There are many types of magnets. For example, if you suspend a horseshoe magnet from a thin thread in the middle of its U-shape, the positions of the magnet's poles when it comes to rest indicate the north and south directions.
Magnets are composed of atoms such as iron, cobalt, and nickel, whose internal structure is unique and inherently possesses a magnetic moment. Magnets can generate a magnetic field and have the property of attracting ferromagnetic substances such as iron, nickel, and cobalt.
A horseshoe magnet is a bar magnet shaped like a U, named after its resemblance to a horseshoe.
The basic method for determining the poles of a magnet is to place the magnet in a magnetic field and observe its movement.
A simpler method is to use another magnet with known polarity and determine the unknown polarity through attraction and repulsion.
The Earth has magnetic properties, and a compass uses the principle of a magnet's movement in the Earth's magnetic field to indicate direction. The key points for determining a magnet's polarity using the Earth's magnetic field are: first, to ensure that the magnet's poles are (approximately) on the same horizontal plane or that the poles can move freely (with very little resistance) in the vertical direction; second, to ensure that the magnet's poles can move freely (with very little resistance) in the horizontal direction. At this point, the magnet's movement in the magnetic field will reveal its magnetic poles. Whether using a suspension thread, floating the magnet, or shaping the magnet into a spoon shape (like an ancient Chinese compass), the purpose is to satisfy these two conditions.
