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RE: [MEG_builders] Re: megmania

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  • Fred Epps
    Hi Cyril, ... Right. ... I think the experiment needs to be done. I ll see if I can dig up someone to do it, and then send a report back to the list. ... The
    Message 1 of 13 , Jul 16, 2002
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      Hi Cyril,
      > >
      > > In effect, you are suggesting that the flux of the magnet does
      > > not 'really' move even though a source of flux is changing nearby. I
      > > think this gets into the murky waters of what we mean when we say a
      > > field 'moves'. I suppose you could construct even the field around a
      > > magnet being transported from one end of the table to the other as a
      > > virtual movement, if you squinted at it hard enough.
      > > But the practical question is this: in my example above, if one puts
      > > a wire orthogonally between the bar magnet and the two switched
      > > magnets,
      >
      > Don't you mean the two switched coils?

      Right.
      >
      > > is the induction in the wire due to the B in the wire alone,
      > > or is it due to the B of the wire and the B of the magnet? This seems
      > > to be a simple enough experiment. I would be very surprised if the
      > > presence of the magnet did not affect the induction.
      >
      > I think you will find the induction to be the same whether the magnet is
      > present or not. The magnet wll only affect the induction if it's
      > magnetization changes, i.e. if the applied field (from the coils) is big
      > enough to demagnetize the magnet.

      I think the experiment needs to be done. I'll see if I can dig up someone
      to do it, and then send a report back to the list.
      >
      > > At the very
      > > least, the presence of the magnet causes the flux to pass back and
      > > forth across the wire when it wouldn't otherwise.
      >
      > As you say that depends on what we mean when we say the field 'moves'.
      > Motional inductance involves either the conductor moving
      > relative to a fixed
      > magnetic source or the magnetic source moving relative to a
      > fixed conductor.
      > The above experiment does not meet these criteria.

      The debatable word is 'source'. I don't agree that the source has to move,
      just the flux generated by that source. But let's not debate it any more.
      Let's ask Nature for her opinion.

      Regards,
      Fred
      >
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