Lesson 21.1: Magnetism is a force that acts at a distance

Lesson Focus

Magnetism is a mysterious force that acts from afar, allowing magnets to attract or repel objects without touching them. This lesson explores what makes materials magnetic and reveals how this force shapes our world, from refrigerators to planet Earth.

Learning Objectives

• Discover how magnets push and pull on each other, exploring the fundamental principles of magnetic attraction and repulsion.
• Investigate the atomic properties that make materials like iron magnetic, while others like wood are not.
• Learn why Earth acts like a giant magnet and how its magnetic field protects us from solar particles.

A magnet produces a force called magnetism that acts at a distance, meaning it can pull or push objects without physical contact.

The phenomenon is caused by moving electric charges within the material.

For example, a refrigerator door pulls itself shut just before closing. This non-contact force is key to how magnets work.

A magnet's force is strongest at its magnetic poles: a north pole and a south pole.

When magnets interact, their poles dictate the outcome. Opposite poles (N-S) attract each other, while like poles (N-N or S-S) repel.

This rule explains why you feel a push when trying to force two similar ends together.

The area where a magnet exerts its force is called a magnetic field.

We can visualize this field with lines that flow from the north pole to the south pole. The field is strongest where the lines are densest, which is near the poles.

Why do you think iron filings trace these invisible lines?

In magnetic materials like iron, atoms group into magnetic domains where their tiny magnetic fields point in the same direction. When a material becomes a magnet, all of its domains align, creating one strong, unified field. In non-magnetic materials, atomic fields point randomly and cancel each other out, producing no magnetic effect.

Our planet acts like a giant bar magnet.

This is caused by the movement of molten iron in Earth's core, which creates a massive magnetic field extending into space.

This field is why a compass needle points north and it also protects Earth by deflecting harmful charged particles coming from the sun.