Q. Needles $N_{1},\ N_{2}$ and $N_{3}$ are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will
A) Attract $N_{1}\ and\ N_{2}$ strongly but reple $N_{3}$
B) Attract $N_{1}$ strongly, $N_{2}$ weakly and reple $N_{3}$ weakly
C) Attract $N_{1}$ strongly, but reple $N_{2}$ and $N_{3}$ weakly
D) Attract all three of them
Explanation
(b) Ferromagnetic substance have strong tendency to get magnetized (induced magnetic moment) in the same direction as that of applied magnetic field, so magnet attract $N_{1}$ strongly. Paramagnetic substances get weakly magnetized (magnetic moment induced is small) in the same direction as that of applied magnetic field, so magnet attracts $N_{2}$ weakly. Diamagnetic substances also get weakly magnatised when placed in an external magnetic field but in opposite direction and hence, $N_{3},$ is weakly repelled by magnet.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.