Scientists Say: Magnetism

Moving electric charges create this attractive or repulsive force 

iron filings on a table align themselves to point toward and away from the two poles of a bar magnet

Magnetism is what causes iron filings to align themselves along the magnetic field lines of bar magnets like this one.

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Magnetism (noun, “MAG-net-izm”)

Magnetism is a force that can push or pull objects. It is one aspect of a fundamental force of nature called electromagnetism.

Moving electric charges create magnetism. Take the negatively charged electrons in atoms. These electrons spin as they swarm around the centers of atoms, creating tiny magnetic fields. Inside most materials, electrons spin in different directions. So, their magnetism cancels out and the material is not magnetic. But in some materials, such as iron, electrons tend to spin the same way. The particles’ magnetism adds up, and the material is magnetic.

Some objects, like the magnets you might stick on your fridge, are reliably magnetic. Other objects behave like magnets only when they are in the magnetic field of another object. Think of paper clips that stick to a bar magnet. Or iron filings that arrange themselves along a bar magnet’s magnetic field lines. These objects respond to magnetism. But they do not usually make it themselves.

Electric current can also turn some materials into magnets. That’s because an electric current is a stream of moving charges. And moving charges create magnetism. For example, you can turn a coil of wire into a magnet by sending an electric current through it. But the wire will lose its magnetism as soon as the current stops. Another example of current-caused magnetism? Earth. Our planet acts like a giant bar magnet. It has a north and a south pole and a magnetic field that envelops the planet. Earth’s magnetism is thought to arise from electric currents in the liquid metal of its core.

In a sentence

Magnetism can be used to control ferrofluids, which are fluids that contain tiny magnetic particles.

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