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We all know that a current carrying solenoid of copper is a weak temporary magnet and if we wrap it around a soft iron core it becomes a temporary strong magnet i.e. the iron core magnifies the magnetism of the copper solenoid.

In the case of steel, when a current carrying copper solenoid is wrapped around it, it becomes a permanent (long - lasting) weak magnet.

But what would happen if a wire a steel is made a permanent magnet and it is wrapped around a soft iron core. Will the iron become a permanent strong magnet or it will drain the magnetism out of the steel wire.

What will happen and why?

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  • $\begingroup$ Assuming the magnetic field in the wire is along its length, then it will remain in the wire and have little or no effect on the iron core. $\endgroup$
    – R.W. Bird
    Sep 16, 2019 at 18:53
  • $\begingroup$ Are you passing any current through the steel wire? $\endgroup$
    – PM 2Ring
    Sep 16, 2019 at 20:29

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Well I am not sure whether using a steel wire solenoid makes a permanent magnet. My knowledge says that using a steel core in the solenoid(if used at all), or using external magnetic field we can make permanent magnets. I assume that your question is the difference in the behavior of steel and iron in view of magnetization.

To implore the details of it, one finds that the steel becomes permanently magnetized because the different domains of atomic dipoles align themselves in the same direction, when introduced in an external magnetic field. This results in a net magnetic moment, that is permanent due to high retentivity of steel. Steel also has a high value of coercivity, so it needs lot of energy to disorient the domains of the magnet thus making it lose its magnetism.

Hysteresis curves for steel and iron

Introducing a soft iron core increases the strength of the magnet, because of its high value of relative permeability and thus multiplies the existing magnetic field intensity. But it has a higher value of retentivity but very low coercivity, and hence ideal for using in electromagnets as there we need to realign the field intensity with change in direction of current.

Hope this helps.

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