Magnetic permeability is maximum for

In a permanent magnet at room temperature,

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

Steel is preferred over soft iron for permanent magnets because

Liquid oxygen remains suspended between two pole faces of a magnet because it is

$A$ thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on,the diamagnetic rod is pushed up,out of the horizontal magnetic field. Hence,the rod gains gravitational potential energy. The work required to do this comes from: