Published: 16 January, 2008

Billions of atoms pulling in the same direction create a magnet

How do magnets work?

Everything that you see around you is made up of billions and billions of atoms. In certain kinds of metals, like iron, cobalt, or nickel, these atoms act like tiny little bar magnets, or as we say, these atoms have a "magnetic moment". However, when you bring billions of iron atoms together in a chunk of iron, the tiny magnetic moments of the individual iron atoms can all add up. You also need to make all of these individual magnetic moments point in the same direction, and when you have done this, that chunk of iron now becomes a magnet. Magnets create a kind of force field that we call a magnetic field, and this magnetic field can push and pull on other magnets, or on flowing electrical currents, like the electrical wires in your house.

However, not all types of atoms have magnetic moments, which is why not all metals are magnets - you have to choose metals like iron or cobalt that have strong magnetic moments. You probably have noticed that magnets can only pick up certain kinds of objects. Magnets can only easily pick up objects that have some amount of iron or other magnetic metal mixed into them - in other words, magnets can only easily pick up or stick to other magnetic materials. For instance, magnets stick to your refrigerator door because it is made of steel, which contains iron, but cannot pick up pennies (which are primarily made of zinc, which is pretty non-magnetic). In reality, nearly all materials, even water or plastic, can get attracted to or repelled by magnets, but only very very weakly (we call these materials either "paramagnetic" or "diamagnetic").

You may have also noticed that magnets have a "north" and "south pole", and this is always true of all magnets. Even the tiny atomic magnetic moment of a single iron atom has both a north and south pole! Magnets create a magnetic field which flows out of the north pole and into the south pole, and this is why the north pole of one magnet will attract the south pole of another magnet, while two north poles will want to repel each other.

Magnets are actually incredibly useful in everyday life. For instance, computers store information on hard drives, which are magnetic disks. Magnets are also essential for electric motors and generators, like those in power plants which provide us with electricity. It also turns out that a flowing electrical current creates a magnetic field, and your cell phones, radios, and laptops use this fact to send and receive wireless signals. Even the earth has a magnetic field because much of the earth's core is made out of iron. Your compass needle is actually a little magnet which likes to align itself with the earth's magnetic field, and we use this tell direction. It turns out that animals like birds actually have tiny magnets in their brain that they use like an internal compass to tell them which way to fly during the migratory season!