We all know there are two magnetic poles for each permanent magnet,they are N-pole and S-pole.It is impossible to identify the poles from the appearance of a magnet. A specific tool needed to search the poles.There are several methods for knowing magnetic poles, one of ways is based on the principle of the same poles reject each other and different poles attract each other, that is to identify the magnetic poles by using a small bar magnet that its magnetic poles are already known,the magnetic pole that attract with the N-pole of the small bar magnet is S-pole,then this type magnetic pole identifier are designed.
The magnetic pole identifier are also known as magnetic pole searcher. The small bar magnet on the magnetic pole identifier can rotate flexible.The red part and blue part stand for different magnetic poles.When put the magnetic-pole identifier close to a magnet,the small bar magnets from the magnetic pole searcher rotate by the function of magnetic field.We just look at which color of the small bar magnets from magnetic identifier attracted with the searched magnets,so that the magnetic poles are identified.
This type magnetic pole identifier or magnetic pole searcher are mechanical,compared with the electronic pen type magnetic pole identifier, the advantage is much lower cost.