The correct option is (c).
Explanation
Permanent magnets exhibit specific physical properties related to their magnetic field lines, interaction with external fields (such as Earth's magnetism), and the stability of their magnetic domains over time. These properties define how magnets interact with materials and their environment.
Statement 1 is Incorrect:
Magnetic field lines can easily pass through non-magnetic materials such as paper, wood, glass, or plastic. These materials have a magnetic permeability similar to that of air or vacuum, meaning they do not significantly obstruct or divert magnetic flux. Magnetic influence is only blocked or shielded by materials with high magnetic permeability (such as soft iron), which divert the field lines through themselves (magnetic shielding).
Statement 2 is Correct:
Bar magnets tend to lose their magnetism over time due to a phenomenon known as self-demagnetization. The free poles at the ends of the magnet create a reverse magnetic field inside the material, which exerts a torque on the magnetic domains, gradually causing them to become misaligned. Magnetic keepers (pieces of soft iron) are placed across the poles to provide a continuous path for the magnetic field lines, thereby preventing this loss of magnetism.
Statement 3 is Correct:
A freely suspended magnet always aligns itself in the geographic North-South direction. This is known as the directive property of magnets. It occurs because the Earth behaves like a giant magnet with its own magnetic field. The north pole of the suspended magnet is attracted to the Earth's magnetic South pole (which is located near the geographic North Pole), causing the alignment.
Key Takeaway:
Magnetic fields penetrate non-magnetic media but can be shielded by ferromagnetic materials. Permanent magnets require keepers to prevent self-demagnetization and naturally align with Earth's magnetic meridian due to the directive property.