Two thousand years ago, Chinese navigators figured out how magnets could be used in navigation. Some people believe this connection was discovered when someone dropped a piece of natural magnetic rock (called lodestone) into a bucket of water. The rock settled so that it might “point” to north. Every time it was dropped, the rock came to rest in the same direction. This is how compass was discovered.
Things Required:
Sewing needle
Magnet
Plastic foam cup
Pair of scissors
A bowl half with water
Directions:
Carefully remove the circular bottom of a plastic foam cup and place the bottom on the surface of the water. Observe how it floats.
Stroke the magnet along the side of a needle. Remember to stroke only in one direction. Place the magnetized needle on the floating foam bottom.
What happens to the needle and foam?
Now place the magnet along the edge of the bowl. Move the magnet around the bowl. Now what happens to the needle?
This Is What Happens:
The earth has a magnetic field. Magnetic objects placed within this field will react to this attractive force. When the magnetized needle was placed onto the floating foam, it spun freely. Under the influence of the Earth’s field, the needle (and float) rotated to its most stable position. Its north-seeking end pointed to the magnetic North Pole.
