He placed the magnet on the board and floated the board on the water. At this time, it was found that the board carrying the magnet always pointed in the north-south direction. He also placed the iron plate rubbed with the magnet on the above-mentioned wooden board. When the board was placed on the water, the board was also pointed to the north-south direction. Why is the iron plate rubbed with a magnet having a magnet property?
British doctor Gilbert also did the experiment of Bere Zulunus. He cut the magnets in half and placed them on the board and floated them on the water to observe them. They found that the cut magnets still pointed separately. North-south direction. It has also been found that when the south pole of one magnet is close to the south pole of another magnet (or when the north pole is close to the north pole), mutual repelling occurs, and when the south pole of one magnet is close to the north pole of another magnet (or the north pole) When it is close to the South Pole, it attracts mutual attraction. He calls this interaction force a magnetic force.
Gilbert studied why the magnet can point to the north-south direction. It has been experimentally known that the south pole of one magnet is attracted to the north pole of another magnet. He considers whether the earth itself is a large magnet. The poles of the earth are magnetic poles, so that the small magnets on the ground are pointing in the north-south direction.
To this end, Gilbert used a large piece of magnetite to grind a "small earth" model, then found the "small earth" of the South Pole and the North Pole, and used the compass needle for seafarers to observe on the "small earth", compass The needle points to the north and south poles of the "small earth", which is exactly the same as the case where the compass needle points north-south on the ground. Gilbert used this experiment to prove the conjecture that the earth itself is a big magnet.