Making a working compass from a magnetized needle and a bowl of water is one of the most satisfying science demonstrations for young children because it produces a genuinely useful instrument from everyday materials. The needle, once magnetized by stroking it with a magnet, aligns itself with Earth's magnetic field and consistently points north. Children who have made a compass understand magnetism and Earth science in a concrete way that no textbook diagram can replicate.

What You'll Need

• A sewing needle or straightened safety pin
• A small, strong magnet (refrigerator magnet or better)
• A shallow bowl or container of water
• A small piece of cork, foam, or a plastic bottle cap to float the needle

Steps

1. Stroke the needle with the magnet 30–50 times, always in the same direction (not back and forth). This aligns the iron atoms in the needle into a magnet.
2. Place the cork or foam piece on the water surface in the bowl.
3. Gently lay the magnetized needle on top of the cork.
4. Watch the needle slowly rotate until it points north-south.
5. Verify by comparing with a phone compass app.

Frequently Asked Questions

Why does the compass needle point north?

Earth has a magnetic field generated by its liquid iron outer core. This field behaves as if a giant bar magnet were buried at Earth's center, with poles near (but not at) the geographic north and south poles. The magnetized needle aligns itself along Earth's field lines — one end points toward magnetic north, the other toward magnetic south. The end that points north is, by convention, the "north pole" of the magnet. Interestingly, Earth's magnetic north pole is actually a magnetic south pole — it attracts the north poles of compass needles.

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