Magnetism

Magnets helped discover the world as we know it. Earth is like a giant magnet, and its steady pull spun the compasses that pointed explorers like Christopher Columbus across the oceans. Compasses powered navigation, turning the unexplored, ancient world into a modern globe people could understand.

Like gravity, magnetism is an invisible force that streams through our world. But while we can see gravity at work, magnetism is harder for people to detect. Animals find magnetism much more useful: the hidden lines of magnetic fields that bend around the Earth help creatures such as pigeons and turtles to find their way home.

Although magnets seem to push and pull things almost by magic, the strange things they do are actually powered by electrons spinning inside atoms. This is why magnetism is so closely linked to electricity, which is also driven by the movement of electrons. Working together, electricity and magnetism whirl the generators and motors that power almost everything in our modern world, from electric trains to vacuum cleaners.

Discovering magnetism

People discovered magnetism when they found rocks inside the Earth that naturally attracted things. Ancient Greek, Roman, and Chinese people realized they could make compasses by magnetizing needles with these rocks and suspending them over circles marked with directions.

Natural magnet

Lodestone (magnetite) is a naturally magnetic material made from iron oxide. Magnets get their name from Magnesia (now called Manisa, in Turkey), where lodestone was first discovered.

Magnetic forces

Magnets have two different ends called poles, which they use to pull things toward them (attract) or push things away (repel). Although we can't see magnetism, we can watch its effects if we place two magnets close to one another. If the same ends (like poles) of two magnets are placed together, they repel. If opposite ends are placed together (unlike poles), they attract.

Attraction

When the opposite poles of two magnets approach each other, the magnetic field from the north pole of one magnet reaches out to the south pole of the other magnet. This pulls the two magnets together with an attractive force.

Repulsion

If two north poles or two south poles approach each other, their magnetic fields do not link together. This pushes the magnets apart with a repulsive force.

Magnetic materials

Most things that are magnetic are generally made from iron and its compounds or alloys (mixtures of iron with other elements). Magnets themselves are usually made from iron, nickel, cobalt, or other elements in the Periodic Table called the rare earth metals (especially neodymium and samarium).

Magnetic objects

Steel is an alloy of iron, and is used to make cans and paper clips. Some coins contain nickel.

Nonmagnetic objects

These objects don’t respond to magnetic fields or repel them. Plastics aren’t magnetic, nor are aluminum drink cans or brass instruments.

Electromagnetism

Electricity and magnetism are closely linked: each can create the other. British scientist Michael Faraday (1791-1867) was the first person to see how useful this could be. In 1821, he fed electricity into a wire and made it spin around a magnet, inventing the electric motor.

Ten years later, he showed that an electrical conductor moving through a magnetic field could make electricity, inventing the electricity generator. Faraday's work led to our modern world of electric power.

Magnetic field around a wire

When an electric current surges through a wire, it generates rings of magnetic field lines all around it. You can see this by placing a compass near a wire carrying a current. The bigger the current, the stronger the magnetism.

Magnetic field around a coiled wire

When a current flows through a coiled wire, it creates a more complex magnetic field. Each loop makes a field like a single wire and these fields combine, making an overall field pattern similar to one from a bar magnet.