How to observe the magnetic field and identify the magnetic poles?

Generally speaking, the magnetic field of a strong magnet is invisible. This phenomenon also increases the mystery of the magnet and stimulates everyone's curiosity. If you want to visualize the abstract magnetic field and identify the magnetic poles, you can do so with a few simple aids.
1. Magnetic induction line demonstration board
There are vertical, horizontal and three-dimensional varieties. Bar magnets and hoof magnets can be used to demonstrate the formation of magnetic induction lines around them and the formation of magnetic induction lines under different conditions of magnetic pole attraction or repulsion. It is also possible to demonstrate the formation of individual spatial magnetic induction lines around the current magnetic field. Generally made of plexiglass, novel and beautiful, the effect is obvious, both intuitive and can be projected.
Method of use:
A, first shake the demonstration board gently to make the small needle pieces or the small needles in the holes are irregularly arranged, then put the magnet on the demonstration board and tap its plate surface lightly to make the small needle pieces or the small needles in the holes obviously show the magnetic induction lines under the action of the magnetic field.
B, when teaching current magnetic field, 6-9 power supplies are switched on, and magnetic induction lines obviously appear in irregularly arranged needle pieces or small needles in holes. If the direction of the current is changed, the same effect is obtained, and it is concluded that there is a magnetic field around the energized conductor.

2. Magnetic graphics card
It is also a simple and reliable device for detecting magnetic fields. This unique film suspends tiny nickel particles on a thin layer of sticky material that keeps them in line with the magnetic field. It shows the position of the magnet, as well as the number of poles. Simply place the magnetic graphics card on the magnet and the magnetic poles will show dark areas. The light green area is the magnetic field. Magnetic graphics can help us determine the precise position of the magnetic poles, the number of magnetic poles of the magnet, can be relatively easy to findThe "hidden" magnetic field.

3. Magnetic pole detector
Although the magnetic observer cards show the position of the magnetic poles, they do not classify the magnetic poles. If it is important to determine the north or south pole of the magnet, the tool used is a magnetic pole detector. Using the magnetic pole detector to find the magnetic pole is very simple. Just take out the magnet that needs to be detected., Touch the top of the magnetic pole detector to the surface of the magnet,S or N corresponding LED lights will light up. The S light indicates that the magnetic pole in contact is the S pole, on the contrary, it is the N pole of the magnet. With the promotion and popularization of scientific application equipment, magnetic graphics cards and magnetic pole detectors have become common tools for science and technology enthusiasts to detect magnetic poles on a daily basis. As shown in the following figure: