# Magnetic fields

Iron filings are attracted to a bar magnet

A is the region around a where a force acts on another magnet or on a magnetic material. Iron, steel, cobalt and nickel are all magnetic materials and would feel force from a nearby magnet.

## Detecting magnetic fields

A magnetic field is invisible, but it can be detected using a magnetic compass. A compass contains a small bar magnet on a pivot so that it can rotate. The compass needle points in the direction of the Earth's magnetic field, or the magnetic field of a magnet.

Magnetic fields can be mapped out using small :

1. place the plotting compass near the magnet on a piece of paper
2. mark the direction the compass needle points
3. move the plotting compass to many different positions in the magnetic field, marking the needle direction each time
4. join the points to show the field lines

The needle of a plotting compass points to the of the magnet.

The behaviour of a compass shows that the Earth has a magnetic field. The Earth's core, which is made from iron and nickel, produces this magnetic field.

## Drawing a magnetic field

Magnetic field lines around a bar magnet

The diagram shows these key features:

• the never cross each other
• the closer the lines, the stronger the magnetic field (so the magnetic field from a bar magnet is strongest closest to the poles)
• the lines have arrowheads to show the direction of the force exerted by a magnetic
• the arrowheads point from the north pole of the magnet to its south pole