FEM induced by a moving magnet... so easy?
- From: nick0039@xxxxxxxxxxxxxx
- Date: Fri, 4 Apr 2008 07:56:33 -0700 (PDT)
I am trying the following experiment:
I would like to estimate the fem produced by falling magnet (at
high=d=70mm) through a tube with a coil at its end.
I use cylinder neodium magnet with remanence of 12T (Bo), radius=6mm,
h=10mm.
I made a coil (area=A=7.5mm, N number of coils=250). Could you please
check if what I am doing is correct?
t0=sqr(2d/g)=0.12s [s] time when the magnet reaches the coil.
B=Bo t/t0 [T] Equation of the magnetic field. B is 0 when the
magnet is outside the coil and it is equal to Bo when it is inside the
coil (at t0)
Phi=NAB=0.053 [Wb] flux of the magnetic field inside the coil
Fem=-dPhi/dt= -NABo/to=-0.43V
Using a scope, the max fem voltage results of -1.2V instead of -0.43.
Am I doing something wrong?
I am not confident about the strength of the magnetic field, since I
am using a small cylinder, I don't know if the B equation is correct.
I looked at the table of the neodium and I found the remanence value
=1.2T. Can I assume this value equal to the magnetic field B of the
magnet?
Could you please help me out?
Thanks in advance
Nick
.
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