Generated by claude-sonnet-4-6 · 2026-06-15 06:47 · grounding rag
Model Answer
(i) Diagram of magnetic field lines around a bar magnet:
```
N ←————→ S
(Field lines emerge from N, curve around, and merge at S; closed curves)
```
(Draw field lines emerging from North pole, curving around, and entering South pole; lines closer near poles showing stronger field.)
Two characteristics of magnetic field lines:
- Field lines emerge from the North pole and merge at the South pole; inside the magnet they go from South to North — thus they are closed curves.
- No two field lines intersect each other, as that would indicate two directions of the field at one point, which is impossible.
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(ii) Right-Hand Thumb Rule:
Imagine holding a current-carrying straight conductor in your right hand such that the thumb points in the direction of current. Then the fingers wrapping around the conductor indicate the direction of magnetic field lines.
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(iii) As we move away from the wire, the concentric circles become larger, meaning the magnetic field decreases. The strength of the magnetic field is inversely proportional to the distance from the wire — farther the point, weaker the field.
Source: Chapter 12 — Magnetic Field and Field Lines (12.1); Right-Hand Thumb Rule (12.2.2)
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Explanation
- For (i): Always draw the diagram with arrows on field lines (N → outside → S). Examiners specifically check: (a) closed curves, (b) no intersection, (c) crowding near poles = stronger field. Pick any two distinct properties.
- For (ii): Learn the exact wording — "thumb points in direction of current, fingers show direction of field." This is a 1-mark statement; keep it precise.
- For (iii): The key idea is: larger circles = same current spread over greater circumference = weaker field. You don't need the formula, but must state that field decreases with distance. This is a common 1-mark inference question.