The magnetic permeability '$$\mu$$' a of a paramagnetic substance is :

Find the pole strength of a magnet of length $$2 \mathrm{~cm}$$, if the magnetic field strength $B$ at distance $$10 \mathrm{~cm}$$ from the centre of a magnet on the axial line of the magnet is $$10^{-4} \mathrm{~T}$$.

A bar magnet of length $$6 \mathrm{~cm}$$, is placed in the magnetic meridian with $$N$$ pole, pointing towards the geographical north. Two neutral points, separated by a distance of $$8 \mathrm{~cm}$$ are obtained on the equitorial axis of the magnet. If $$B_H=1.2 \times 10^{-5} \mathrm{~T}$$. Then the pole strength of the magnet is

A bar magnet is oscillating in the earth's magnetic field with a period T. What happens to its period and motion, if its mass is quadrupled?