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Force exerted by Ferro-magnetic Electromagnet

  1. Aug 4, 2012 #1
    I've been confused for awhile about this and I haven't found any decent explanatory answers.
    I read somewhere that the general formula for finding the force exerted by a solenoid electromagnet could be found by:

    Force = ((N x I)^2 x k x A) / (2 x s^2)

    where N is number of turns of a coil,
    I is the current passing through the coil,
    A is cross-sectional area of the solenoid,
    s is distance between solenoid and external object,
    k is permeability constant (4 x PI x 10^-7)

    Which part of this formula takes into account the inherent magnetic strength of the solenoid? I mean, wouldn't there be a difference in the force exerted if the solenoid was ferromagnetic instead of non-ferromagnetic? Because I also read that a ferromagnetic core like soft iron would amplify the magnetic strength of the electromagnet several hundreds even thousands of times.
    So how could I find the force that an iron core electromagnetic would exert using this formula? Thanks for any help..
  2. jcsd
  3. Aug 4, 2012 #2


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    Homework Helper
    Gold Member

    The force exerted on what? :wink:

    The magnetic field of a solenoid electromagnetic, along its axis, outside the solenoid, is proportional to to NI/s and can be found from the Biot-Savart Law.
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