NCERT Solutions for Class 6th Science Chapter 4 Activity 4.6: Let us experiment — A compass needle and a magnet

Book page 69 Updated on2026-09-19

Q1.

The compass needle is also a magnet. Will it show the same behaviour if a magnet is brought closer to it?

Answer

Yes. The compass needle is a small, freely rotating magnet, so it obeys exactly the same rules as a bar magnet — its North pole is repelled by another North pole and attracted by a South pole.

The only difference is that the needle is very light and turns on a sharp pin, so instead of sliding away or moving closer as a whole, it simply swings round (deflects).

Why the needle is a good detector: because it is so free to move, even a weak magnetic influence makes it turn. That is why a compass, and not a heavy bar magnet, is used to test whether a magnetic effect is present.

Q2.

Now slowly bring North pole of the bar magnet close to the North pole of the compass needle as shown in Fig. 4.9a. Observe the compass needle carefully. What do you observe? Does the needle deflect? If yes, in which direction?

Fig. 4.9a, page 69 — redrawn sketch: the North pole of the bar magnet is brought near the North pole of the compass needle.

Answer

Yes, the needle deflects. The North pole of the needle moves away from the approaching North pole of the bar magnet — the needle swings round until its North end points elsewhere.

Magnet's N pole → brought near needle's N pole
Like poles → repulsion
The needle's North end turns away from the magnet.

Why it does not simply run away: the needle is pinned at its centre, so it cannot travel — the only thing it can do with a push is rotate. As soon as the bar magnet is taken away, the Earth's magnetism brings the needle back to the north-south line.

Tip: Move the bar magnet in slowly. If you shove it in quickly the needle spins wildly and you cannot see which way it went first.

Q3.

Now repeat the above step with the South pole of the bar magnet. Do you observe any difference this time?

Answer

Yes — the deflection is now in the opposite sense. The North pole of the compass needle moves closer to the approaching South pole of the bar magnet (Fig. 4.9b).

Pole of the bar magnet brought near the needle's North pole	Poles involved	Behaviour of the needle's North end
North pole (Fig. 4.9a)	N and N — like poles	Turns away (repelled)
South pole (Fig. 4.9b)	S and N — unlike poles	Turns towards the magnet (attracted)

So the compass needle can tell you which pole of an unmarked magnet is which — the pole that pushes the red (north) end of the needle away is a North pole.

Why this matters: it is also the reason a compass must be kept away from magnets, loudspeakers and mobile phones. Any magnet nearby overpowers the gentle magnetism of the Earth and the compass then points to the magnet instead of to the north.

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