Re: I wonder

 

I think you have to be careful with how you describe these things, Andrew. The materials are not actually magnetic (i.e., already magnetised) but ferromagnetic (having the ability to be permanently magnetised). Now the thing I don't know is this; if you pass an electric current through a ferromagnetic material, will it become permanently magnetised? I would have thought not (but acknowledge that this may be ignorance talking). My memory of university physics is that, in order for a thing to become permanently magnetised, it had to be placed in a magnetic field, this being generated by something else. The classic example is the electromagnet, in which a current is passed through a coil of wire surrounding a ferromagnetic material. This is not the same as passing a current through the ferromagnetic material. A current-bearing wire will have a magnetic field surrounding it (as shown in Oersted's classic experiment), but will this permanently magnetise the ferromagnetic current carrier? I would have thought very, very slightly, at the most - and only in DC-carrying conductors.