NCERT Solutions Curiosity Chapter 4 Activity 4.3: Let us experiment — Finding Directions
Book page 65 & 66 Updated on2026-09-05
Q1.
Now again rotate the magnet by giving a gentle push at its one end and wait till it comes to rest. Does the magnet rest along the same line?
Answer
Yes. No matter how many times you spin the freely suspended bar magnet, it always settles back along the same line that you had marked on the ground.
How to do it neatly:
Tie the thread exactly at the middle so that the magnet hangs level (horizontal).
Hang it away from iron almirahs, iron grills and mobile phones — they will pull the magnet off course.
Let it stop swinging on its own; do not stop it with your hand.
Mark the two end points on the paper below, join them, and repeat two or three times.
Trial 1 → magnet rests along line PQ
Trial 2 → same line PQ
Trial 3 → same line PQ Conclusion: a freely suspended magnet always comes to rest along one fixed line.
Why it happens: the Earth itself behaves like a giant magnet. Its magnetism turns the hanging magnet until the magnet's North pole faces the Earth's north. Once it is in that position the turning stops, so every trial ends the same way.
Q2.
What direction does this line indicate along which the magnet rests? How can we find it out?
Answer
The line is the north-south line. A freely suspended magnet always rests along the north-south direction.
How to check it without a compass: use the Sun. The Sun rises roughly in the east and sets roughly in the west. Stand in the morning with your right arm pointing towards the rising Sun; then you face north and your back is to the south. Compare this with the line you marked — the two agree.
The four main directions. The red half of the needle points north, the blue half points south — and east lies to the right when you face north.
Why this is so useful: once you know one direction for certain, you know them all. Sailors before the compass used the Pole Star (Dhruva tara) at night, but on a cloudy night — exactly Reshma's problem in the story — the stars are hidden. A magnet works on a cloudy night, in fog and even below deck.
Tip: The end that turns towards north is called the north-seeking pole or simply the North pole; the other end is the south-seeking pole or South pole.
Q3.
Repeat this activity with a small iron bar in place of the bar magnet. What do you observe? Does it always rest along north-south direction?
Answer
Observation: the iron bar stops wherever it happens to stop. It may rest east-west, or slanting, or north-south — and a different direction each time.
No, it does not always rest along the north-south direction.
Object suspended freely
Trial 1
Trial 2
Trial 3
Conclusion
Bar magnet
North-south
North-south
North-south
It is a magnet
Iron bar
Any direction
A different direction
Another direction
It is not a magnet
Why the iron bar behaves differently: a plain iron bar has no poles of its own, so the Earth's magnetism has nothing fixed to turn. A magnet has a North pole and a South pole, and the Earth turns them into place — like a tiny lever being twisted until it lines up.
Tip: This gives us a neat test — only a magnet rests along the north-south direction. Hang a suspicious piece of metal freely; if it stops in the same direction every time, it is a magnet.
Q4.
How can we make our own magnetic compass?
Answer
You can build one in a few minutes with things from home — this is exactly what Activity 4.4 asks you to do.
What you need: an iron sewing needle, a bar magnet, a piece of cork, a glass bowl and water.
Magnetise the needle. Lay the needle on a wooden table. Touch one pole of the bar magnet at one end of the needle and stroke it along the whole length, always in the same direction and always with the same pole. Lift the magnet away at the end, bring it back to the starting end and stroke again. Repeat 30 to 40 times.
Test it. Bring the needle near iron filings or steel pins. If they cling to it, the needle has become a magnet.
Float it. Push the needle horizontally through the cork and float the cork in a bowl of water, keeping the needle above the water level.
Read it. When it stops turning, the needle lies along the north-south line. Your compass is ready.
Why the stroking must be one-way: each stroke nudges the tiny magnets inside the steel needle to face the same way. Strokes in alternating directions would undo each other, and the needle would stay unmagnetised.
Did you know? Long before the modern compass, Indian sailors used the matsya-yantra (or machchh-yantra) — a magnetised fish-shaped piece of iron floating in a vessel of oil. Oil was used instead of water because it is thicker and steadies the fish against the rocking of the ship.