There are two sources for B fields, namely fundamental point particles (like the electron), which have intrinsic magnetic fields, and charges of any kind moving with respect to the observer.  The ancient Greeks noticed that there were metallic rocks that were naturally magnetic... lodestones, or permanent magnets.  Each such natural magnet has two poles, North and South.

The direction of the vector field B at a certain location is the direction a compass needle would point, at that location.

Magnetic field lines ALWAYS form closed loops!

The Lorentz Force, F = qvBsinθ. The vector F, and the plane containing v and B are always at right angles to one another. Next Back