As a result, an isolated charged particle will usually attract the opposite charge from its surrounding environment to quickly form a neutral system. In addition to electric charge, protons, neutrons, electrons, and neutrinos also have an intrinsic magnetic dipole moment , which means that they act like tiny bar magnets. They have a magnetic axis with a north magnetic pole at one end and a south magnetic pole at the other. Magnetic dipole moment is measured in units of A-m 2 . To understand how magnetism works, it is helpful to think in terms of a magnetic field .
Every magnet creates a magnetic field in the space around it.
When another magnet is placed in the field, it experiences a magnetic force which rotates it so that its magnetic dipole moment aligns with the field, i.e. its poles are opposite to the original magnet's. This is why a compass needle turns towards the Earth's north pole, to align itself with the planet's magnetic field. Note that this alignment tends to cancel out the magnetic field far away, since the second magnet's field is opposite to the first's. A bar magnet is formed from materials such as iron, which can hold the intrinsic magnetic dipoles of electrons so that they all align in the same direction. They then add up to form a large total magnetic dipole moment.