JAMB - Physics (1993 - No. 24)
Which of the following correctly explains why soft iron is proffered to steel in electromagnets? i. soft iron is more readily magnetized than steel. ii. soft iron is more readily demagnetized than steel. iii. soft iron retains magnetism more than steel.
i only
ii and iii only
i and ii only
i, ii, and iii.
Giải thích
Soft iron is more readily magnetized than steel (i): Soft iron can become magnetized more easily and reaches saturation quicker than steel.
Soft iron is more readily demagnetized than steel (ii): Soft iron loses its magnetism more quickly when the magnetic field is removed, which is desirable in applications like electromagnets that need to be turned on and off.
Soft iron retains magnetism more than steel (iii): Soft iron does not retain magnetism as well as steel; that is one of the reasons it is used in electromagnets.
Therefore, i and ii are correct.