7.1.2 Magnetic Fields

In this lesson, we will explore the concept of magnetic fields, their strength and direction, and their relationship to the forces acting on magnets and magnetic materials.

Magnetic Fields

A magnetic field is the region surrounding a magnet where a force acts on another magnet or a magnetic material such as iron, steel, cobalt, and nickel. The force between a magnet and a magnetic material is always one of attraction.

Strength and Distribution of Magnetic Fields

The strength of a magnetic field varies depending on the distance from the magnet, with the field being strongest at the poles of the magnet. The magnetic field strength decreases as the distance from the magnet increases.

Direction of Magnetic Fields

The direction of the magnetic field at any point is given by the direction of the force that would act on another north-seeking pole placed at that point.

Magnetic field lines are visual representations of the magnetic field direction. They extend from the north (seeking) pole of a magnet to the south (seeking) pole of the magnet.

Magnetic Compass

A magnetic compass consists of a small bar magnet that aligns itself with Earth's magnetic field. Earth has its own magnetic field, and the compass needle points in the direction of the Earth's magnetic field lines.

Plotting Magnetic Field Patterns

A compass can be used to plot the magnetic field pattern around a magnet. By placing the compass at various points, you can trace the direction of the magnetic field lines and observe how the strength and direction change from one point to another.

Core of the Earth

• The behaviour of a magnetic compass and the evidence that Earth's core must be magnetic are closely related.
• The fact that the compass needle aligns with Earth's magnetic field indicates the presence of a magnetic field originating from the Earth's core.

Conclusion

Magnetic fields are the regions surrounding magnets where forces act on other magnets or magnetic materials. The use of magnetic compasses demonstrates the existence of Earth's magnetic field, which points towards the magnetic core of the Earth. By learning how to plot magnetic field patterns using compasses, we can visualise the changing strength and direction of magnetic fields around magnets.