Plus and minus poles of magnets

Basically, every magnetic body creates a magnetic field. The field lines of this magnetic field - i.e., the structures indicating the direction and strength of the field - which surround the magnet, illustrate its course. They enter the magnet at the south pole and usually exit again at the opposite north pole. From there they run again in curved lines on the shortest path back in the direction of the South Pole until they come up vertically on its surface.

Since this is a closed system and no clear start and end point can be identified, the roles of the north and south poles of a magnet have been fixed. Whether you designate the ends of a magnet as the plus and minus or the north and south poles is not decisive in everyday use. The plus pole is usually equated with the magnetic north pole.

Where does the term plus-minus magnet come from?

From a scientific point of view, the name is misleading as there are no magnetic charges in the magnetic field of a magnet that can be viewed as separate poles. However, this would be the case in an electrical conductor through which current flows. Instead, the magnetic field of a permanent magnet is a dipole field or, in other words, a magnet with a north and a south pole. Fixed colors are assigned to the plus and minus poles of a magnet for better recognition. The plus pole of a magnet is marked red, the minus pole green.

The alignment of the smallest elementary magnets, which are located inside a magnetic body, during magnetization is based on the plus and minus poles of a magnet. If a south pole of another magnetic body is applied to the north pole of the magnet, the plus and minus poles of the magnets attract each other. The same applies if an external north pole is aligned with the south pole of a magnetic body, whereas the positive and negative poles repel each other. This applies regardless of whether it is an iron body, a ferrite, or a neodymium super magnet.

Whether an object is magnetic and thus has a north and a south pole, from which the surrounding magnetic field develops, depends on the permeability of the respective material. Highly permeable or ferromagnetic materials contain elementary magnets that align with an externally applied magnetic field. In doing so, they are magnetized themselves. This is a phenomenon also known as magnetic influence. In addition, increasing the magnetic flux density increases the strength of the entire magnetic field.

Such ferromagnetic materials include:

  • Iron
  • Nickel
  • cobalt
and alloys of these materials.

There are also magnets that have only one pole?

A magnetic monopole, i.e., a magnet that has only one south or only one north pole, is not yet known. For example, if you split a bar magnet into two halves, the poles that have been separated are created at the newly formed ends - i.e., a south pole as a counterpart to the north pole and vice versa. The effect and direction of the magnetic field - recognizable by the course of the field lines - is immediately adjusted accordingly.

Plus, and minus magnets are based on a dipole field. A so-called magnetic monopole is currently only conceivable at the particle level. For example, electronic particles have been detected in some materials that behave similarly to individual freely moving north and south poles. However, they only occur in pairs, so that they cannot be regarded as free magnetic monopoles either.

Is the north pole a plus or minus pole?

In fact, our earth is also surrounded by a huge magnetic field that emanates from two poles. The reason for this is numerous subterranean currents in the interior of the earth. Accordingly, there is a magnetic north pole and a magnetic south pole on the globe. However, these do not coincide with the geographic north and south poles. Instead, the magnetic pole that can be seen in the north of the world is located a few hundred kilometers from the geographically northernmost point. But this magnetic pole at the geographic North Pole is a plus or minus pole?

The answer is a simple compass with the needle always pointing in the direction of the North Pole. If you now know that the south pole of a magnet is attracted exclusively by a north pole and a north pole exclusively by a south pole, the geographic north pole corresponds to the magnetic south or negative pole of the earth. From this perspective one can imagine the earth as a giant permanent magnet.

Here, too, the designation plus and minus pole can easily be misleading, since strictly speaking it is a magnetic field without charged poles. But the earth has an electric field in addition to the magnetism already discussed. It is itself negatively charged, which is why the assumed field lines meet it, based on the predominantly positively charged atmosphere.