Basic Magnetism

Magnetic Fields

Domains and Hysteresis


Units of Magnetism

Units Of Magnetism

When scientists talk about magnets, magnetism, and magnetic forces, they use different units to describe the different characteristics of magnetism. There are two systems of units based on the metric system that scientists use: MKS (meter-kilogram-second) units and CGS (centimeter-gram-second) units.

A magnetic field is a vector field that permeates space and is capable of exerting a force on other magnets and moving electric charges. The strength of a magnetic field (H) is measured in Amperes/meter in MKS units and in Oersteds in CGS units. One of the largest magnetic fields in the universe belongs to a magnetar, a nuetron star with an extremely high magnetic field. The magnetar SGR 1806-20 has a magnetic field of 2 x 1015 Oersteds. that's 2000000000000000 Oersteds! The earth's magnetic field is about 1/2 of an Oersted. So this magnetar has a magnetic field that is over 1000 trillion stronger than the earth's! The following picture shows an artist's illustration of what a magnetar looks like.


©NASA, CXC M.Weiss

The next characteristic of magnetism that scientist describe is magnetic flux (Φ). Magnetic flux is a measurement of how many magnetic field lines pass through a certain area, and is measured in Weber in MKS units and Maxwell in CGS units. This flux is important because changes in magnetic flux create electric current in any electrical circuit that the magnetic field passes through. Below is illustration of magnetic field lines passing through a surface.

Magnetic FLux

©Oleg Alexandrov

The last main quanitity that scientists often use to describe magnetism is magnetic flux density (B). This is also commonly called magnetic induction, and it is a measure of how responsive a material is to a magnetic field. The magnetic flux density of a magnet is how the strength of a magnet is described most of the time. Magnetic flux density is measured in Weber/meter2 in MKS units or in Tesla in CGS units. The strongest man-made magnet in the world, located at the National High Magnetic Field Laboratory in Tallahassee, Fl, has a strength of about 45 Tesla. That's almost 1 million times stronger than the earth's magnetic field.

World's Strongest MagnetWorld's Largest Magnet©©

This 45 Tesla hybrid magnet (pictured above) is used by scientists from around the world in various research projects. Check out the National High Magnetic Field Laboratory's website to learn more about this incredible magnet and some of the other largest magnets in the world.