Magnetic field lines around a bar magnet, illustrating the direction and strength of the magnetic field.

Final Answer:
Q1. Magnetism is a non-contact force.
Q2. The unit of force is the newton (N).
Q3. Like poles repel, unlike poles attract.
Q4. The three magnetic metals are iron, nickel, and cobalt.
Q5. Bar magnet.
Q6. Magnetic field lines.
Q7. Left end = N, right end = S (since field lines emerge from N and enter S).
Q8. a) False b) True c) False d) False e) False
Q9. The magnetic field is strongest at the poles (ends) of the bar magnet. We can tell because the field lines are closest together there — denser lines mean stronger field.
Q10. A permanent magnet is a material that keeps its magnetic properties without needing an external magnetic field (e.g., a fridge magnet).
Q11. An induced magnet is a magnetic material that becomes magnetic only when placed in a magnetic field — it loses magnetism when the field is removed.
Q12. Induced magnetism always causes a force of attraction.
Q13. The iron filings align along the magnetic field lines, forming visible curved patterns from one pole to the other.
Q14. Bar ② is unmagnetized iron. Explanation: In the top diagram, bar ① attracts bar ② (A–B attracts C–D), but in the middle diagram, when bar ① is flipped, it still attracts bar ② (A–B attracts D–C). Only an unmagnetized magnetic material (like iron) is attracted to either pole of a magnet. If bar ② were magnetized, flipping bar ① would cause repulsion in one case.
Q15.
a) Two North poles near each other → field lines push away; arrows point outward from both ends, no lines connect them.
b) Two South poles near each other → same as (a), but field lines converge into both ends; again, no connecting lines, lines bend away.
c) North and South near each other → field lines go from N of first to S of second; arrows point from left magnet’s right end to right magnet’s left end.
Q16.
a) Similarity: Both are non-contact forces. Difference: Gravity always attracts; magnetism can attract or repel. Gravity acts on mass; magnetism acts on magnetic materials or moving charges.
b) Similarity: Both follow inverse-square law (strength ∝ 1/r²) for point sources. Difference: Electrostatic force acts between electric charges (positive/negative); magnetism acts between poles (N/S) and requires moving charges or magnetic dipoles. Electrostatic forces can exist with static charges; magnetic forces require motion or intrinsic dipole moments.