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Was just wondering if someone could clarify this situation:

When I take a Allen wrench and let it come in contact with an iron nail nothing happens. Not really surprising. None of the objects are magnetic. When I take the wrench and let it touch the North end of a magnet and then let it come in contact with the iron nail. Here the wrench becomes magnetic and attracts the nail. When I repeat the previous step but with the south end of the magnet the wrench becomes magnetic and attracts the nail.

I was wondering in terms of functionallity, how functional is the method? Since a weak temporary magnet was created my guess would be the method is low in function. What could the pros and cons be and are there alternative ways to do this that would work even better?

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A ferromagnetic material is made up of many small regions called “domains”. Often, each domain is a single crystal, and the atomic dipole moments tend to line up with the crystal axis. In an un-magnetized sample the crystals and dipole moments are randomly oriented giving a resultant field of zero. If placed in an external magnetic field, the dipoles in some of the domains may be reversed. A stronger field, causes more reversals (up to saturation). If the external field is removed this can leave a remnant magnetization in the material. The strength of the remnant field and its permanence will depend on the alloy used and properties of its crystals. In an AC device, like a transformer or motor, you want a magnetic core with very little remnance to minimize the generation of heat.

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  • $\begingroup$ For the sake of completeness: A piece of magnetizable material of defined form can collect the magnetic field of the permanent magnet into an area and one get a local amplification of the magnetic field. $\endgroup$ – HolgerFiedler May 18 at 4:00
  • $\begingroup$ A piece of ferromagnetic material can be magnetized (partially or fully) by a magnet (or a current carrying solenoid). The resulting field is the vector sum of the two. $\endgroup$ – R.W. Bird May 18 at 14:14

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