Physics - Magnetism Question with Solution | TestHub

The least value of magnetic field strength required to magnetize is nickel because it is a ferromagnetic material.$\mathrm{Ni}$is a ferromagnetic substance which gets strongly magnetized when placed in an external magnetic field. When external magnetic field${\mathrm{B}}_0$, is applied the magnetic domains orient themselves in the direction of magnetic filed and grow in size.

Hence,$\mathrm{Ni}$requires least value of magnetic strength.$\mathrm{NaCl}$is a diamagnetic material. Its field lines are repelled.