Cutting a magnetic bar in half will not strip off its poles. It will only produce two magnets, each with a north pole that will be attracted to the south pole of the other magnet, and vice versa.
It is this basic property of attraction that makes magnets useful for so many purposes, from holding a party invitation to the fridge to making medical imaging.
But how do these poles arise? Why does a magnet have a north and south pole?
Magnets are “one of the deepest mysteries in physics,” he said. Greg Boebinger (Opens in a new tab)Director of the National High Magnetic Field Laboratory in Tallahassee, Florida. while People have been using magnets for thousands of years (Opens in a new tab)Scientists are still learning new things about how they work.
The basic answer to why magnets have poles lies in the behavior of the electrons. All matter, including magnets, is made of atoms. in every cornThe nucleus is surrounded by one or more negatively charged electrons. Each of these electrons generates its own small magnetic field, which scientists refer to as “spin.” If enough of these small magnetic fields point in the same direction, the material itself becomes paramagnetic.
Related: Why does metal spark in a microwave?
An electron’s “spin” is something of an abstract concept, Boebinger told Live Science. Technically, no one has ever seen an electron spin – it’s too small to see under a microscope. But physicists know that electrons have a magnetic field because they have measured it. And one of the ways this field can be generated is if the electron is spinning. Reverse the direction of rotation, and the magnetic field will reverse.
when possible, The electrons will pair up so that their spin is cancelled (Opens in a new tab), which makes the net magnetism of an atom zero. But in some elements, such as iron, this cannot happen. The number of electrons and the way they are placed around the nucleus means that each iron atom will have a non-paired electron that generates a small magnetic field.
In a non-magnetic material, these individual magnetic fields point in different random directions. In this case, they mostly cancel each other out, so the material is generally not magnetic. But under the right conditions, small subatomic magnetic fields can align in the same direction. One might think of this as the difference between a crowd of people walking around, versus everyone organizing and facing in the same direction. The combination of these very small magnetic fields creates a larger magnetic field – thus the material becomes a magnet.
Many magnets used in everyday life, such as fridge magnets, are known as permanent magnets. In these materials, the magnetic fields of many atoms in the material have become permanently aligned by an external force—such as being placed inside a more powerful magnetic field.
Often, this more powerful magnetic field is generated by electricity. Electricity and magnetism are fundamentally related, because magnetic fields are generated by the movement of electric charges. That is why the spinning electron contains a magnetic field. But scientists can also harness electricity to create very strong magnets Paulo Veracin (Opens in a new tab), a senior scientist at Lawrence Berkeley National Laboratory in California. Running enough current through a coil of wire generates a very strong magnetic field that lasts as long as the current is flowing. These electromagnets are often used in physics research, Veracin told Live Science. It is also used in medical instruments such as magnetic resonance imaging (MRI) machines.
Earth has its own magnetic field too – which is what makes the compass needle work. Scientists have defined the north pole of a magnet as the tip that points to the north pole of the Earth if the magnet rotates freely. But technically, Boebinger explained, this means that Earth’s magnetic north pole is actually a magnetic south pole, as opposite poles attract.
In physical terms, magnetic field lines flow outward from the north pole of a magnet to its south pole, forming a closed loop.
Physicists have also found other arrangements for magnetic poles, Including the quad (Opens in a new tab), where a group of north and south magnetic poles are arranged in a square. One goal remains elusive, Veracin said: No one has yet found a magnetic monopoly.
Electrons and protons are unipolar: they each have a single electric charge, positive or negative. But electrons (and other particles, too) have magnetic poles. Because they are fundamental particles, they cannot be further broken down. This difference between the way particles behave electrically and magnetically has intrigued many physicists, and for some, finding a particle with a single magnetic pole is the holy grail. Its discovery would defy the laws of physics as we currently understand them.
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