Electricity & Megnetism

Magnet attract iron

A magnet attracts iron when, by applying a magnetic field, its elementary magnets align.

Iron, nickel, cobalt and some metal alloys are said to be ferromagnetic substances or materials, that is, in the presence of a magnetic field they are strongly magnetized, causing the resulting magnetic field to be much larger than the initial one. But why is a piece of iron attracted to the poles of a magnet? Imagine a piece of iron, initially not magnetized, that is placed in the vicinity of a magnet. The magnetic field produced by the magnet magnetizes the iron so that its elementary magnets align in the direction of the applied field, that is, the iron becomes a magnet, thus the attraction between iron and magnet occurs. So, in a more simplified way, we can say that a piece of iron is only attracted by a magnet when, through the application of a magnetic field, the alignment of its elementary magnets occurs.

If we now do the same procedure with a diamagnetic material, that is, materials that are weakly magnetized, such as copper, we will see that the reverse process of what happened with the piece of iron will occur. When applying a magnetic field on this material, its elementary magnets will align in the opposite direction to the direction of the field being applied, then the repulsion between this material and the magnet will occur. This fact was first observed by Faraday, in the 19th century, when he brought a sample of bismuth, also a diamagnetic substance, close to a magnet and saw that it was repelled, contrary to what happened with the pieces of iron he was already exposed to. used to see.

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