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This is a drawing of a magnetic field.
Click on image for full size

# The Magnetic Field

The force of magnetism causes material to point along the direction the magnetic force points. This property implies that the force of magnetism has a direction. As shown in the diagram to the left, the force of magnetism is illustrated by lines, which represent the force. In this diagram, the force points from the positive pole to the negative pole of the magnet. As shown in the diagram, if one side of the magnet is called the positive side, and the other side called the negative side, the force of magnetism flows from the positive side or pole, to the negative pole.

The force of magnetism forces small pieces of iron to line up in the direction the magnetic force points. A compass, in which a sliver of magnetic material can swing freely, is thus forced to point toward the positive pole.

On Earth, the north (positive) pole of the Earth's magnet is in fact at its South geographic pole. A compass needle sure enough indicates North, but if you put a compass needle near a bar magnet, it points AWAY from the north (positve) pole of the bar magnet. This picture shows where the poles are actually found, and also shows that the poles drift over the surface of the Earth over time.

The lines, which represent the force emanating from the magnet, illustrate what is called the magnetic field of the magnet, that is, the force of magnetism coming from the magnet is called the "magnetic field". The magnetic field is strongest where the lines of force come together, and is weakest when the lines of force are far apart. The force of magnetism can exhibit the behavior of more than two poles, but it never exhibits one pole (a mono-pole).

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## Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

## The Sun's Magnetic Field

The Sun has a very large and very complex magnetic field. The magnetic field at an average place on the Sun is around 1 Gauss, about twice as strong as the average field on the surface of Earth (around...more

## Sunspots and Magnetic Fields

Sunspots are caused by extremely strong, localized magnetic fields on the Sun. "Jet streams" of plasma that form deep within the Sun's convective zone produce powerful magnetic fields. When these loops...more

## Basic Facts About Bounce Motion

Not only do particles spiral around magnetic field lines but they also move along the field lines toward the Earth. The crowded magnetic field lines near the poles cause particles to "reflect" and move...more

## Basic Facts About the Effects of Magnetic Fields on Charged Particles

Magnetic fields can cause particles to move in these three ways: Spiral Motion Bounce Motion Drift Motion ...more

## Basic Facts About Spiral Motion

Charged particles cannot easily move across magnetic field lines but are forced to spiral around them. Electrons encirle the field line in one direction, ions in the other direction....more

## The Moon's Magnetosphere

Unlike the Earth, which has a protective shield around it called the magnetosphere, the surface of the moon is not protected from the solar wind. This picture shows the magnetosphere surrounding the Earth,...more

## The Spiral of the IMF

The solar wind is formed as the Sun's topmost layer blows off into space carrying with it magnetic fields still attached to the Sun. Gusts and disturbances form in the solar wind associated with violent...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information.