south face
to move away from the right
this
magnet and move towards the left
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 maximum.
mini
0
< 0 < 0 < 0
r
N
S
n
r
n
N
S
maxi
0
0
= e). The
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