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attraction force on electromagnets

Discussion in 'Electronic Basics' started by Camilo Andres Gil Cardona, Oct 1, 2004.

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  1. hi everybody. the question is simple: what's the formula to calculate
    attraction force of an electromagnet (in newtons) ? other question:
    has repulsion force between two magnets, the same value that
    attraction force between those same magnets?
     
  2. Paul Draper

    Paul Draper Guest

    The answer to the second question is yes, provided the N and S poles
    of a given magnet are shaped the same way.

    The answer to the first question is not as simple as you would hope.
    It depends one whether the magnet is a horseshoe magnet, a bar magnet,
    a solenoid, a toroid, whether there's a ferric core,...

    PD
     
  3. Paul Draper

    Paul Draper Guest

    As a personally interesting anecdote, I was once responsible for the
    design, construction, and operation of a 250,000 lb iron-core toroidal
    magnet. I chose to instrument it with a Hall probe, embedded in a thin
    slot in one side. But the slot itself would disturb the field, which I
    had to account for. I proposed a linear model to calculate that,
    superimposing a piece of "negative iron" where the slot was, and
    calculating the total field of the magnet, against which I could
    compare the Hall probe measurement. This approach was deemed clever by
    my professors until a young post-doc pointed out to me, in a fatherly
    conversation in the hallway, that iron core magnets are nonlinear
    beasts and superposition doesn't work, a revelation that left me sick
    to my stomach. Sure enough, the Hall probe read values that were
    inconsistent with calculations and with the backup instrumentation. I
    ended up doing a very complicated lattice-relaxation calculation on a
    mainframe computer to compute the field.

    PD
     
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