How does a compass work?

The earth is a big magnet. The poles of the earth are close to the geographical south pole and the geographical north pole respectively. When the magnets on the earth's surface can rotate freely, they will indicate the north and south because of the nature that like magnets repel and opposite magnets attract. The main part of the compass is the magnetic needle installed on the rotating shaft. Under the action of natural geomagnetic field, the magnetic needle can rotate freely and keep in the tangential direction of magnetic meridian. The north pole of the magnetic needle points to the geographical north pole, and the direction can be distinguished by this property.

1 1 some time ago, it has been found that not only iron blocks can be rubbed on magnets to produce magnetization; Moreover, the red-hot iron sheet can be magnetized by tapping, cooling or quenching, and the iron sheet keeps the north-south direction during operation.

Extended data

Compass invention

The ancestor of the compass appeared in the Warring States period. It is made of natural magnets. It looks like a spoon with a round bottom, which can be balanced on a smooth "field" and can rotate freely. When it is at rest, the handle of the spoon will point to the south. The ancients called it "Sina", and Zheng people took Sina with them when picking jade to make sure they didn't get lost.

Sina consists of a bronze disc and a magnetic spoon made of a natural magnet. The bronze disc is engraved with 24 directions, and the magnetic spoon is placed on the central circular surface of the disc. When it is at rest, the tail of the spoon points to the south.

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