A student fixes a sheet of white paper on a drawing board. He places a bar magnet in the centre of it. He sprinkles some iron filings uniformly around the bar magnet. Then he taps the drawing board gently and observes that the iron filings arrange themselves in a particular pattern.
(a) Why do iron filings arrange in a particular pattern ?
(b) What does the crowding of iron filings at the ends of the magnet indicate ?
(c) What do the lines, along which the iron filings align, represent ?
(d) If the student places a cardboard horizontally in a current carrying solenoid and repeats the above activity, in what pattern would the iron filings arrange ? State the conclusion drawn about the magnetic field based on the observed pattern of the lines.
Generated by claude-sonnet-4-6 · 2026-06-15 06:48 · grounding rag
Model Answer
(a) The magnet exerts its influence (magnetic force) in the region surrounding it. The iron filings experience this force, which makes them align in a particular pattern along the magnetic field lines.
(b) The crowding of iron filings at the ends (poles) indicates that the magnetic field is strongest at the poles of the magnet.
(c) The lines along which iron filings align represent magnetic field lines.
(d) The iron filings would arrange in a pattern of parallel straight lines inside the solenoid.
Conclusion: The magnetic field inside a current-carrying solenoid is uniform (the same at all points inside it).
Source: Chapter 12, Sections 12.1 and 12.2.4
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Explanation
- This question tests Activity 12.2 (bar magnet) and 12.2.4 (solenoid). Since it is 3 marks for 4 sub-parts, keep each answer to 1–2 lines.
- Key examiner expectations: (a) mention "force" and "magnetic field"; (b) use the word "strongest"; (c) say "magnetic field lines" exactly; (d) say "parallel straight lines" and "uniform field" — these are the textbook phrases that fetch marks.
- Do not write about direction of field lines in (d) unless asked; the question only asks about pattern and conclusion.