(a) State Gauss's law for magnetism. Explain its significance.
(b) Write the four important properties of the magnetic field lines due to a bar magnet.

Explanation

(a) Gauss's law in magnetism : Surface integral of magnetic field for any closed gaussian surface is always zero.
`underset(s)(oint)vec(B).vec(ds)=0`
Properties of the magnetic field lines due to a bar magnet
(i) Magnetic field lines never intersect each other. (ii) They flow from south pole to the north pole inside the bar magnet and north pole to the south pole outside the bar magnet.
(iii) Magnetic field lines always make a closed continuous loops.
(iv) The magnetic field lines are crowded near the pole where the fields is strong and far from the magnet they are not crowded as magnetic field is weak.