CBSE Class 10 Science 2020 · Paper 31/C/1 · Question 24

(a) The bar magnet exerts a magnetic force in the region around it. Each iron filing in this region is magnetised, becomes a tiny magnet, and is turned by this force to lie along the direction of the magnetic field at its position, so the filings arrange themselves along definite curved lines. (b) The pattern demonstrates the magnetic field around the magnet, the region in which its force can be detected. The lines along which the filings align are the magnetic field lines, and the crowding of filings near the poles shows that the field is strongest there. (c) Magnetic field lines are closed curves: outside the magnet they run from the north pole to the south pole, and inside the magnet from the south pole back to the north pole. The filings align along these lines, so near the magnet they appear as closed curves running from one pole to the other.