(a) State Gauss’ law for magnetism. Explain its significance.
(b) Write the four important properties of the magnetic field lines due to a bar magnet.
OR
Write three points of differences between para, dia, and ferromagnetic materials, giving one example for each

(a) Gauss law for magnetism : If a closed surface is imagined in a magnetic field, the number of lines of force emerging from the surface must be equal to the number entering it. That is, the net magnetic flux out of any closed surface is zero.
Gauss law signifies that magnetic mono poles does not exist.
(b) In a bar magnet, each lines of force, starts from a north pole and reaches the south pole externally and then goes from south pole to a north pole internally. Thus, magnetic line of force forms a closed loop.
2. No two lines of force will never intersect each other. 
3. In a uniform field, the lines are parallel and equidistant from each other.
4. The lines of force are crowded near the poles.
OR