Identify the paramagnetic substance.

Identify the incorrect statement from the following.

What materials should be used to make permanent magnets?

$A$ perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field $\overrightarrow{B}$. Then the field inside the paramagnetic substance is:

$A$ superconductor exhibits perfect

Ferromagnetic materials used in a transformer must have