A cylindrical magnet has a length of 15 cm and diameter 3 cm . If it has uniform magnetisation of $4.0 \times 10^3 \mathrm{Am}^{-1}$, then magnetic dipole moment is

A short bar magnet of magnetic moment of $0.15 \mathrm{~J} / \mathrm{T}$ is placed in a uniform magnetic field of 0.4 T . The potential energy of the magnet in unstable equilibrium is

Susceptibility of ferromagnetic substance is

The susceptibility of a magnetism at $$300 \mathrm{~K}$$ is $$1.5 \times 10^{-5}$$. The temperature at which the susceptibility increases to $$4.5 \times 10^{-5}$$ is