How does a magnet work?

Magnets are among the most remarkable materials known to man. Although almost everyone has held a magnet at some point, few people understand exactly what happens when a magnet attracts a metal object or why two magnets sometimes repel each other.

Magnetism is a natural phenomenon that has been known for thousands of years. Yet, it plays a greater role today than ever before. Without magnets, modern technologies such as electric motors, loudspeakers, wind turbines, MRI scanners, computers, and electric vehicles could not function.

To understand how a magnet works, we must first look at the invisible phenomenon that surrounds every magnet: the magnetic field.

The magnetic field

A magnetic field exists around every magnet. This field is invisible to the human eye, but it can be demonstrated using iron filings or special measuring equipment.

When iron filings are sprinkled around a magnet, the small metal particles form distinct patterns. These patterns follow the so-called magnetic field lines. They show how the magnetic field spreads around the magnet.

The magnetic field is strongest at the ends of the magnet. These ends are called poles.

North pole and south pole

Every magnet has two poles:

• a north pole
• a south pole

These poles cannot be separated from each other. Even when a magnet is broken in half, two new magnets are created, each again possessing a north and a south pole.

One of the fundamental properties of magnetism is that like poles repel each other, while opposite poles attract each other.

When two north poles are brought together, a repulsive force is created. If a north pole and a south pole are placed opposite each other, they will attract each other.

This principle forms the basis of almost all applications of magnetism.

Why are some materials magnetic?

Not all materials react to a magnet.

Materials such as wood, glass, plastic, and aluminum are hardly affected by magnetic fields. Iron, nickel, and cobalt, on the other hand, react very strongly to magnets.

This difference arises from the way electrons behave within a material.

Electrons constantly move around the atomic nucleus and possess a small magnetic property. In most materials, these minuscule magnetic fields point randomly in all directions, canceling each other out.

In ferromagnetic materials like iron, however, large groups of atoms can align themselves in the same direction. This creates a measurable magnetic effect.

Magnetic domains

Within a piece of iron are billions of tiny regions called magnetic domains.

Within each domain, the magnetic properties of the atoms largely point in the same direction.

In an unmagnetized piece of iron, however, these domains point randomly in different directions. As a result, they largely cancel each other out, and the material does not appear magnetic.

When a strong magnetic field is applied, many of these domains can align themselves in the same direction. At that moment, a magnetic material is created.

In permanent magnets, a large part of this alignment is maintained, even after the external magnetic field has disappeared.

Permanent magnets and electromagnets

Not all magnets work in the same way.

Permanent magnets retain their magnetic properties without requiring energy. Neodymium magnets, ferrite magnets, and AlNiCo magnets are examples of permanent magnets.

Electromagnets work differently. In this case, an electric current is passed through a coil. As long as current flows, a magnetic field is created. As soon as the current is switched off, the magnetic effect largely disappears.

Electromagnets are widely used in motors, relays, loudspeakers, and industrial machinery.

Why are neodymium magnets so strong?

Neodymium magnets are among the most powerful permanent magnets commercially available.

These magnets consist of an alloy of neodymium, iron, and boron. Due to their special crystal structure, they can store an exceptionally large amount of magnetic energy.

As a result, a relatively small neodymium magnet can provide the same force as a much larger traditional magnet.

This explains why modern devices can become increasingly smaller while their performance continues to increase.

The magnetic field decreases with distance

An important property of magnetic fields is that their strength rapidly decreases with increasing distance.

When a magnet makes direct contact with a steel surface, the attractive force is maximal. Even at a few millimeters distance, the effect becomes noticeably smaller.

Therefore, distance and contact surface play an important role in the ultimate holding force of a magnet.

Magnetism in daily life

Although many people primarily associate magnets with a refrigerator magnet, magnetic fields are now used in almost every modern industry.

Magnets play a role in:

• electric vehicles
• wind turbines
• computers
• smartphones
• loudspeakers
• sensors
• MRI scanners
• production machines
• robotics

Almost every form of modern technology uses magnetism in one way or another.

Conclusion

A magnet works by producing a magnetic field. This field exerts forces on certain materials and on other magnets. The operation of magnets is based on the alignment of magnetic domains within a material and the interaction between north and south poles.

Although magnetism is invisible to the human eye, it is one of the most important physical phenomena behind many of the technologies used daily. From simple magnetic closures to advanced electric motors: magnetism plays a crucial role everywhere.